DNA Destruction Response and Repair Mechanisms

The balance of the genome is constantly under strike from both endogenous and exogenous DNA damaging agents. These brokers, as well as in a natural way occurring processes such as DNA replication and recombination can lead to DNA double-strand breaks (DSBs). DSBs are possibly lethal therefore eukaryotic cells have evolved a more elaborate pathway, the DNA destruction response, which detects the harm, recruits protein to the DSBs, activates checkpoints to stall cell cycle progression and in the end mediates repair of the destroyed DNA. As the DSBs happen in the context of chromatin, execution of the response is partly orchestrated through the modification of the DNA-bound histone protein. These histone changes are the addition or removal of varied chemical communities or small peptides and function to improve the chromatin framework or to appeal to factors involved in the DNA damage response, and therefore, are especially important in the first phases of the DNA destruction response.

DNA double-strand breaks are fixed by different mechanisms, including homologous recombination and nonhomologous end-joining. DNA-end resection, the first rung on the ladder in recombination, is an integral step that contributes to the decision of DSB repair. Resection, an evolutionarily conserved process that generates single-stranded DNA, is associated with checkpoint activation and is crucial for survival. Failing to regulate and execute this technique results in faulty recombination and can contribute to human disease.

First of all, when DNA is damaged, the cell needs to stop dividing so that it can repair itself and stop further growing of the mutation. When DNA is ruined, cell pattern checkpoints are turned on. You will find checkpoints at G1/S and G2/M limitations, and there is also an intra-S checkpoint. Two kinases, ATR and ATM, controll the checkpoint activation. ATR responds when replication forks are ruined, while ATM picks up double-strand breaks and mutations in chromatin framework. These kinases phosphorylate downstream focuses on in a signal transduction cascade, which in turn causes the cell to pause the dividing process. The checkpoint proteins BRCA1, MDC1, and 53BP1 are probably the proteins needed to transmit the indication to stimulate checkpoints to downstream protein. The checkpoint activations send out a message that the DNA must be restored. DNA repair pathways will then make an effort to repair the destruction. There are different types of DNA repair mechanisms.

A system used to correct DNA is the SOS response. It will involve the RecA necessary protein and the repressor enzyme LexA. Under normal situation, SOS genes are adversely regulated by LexA. When DNA harm occurs, the double-stranded DNA divides into two strings to become in a position to be fixed. When there is certainly single-strand DNA in a cell, RecA is triggered. RecA inactivates LexA. When the quantity of LexA lessens, the repression of SOS genes becomes less, based on the level of LexA affinity for the SOS bins (operator sequences). Some SOS containers bind LexA weakly, so they are simply absolve to work first. Because not every SOS pack binds LexA evenly strong, LexA and RecA therefore can control and activate different repair mechanisms. The first repair device to be induced is nucleotide excision repair (NER). You will see more info about NER down the road. Once the DNA is repaired, the quantity of single-strand DNA lowers. This deactivates RecA, which therefore puts a stop to deactivating LexA. LexA binds to the SOS containers again, and the normal situation is restored.

The SOS response is very common in the bacteria domain name, for example in Escherichia coli. In E. coli, the SOS boxes are 20-nucleotide long sequences near promoters, with a palindromic composition. The structure, duration and structure of SOS boxes varies a lot in different organisms, but it will always be highly conserved. It includes a great deal of information and is considered one of the strongest brief indicators in the genome.

Another kind of DNA repair is immediate reversal. This occurs when cells can chemically reverse the harm done with their DNA. This harm occurs in mere on of the four bases, so the direct reversal mechanism does not need a template. Also, the phosphodiester backbone of the DNA is not cracked. You can find three types of damage that cells can repair with direct reversal.

A common type of cyclobutyl dimer, thymine dimers, can be created when UV light radiates cells, which causes adjacent thymidine bases to create a covalent bond. Photolyase, an enzyme, is triggered when energy is ingested from blue/UV light (300-500 nm wavelength). Photolyase immediately reverses the destruction done by the radiation of UV light. That is called the photoreactivation process.

The second type of damage that can be repaired by the use of immediate reversal, is methylation of guanine bases. The protein methyl guanine methyl transferase (MGMT) directly reverses this damage. A MGMT molecule can only be used once, so this response is stoichiometric and occupies a whole lot of energy.

The last type of DNA injuries that may be chemically reversed is methylation of the bases cytosine and adenine.

When DNA is damaged which can't be chemically reversed, there will vary options. There are many different types of repair when there's destruction in mere one string of the DNA. When one string is broken however the other one is still normal, it can be used as a template. The faulty bottom or a bigger part will be removed, and a new part will be put back, complementary to the other string. When one bottom part is destroyed or absent, the cell uses basic excision repair (BER). BER auto repairs damage induced by oxidation, hydrolysis, alkylation, or deamination. A DNA glycosylase takes out the damaged bottom, and an enzyme called AP endonuclease recognises that something is lacking. AP endonuclease then reduces the Phosphodiester connection, and the lacking part is resynthesized by the DNA polymerase. The nick is then closed with a DNA ligase.

Nucleotide excision repair (NER) is a very important repair system. It can recognize and repair large, helix-distorting lesions. Where BER can only just correct broken bases, NER can remove a larger part of sole stranded-DNA. DNA polymerase then fills the space, using the other strand as a template.

Mismatch repair (MMR) resolves incorrect replication or recombination, when nucleotides are mispaired.

When both strands of DNA are destroyed, for example in a Holliday junction, there is no strand remaining to use as a template to repair the DNA. For double strand destruction, other repair mechanisms have to be used.

Holliday junction

Non-homologous end subscribing to (NHEJ), is a repair system that uses DNA Ligase IV, which sorts a complex with the cofactor XRCC4, to join broken nucleotides mutually. The enzyme DNA ligase IV does indeed this by catalyzing the formation of an internucleotide ester relationship, between the deoxyribose nucleotides and the phosphate backbone. Over the single-stranded tails of the DNA ends are microhomologies, these are short homologous sequences. If these microhomologies are suitable, there usually uses a precise repair. NHEJ is also required for V(D)J recombination, the process that changes the receptors in the disease fighting capability to B-cell or T-cell receptors. In this process, there are hairpin-capped double-strand breaks, they are signed up with again by NHEJ. As a result of this, NHEJ is an important repair system, there are also backup NHEJ pathways in higher eukaryotes. However, NHEJ isn't alway perfect. When nucleotides are lost through the break, you will see nucleotides lacking when these strands are signed up with alongside one another again. Also, the loss of nucleotides can cause the incorrect strands to be connected. This can cause damaging mutations. Overall, NHEJ is a reliable process, which is especially important before the DNA replication of the cell, whenever there are no templates available.

When NHEJ can not be used, MMEJ can be used. MMEJ uses 5-25 bottom part pair microhomologous sequences to align strands before getting started with them. To be able to align them, MMEJ deletes overhanging base pairs and inserts lacking nucleotides, this triggers mutations. Cells is only going to utilize this if NHEJ is unavailable, because MMEJ is less reliable.

If there's a template available, homologous recombination (HR) will be utilized. After DNA replication, a sister chromatid can be used, or a homologous chromosome. This repair method uses an enzymatic process practically identical to the process used for chromosomal crossover during meiosis.

If the destruction in the cell is too severe, apoptosis can be induced. Sometimes DNA harm may cause the cell to malfunction, for example when it is so damaged that the cell can't get enough information from the DNA to continue making all the required enzymes and other important materials. Another reason behind apoptosis can be when the speed of DNA destruction exceeds the ability of the cell to correct the harm.

This is also used to treat cancer. Chemotherapy or radiotherapy overwhelm the capability of the cell to remedy the injury of DNA, triggering the cell to be forced to induce apoptosis. However, this doesn't just affect cancer cells, it also impacts other swiftly dividing skin cells such as stem skin cells in bone marrow. In modern treatments, it's been tried to avoid this, by concentrating the restorative agent around the cancer cells, or by using a medicin against a feature only the cancers cells in the body have.

When DNA repair systems don't work accurately, DNA repair disorders can form. These diseases are extremely dangerous, it's been shown in studies that animals with genetic zero DNA repair frequently have an increased chance to build up tumor, and a shorter life.

Below is a list of genetic diseases induced by defects in repair mechanisms.

Defects in the NER system are accountable for several hereditary disorders, including
  • Xeroderma pigmentosum: hypersensitivity to sunlight/UV, leading to increased skin cancers incidence and premature aging.
  • Cockayne syndrome: hypersensitivity to UV and chemical substance agents.
  • Trichothiodystrophy: sensitive epidermis, brittle hair and fingernails.
  • Mental retardation often accompanies the second option two disorders, recommending increased vulnerability of developmental neurons.
Other DNA repair disorders include
  • Werner's syndrome: premature ageing and retarded growth.
  • Bloom's symptoms: sunlight hypersensitivity, high incidence of malignancies (especially leukemias).
  • Ataxia telangiectasia: level of sensitivity to ionizing radiation and some chemical brokers.

All of the above diseases tend to be called "segmental progerias" ("accelerated aging diseases") because their victims seem elderly and have problems with aging-related diseases at an abnormally young age, while not manifesting all the symptoms of old age.

Other diseases associated with minimal DNA repair function include Fanconi's anemia, hereditary breast cancer and hereditary cancer of the colon.

Wikipedia - DNA repair

DNA repair diseases are hereditary, because of mutations. There's a notable difference between DNA harm and mutation. DNA damage is a physical abnormality in the DNA which can be acknowledged by enzymes. For instance single or two times strand breaks. Since this destruction can be recognized, it can even be restored if there's enough undamaged material fitted to copying remaining. However, mutations cannot be acknowledged by enzymes because a mutation is an alteration in the bottom sequence of both DNA strands. Mutations may survive when the cell is being replicated. DNA injuries are a huge way to obtain mutation, because it causes errors in replication of the cell. Since mutations can not be repaired, they survive, so when these mutations result in a disease, this disease becomes hereditary.

DNA damages aren't only the cause of mutation, but also the reason for aging. Normal mobile metabolism produces byproducts such as reactive air species. These are the cause of DNA damages leading to aging and loss of functional capacity when maturing. A calorie-restricted diet causes less reactive air species and escalates the life time of mammals. This means that that oxidative DNA destruction in a cause of aging.

Overall, DNA damages cause a lot of trouble, and therefore repair mechanisms are incredibly important for success and development.

Background information


Ribbon representation of ubiquitin. Molecular surface of ubiquitin.

Ubiquitin is a regulatory protein that may be within every cell in eukaryotes. Ubiquitination identifies the adjustment after translation of the necessary protein by the covalent relationship of one or even more ubiquitin monomers. The main function of ubiquitin is labeling protein for proteasomal degradation. Besides this function, ubiquitination also control buttons the stability, function, and intracellular localization of a wide variety of proteins.

The ubiquitylation system

Ubiquitin (originally, Ubiquitous Immunopoietic Polypeptide) was first recognized in 1975 as a necessary protein with an anonymous function which was found in every living cell. The essential functions of ubiquitin and the ubiquitination pathway were found out in the first 1980s for which the Nobel Award in Chemistry was awarded in 2004.

The destruction of proteins is as important as their synthesis for the maintenance of necessary protein homeostasis in skin cells. In eukaryotes, the ubiquitin-proteasome system is responsible for a huge part of the protein break down: the small health proteins ubiquitin tags and goals other proteins to visit the proteasome.

With the finding in the late 1980s that the DNA-repair gene RAD6 encodes a ubiquitin-conjugating enzyme, it became clear that proteins modification by having a bond with ubiquitin has a much bigger impact than anyone had thought before. Nowadays, ubiquitinis implicated in a range of individuals diseases, including breast tumors and Fanconi anaemia, which is vital for studies focused on the associations between ubiquitin and DNA-repair. Devastation with the use of ubiquitin plays a crucial part in cell-cycle regulation, DNA repair, cell progress and immune function, as well as in hormone-mediated signalling in plant life. Ubiquitin has been shown to possess numerous non-digestive functions, including participation in vesicular trafficking pathways, legislation of histone adjustment and viral budding.

Proteins can be changed through attachment to ubiquitin and ubiquitin-like protein. Bound ubiquitin regulates the interactions of protein with other molecules, for example binding to the proteasome or recruitment to chromatin. The various ubiquitin systems use related enzymes to add specific ubiquitin-like protein to proteins, and the majority of these attachments are fleeting. There's a lot of evidence suggesting that the modification improved from prokaryotic sulphurtransferase systems or related enzymes. The connection of ubiquitin to protein probably didn't first evolve in eukaryotes, because proteins similar to the enzymes that are involved in the attachment and disattachment of ubiquitin appear to own been formed at the time of the previous common ancestor of eukaryotes.

Given the central role of the ubiquitin system in diverse cellular processes, it isn't astonishing that its dysfunction plays a part in cancer and severe disorders. It is important to understand the ubiquitin system to find suitable treatments for such diseases.

The Ubiquitin Proteasome Pathway has been linked to diseases involving all sorts of mobile activity including
  • Antigen processing
  • Apoptosis
  • Cell circuit and division
  • DNA transcription and repair
  • Immune response and inflammation
  • Neural and muscular degeneration
  • Viral infection
Some genetic disorders associated with ubiquitin are
  • The gene disrupted in Liddle's Syndrome ends in disregulation of the epithelial Na+ route (ENaC) and triggers hypertension.
  • Eight of the thirteen identified genes whose disruption triggers Fanconi anemia encode proteins that form a sizable ubiquitin ligase (E3) organic.
  • Mutations of the Cullin7 E3 ubiquitin ligase gene are associated with 3-M symptoms, an autosomal-recessive progress retardation disorder.

Immuno precipitation

Immunoprecipitation is the strategy of precipitating a protein antigen out of solution using an antibody that specifically binds to the necessary protein. This process can be used to isolate and focus a particular health proteins from an example containing many thousands of different proteins. Immunoprecipitation requires that the antibody binds to beads that may be separated from the rest of the solution.

We've used this somewhat altered strategy: Protein organic immunoprecipitation (Co-IP)

Co-IP functions by selecting an antibody that targets a known health proteins that is thought to be an associate of a larger complex of proteins. By focusing on this known member with an antibody it may become possible to take the entire health proteins complex from the solution and identify the protein that are bound together.

This works when the protein mixed up in sophisticated bind to each other tightly, rendering it possible to take multiple proteins out of solution by latching onto one member with an antibody. That is called a "pull-down". It might be necessary to do several rounds of precipitation with different antibodies.

Repeating the test by targeting different members of the proteins complex helps to double-check the effect. Each round of pull-downs should lead to the recovery of both original known necessary protein, in cases like this ubiquitin, as well as other proteins of the complex. By repeating the immunoprecipitation in this manner, the researcher verifies that each identified person in the protein organic was a valid id.

The two basic methods for immunoprecipitation will be the direct catch method and the indirect catch method. Both methods gives the same end-result with the proteins destined to the antibodies that are on the beads.

The direct method is that antibodies that are specific for a specific protein (or band of proteins) are immobilized on a solid-phase substrate such as microscopic agarose beads. The beads with certain antibodies are then added to the protein mix and the proteins that are targeted by the antibodies are captured onto the beads via the antibodies.

We've used the indirect method. The indirect method is that antibodies that are specific for a particular protein, or a group of proteins, are added right to the combination of protein. The antibodies havent been mounted on a solid-phase support yet. The antibodies are absolve to float throughout the protein mixture and bind their focuses on. After a while, the beads coated in proteins are put into the the combination of antibody and health proteins. At this point, the antibodies, which are actually bound to their targets, will stick to the beads.

With our test the indirect method was preferred since it wasn't known if the concentration of the protein target was low or the relationship of the antibody with the proteins was vulnerable.

The beads need to be separated from the rest of the sample, so that the beads can be washed to eliminate non-bound proteins.

This is performed by spinning the sample in a centrifuge. Following this step, the beads form an extremely small pellet in the bottom of the pipe. The liquid floating above it is carefully removed to not disturb the beads. The buffer solution can then be added to the beads and after mixing, the beads are pulled down of the clean solution by centrifuging the test again.

After that, the beads were washed many times to eliminate any proteins that are not bound to the antibody on the beads. After washing, the proteins were eluted and analyzed using gel electrophoresis and traditional western blotting.

Western blot

The traditional western blot is a method used to find specific protein in a sample. It uses gel electrophoresis to separate denatured protein by the distance of the polypeptide. The proteins are then used in a membrane, where they can be diagnosed using antibodies specific to the mark protein.

We've taken examples from cell culture. The cells were divided by by using a lysate, a solution that damages the cell membrane.

We've used a buffer to loosen the proteins from the cell. Protease and phosphatase inhibitors are put into prevent the digestion of the sample by its enzymes. This was done in a bucket of glaciers to avoid protein denaturing.

The protein of the sample are separated using gel electrophoresis. Parting of proteins may be by isoelectric point (pI), molecular weight, electric charge, or a combination of the factors. The type of the separation depends on the treatment of the sample and the nature of the gel.

The most usual kind of gel electrophoresis uses polyacrylamide gels and buffers packed with sodium dodecyl sulfate (SDS). SDS-PAGE, polyacrylamide gel electrophoresis, keeps polypeptides in a denatured state once they have been cared for with strong lowering agents to remove secondary and tertiary framework and allows separation of proteins by their molecular weight. Sampled protein become covered in the negatively costed SDS and move to the positively recharged electrode through the gel. Smaller protein move faster through the gel and the protein are segregated by their size, which is assessed in kilodaltons (kDa).

Samples are packed into lanes in the gel. The first lane is utilized for the marker, an assortment of proteins with molecular weights that are known, stained to form visible, coloured bands. When voltage is applied across the gel, proteins transfer to it at different speeds. These different rates of motion separate into bands within each street.

In order to make the proteins accessible to antibody detection, they are transferred from within the gel onto a membrane. The membrane is placed together with the gel, and a collection of filter papers placed in addition. The entire stack is positioned in a buffer solution which steps up the paper by capillary action, bringing the protein with it. Another method for transferring the proteins is named blotting and uses an electric current to pull protein from the gel in to the membrane. The proteins move from within the gel onto the membrane while retaining the organization that they had within the gel. Because of this process, the proteins are put over a thin surface level for recognition.

The overall efficiency of transfer of necessary protein from the gel to the membrane can be checked out by staining the membrane.

The membrane has been chosen because of its potential to bind health proteins, and both antibodies and the prospective are protein, so interaction between the membrane and the antibody must be avoided for recognition of the mark protein. This is done by inserting the membrane in a remedy of non-fat dry dairy, with a little bit of Tween, a detergent. The health proteins in the dairy solution attaches to the membrane in every places where the target proteins have never attached. That is done to make sure that there surely is no room on the membrane for the antibody to add apart from on the binding sites of the precise target health proteins when the antibody is added. This reduces "background noise" in the final product of the Western blot, resulting in clearer results, and eradicates phony positives.

During the detection process the membrane is sought out the protein of interest with a altered antibody which is linked to a reporter enzyme, which when exposed to an appropriate substrate drives a colourimetric effect and produces a colour. For a variety of reasons, this customarily takes place in a two-step process, although there are now one-step recognition methods designed for certain applications.

Antibodies are generated when a web host types or immune cell culture is exposed to the protein of interest. Normally, this is part of the immune response, whereas here they may be harvested and used as sensitive and specific diagnosis tools that bind the health proteins directly.

After blocking, a dilute solution of main antibody is incubated with the membrane. The answer is composed of buffered saline solution with a small amount of detergent and powdered milk. The antibody solution and the membrane were sealed and incubated together for 60 minutes.

After rinsing the membrane to remove unbound principal antibody, another antibody is placed on the membrane, fond of a species-specific portion of the principal antibody. This is the extra antibody, and as a result of concentrating on properties, it's called "anti-mouse" or another kinds. Antibodies result from pets; an anti-mouse secondary will bind to nearly every mouse-sourced most important antibody. Several extra antibodies will bind to one primary antibody so the signal will be bigger.

Most commonly, a secondary antibody is utilized to bind a chemiluminescent agent, and the reaction product produces luminescence in proportion to the amount of protein. A very sensitive sheet of photographic film is positioned up against the membrane, and exposure to the light from the effect creates an image of the antibodies bound to the blot.

Another method of secondary antibody diagnosis utilizes a near-infrared (NIR) fluorophore-linked antibody. Light created from the excitation of the fluorescent dye is static, making fluorescent diagnosis a more correct and accurate way of measuring the difference in signal produced by labeled antibodies bound to proteins on a Western blot. Proteins can be accurately quantified because the transmission generated by different amounts of proteins on the membranes is assessed in a static express, as compared to chemiluminescence, in which light is measured in a vibrant state.

The colorimetric diagnosis method depends upon incubation of the European blot with a substrate that reacts with the reporter enzyme that will the secondary antibody. This turns the soluble dye into an insoluble form of an different color that precipitates next to the enzyme and in so doing spots the membrane. Development of the blot is then stopped by cleaning away the soluble dye. Necessary protein levels are evaluated through the intensity of the stain.

Silver Stain

Silver staining is utilized to detect proteins separated by gel electrophoresis.

Protein detection will depend on the binding of sterling silver ions to the amino acid area chains, key the sulfhydril and carboxiyl sets of proteins, followed by lowering to free metallic sterling silver. The protein rings are visualized as places where the reduction occurs and, as a result, the image of necessary protein distribution within the gel is dependant on the difference in oxidation-reduction potential between your gel's area occupied by proteins and the free adjacent sites. Several alteration in the metallic staining process can move the oxidation-reduction equilibrium in a manner that gel-separated proteins will be visualized either as positively or negatively stained bands. The sterling silver amine or alkaline methods will often have lower background and therefore are most hypersensitive but require much longer procedures. Several changes of the silver nitrate staining process have been developed for visualizing protein that can be subsequently digested, recovered from the gel, and subjected to mass-spectrometry (MS) examination, a tool that has been used in blend with gel electrophoresis or chromatographic options for rapid protein id.

After electrophoresis, the gel is removed from the cassette and positioned into a tray containing a proper volume of mending solution. The gel is soaked in this solution instantaneously. This fixation will restrict protein movement from the gel and can remove interfering ions and detergent from the gel. If it is left overnight it may improve the sensitivity of the staining and reduce the background.

Then the gel is washed in 20% ethanol for 20 min. the perfect solution is three times to remove the rest of the detergent ions as well as fixation acid from the gel. Please note: We recommend using ethanol solution instead of deionized water to prevent gel's swallowing. If drinking water is used through the washing step the size of the gel can be restoring by incubation of the gel in 20% ethanol for 20 min. The ethanol solution is cleaned off and the sensitizing solution is added. It's incubated for just two minutes with mild rotation. This will likely improve the sensitivity and the contrast of the staining. The sensitizing solution is washed off and the gel is cleaned twice.

The cold magic staining solution is added and the testtube is shaken for 20 min to permit the silver precious metal ions to bind to proteins. After staining is complete, the staining solution is poured off and the gel is rinsed with a huge volume of deionized water to remove the excess of unbound sterling silver ions. This is repeated. When the gel is washed for more than one minute, it'll remove the gold ions from the gel leading to reduced sensitivity.

The gel is rinsed quickly with the developing solution. A fresh portion of the growing solution is added and the proteins image is produced by incubating the gel in growing solution. The response can be ceased when the desired strength of the rings is come to.

The reduction reaction is stopped by adding terminating solution directly to the gel that is still immersed into growing solution. the gel is softly moved in the perfect solution is. Moist gels can be kept in 12% acetic acid at four degrees Celsius in sealed plastic luggage or put in the drying solution for 2 time before vacuum drying, which is exactly what we've done.

The experiments


To optimise the technique to separate ubiquitinated proteins from the other proteins by using ubiQ beads and displaying them by using antibodies. Showing the efficiency of the parting utilizing the western blot and show the specificity by using the silver stain technique.


The concentration was on preventing the DUB enzyme, which is an enzyme that can take the ubiquitin off of the proteins. This means that the E3 enzyme, which binds the ubiquitin to the substrate, can bind all the ubiquitin to the target substrates. The ubiquitin will add itself onto the beads. When the sample is washed, all the loose proteins will be eliminated from the test. The ubiQ beads are divided in three parts that may undergo a new treatment. The first one will be boiled; the next one eluted with an acidic water; the third one will be eluted with SDS. These three methods will need the ubiquitin destined protein from the ubiQ beads therefore the results can be assessed. The protein that weren't ubiquitinated will be utilized as an input sample alongside the Hela lysate without any proteins in it. The source samples are being used to get rid of background static on the gel scan.


A large area of the ubiquitin will bind to the ubiQ beads and will stay in the sample. This will be made noticeable with several different techniques. The boiled test will have less ubiquitinated proteins, because the protein will denaturize due to high temperature and a large part won't be designed for further research.

Materials and methods

Urea is a robust health proteins denaturant, that disrupts the noncovalent bonds in the protein. Urea may be used to raise the solubility of some protein.

In lysis buffers, NEM is utilized to inhibit deubiquitination of protein for Western Blot examination.

MG132 is a specific, strong, reversible, and cell-permeable proteasome inhibitor. It reduces the degradation of ubiquitin-conjugated protein.


Lyse skin cells and prepare sample for immunoprecipitation.

Pre-clear the test by moving the test over beads that are not coated with antibody to absorb any proteins that non-specifically bind to the beads.

Incubate solution with antibody from the protein appealing. Antibody is mounted on solid support after this step.

Continue the incubation to permit antibody-antigen complexes to create.

Centrifuge the test, removing the perfect solution is on the pellet.

Wash the sample many times.

Spin each time between washes and then take away the fluid above the pallet.

  • After final rinse, remove the maximum amount of fluid as possible.
  • Take proteins from solid support by using SDS sample loading buffer.
  • Analyze the antigens that stay with SDS PAGE

Gel staining

  • The first street is used to insert the marker
  • Samples are filled into wells in the gel.
  • Voltage is applied on the gel
  • The gel is remaining in a much cooler over night with the voltage on

Western Blot

  • The membrane is positioned together with the gel
  • a stack of filter papers placed on top of that
  • The entire stack is located in a buffer solution
  • an electric current is utilized to pull protein from the gel in to the membrane

Silver stain

  • place the gel in to the correcting solution and leave it overnight
  • wash the gel with 20% ethanol for twenty minutes
  • wash the gel three times with deionised water
  • add the sensitizing solution, leave it on the roller for two minutes
  • wash the gel two times with deionised water
  • add the gold stain and shake for twenty minutes
  • wash the gel with deionised water
  • wash the gel shortly with producing solution
  • add new growing solution and put the testtube on the roller for ten minutes
  • the gel is now ready for scanning and additional use


The results from the inhibitor test can be described because through the experiment, the extracting of non targeted proteins wasn't specific enough, because there are a few protein in the results that are recognized to have no effect with ubiquitin but can be identified in the inhibitor test by figuring out them by their weight in kDA with use of the marker.

The results from the silverstain can be discussed by considering the adhesion of the gold to the ubiquitinated proteins. You can find no results in the lanes where the ubiquitinated proteins had been loaded. Which means that the metallic stain method is not succesful in combo with the ubiquitinated protein.


During our internship at Erasmus, we've spent time on using different methods of separating the ubiquinated proteins. We've used the western blot method and the silver precious metal stain method. Through the test out the traditional western blot, we accidentally packed the sample in the wrong lane, which resulted in a mix-up with the results. This mistake couldn't be corrected, but we noticed it whenever we viewed the results.

The silver stain shouldn't have had the result we had, because the metallic is supposed to attach itself to the receptors on the protein. We have no idea exactly why we'd this result. It probably has something to do with a step we had neglected. We've also cultivated cells, however in one of the two petridishes, a group of cells had perished, which induced a strange draw in the cell culture. We'd to work in a sterile pantry where we had to wear gloves as to not contaminate the cell culture that could ruin our test. The skin cells we cultivated the first day were used in the following experiments. we performed two experiments and three scans of the test. We did an alternate test on the western blot by putting a second cover of antigens onto it with luminescent features. This empowered us to look at the sample by using electrochemiluminescence and the photographic papers which were put on the sample newspaper and was developed. We had the chance to attend to a meeting which shed light on the other ongoing experiments at Erasmus, but the given information was hard to grasp for the major part. We discovered a great deal of techniques that are generally used in the lab and this has benefited us in our coursework at college.

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