Sequence-specific Labeling of Nucleic Acids and Proteins with Methyltransferases and Cofactor Analogues

The overall goal of the following experiments is to specifically label DNA and proteins using methyl transferases, which naturally transfer the activated methyl group and the cofactor Sile l methionine called aome to D-N-A-R-N-A. Proteins or small biomolecules. One step labeling is achieved by replacing the natural cofactor omit with synthetic aine cofactors that change the course of the reaction leading to enzymatic coupling of the whole cofactor and therefore covalent labeling of the substrate sequence Specific methyl transferase induced labeling of DNA is demonstrated with the adine specific DNA methyl transferase, M-B-S-E-C one, which couples the biotinylated Aine cofactor six BAZ to the A-G-C-G-A-T recognition sequence leading to sequence, specifically biotinylated, DNA methyl transferase directed transfer of activated groups is use of label protein and is demonstrated using MTAs set seven nine, which transfers a pro pargo group from C eight oin to lysine four of histone H three.

The alkylated lysine residue is chemically labeled by an azi modified Fluor using copper catalyzed click chemistry, thus leading to specifically labeled protein. An advantage of using meth transferases for labeling is that they have the potential to directly target native substrates. I will demonstrate this by sequence specific bioTE elation of plasmid, DNA Meth transferase, catalyzed protein modification with the cofactor analog zin and enables the introduction of a wide variety of reporter groups in two steps.

I will demonstrate this by fluorescence labeling of the protein hisone H three and showing results from labeling H three with biotin. Additionally, double activated cofactor run analogs can be easily synthesized by loading S ail, el homocysteine, the cofactor product after methyl group transfer with various activated alcohols. The synthetic cofactor analogs are purified by reverse phase HPLC, and in some cases it is even possible to separate the epi Mars at sulfur.

Smiling DNA is a sequence specific methyl transferase induced labeling of DNA. Here the concept is demonstrated by labeling PB 3 22 plasmid DNA with six BAZ Aine cofactor, and the adine specific DNA methyl transferase. M-B-S-E-C one begin by hawing the six BAZ at 20 degrees Celsius.

Once thought, repair the reaction mixture on ice. It includes a microgram of plasmid, 60 micromolar of six BAZ, and 10 equivalents of M-B-S-E-C one. HER recognition sequence on the DNA in modification buffer.

Be sure to add the six BAZ and M-B-S-E-C one last. Make sure that there is no AME bound to the meth transferase you are using because the natural cofactor will block the labeling. React For controls.

Substitute the MTAs with water to visualize any non-specific cofactor modifications and add water instead of cofactor to test for natural cofactor in the enzyme concentrate. Now mix the reactions gently with a pipette and incubate them at 55 degrees Celsius for an hour. Towards the end of the incubation, repair an endonuclease mixture on ice by adding 10 microliters of 10 x recombinant tach, one buffer to 80 microliters of water, and then adding 3.3 microliters of recombinant tak one restriction endonuclease.

After the incubation, pull the reactions with a quick spin and then verify the DNA modification to each. Add two microliters of 10 x tak, one buffer, and 28 microliters of the endonuclease mixture. Mix the reactions with gentle pipetting.

Now incubate the reactions at 65 degrees Celsius for half an hour. When the reactions are complete, pull the solution with a quick spin and collect 25 microliters of the reactions into new tubes. To these aliquots, add 2.4 microliters of strep TTR in buffered at one millimolar per monomer of strept adin.

Now incubate this reaction for an hour at 37 degrees Celsius. After the incubation, add five microliters of six x loading buffer to the completed reactions and run out 10 microliters on a 1%agros gel at 80 volts for about an hour. Then visualize the bands mt A is the abbreviation for methyl transferase directed transfer of activated groups.

In this demonstration, the methyl transferase set seven, nine and double activated cofactor C eight. Oin are used to label lysine four of his histone H three. After thawing the components on ice repair 20 microliter reaction mixtures, the assay solution contains modification buffer 10 micromolar of histone H three and added last 10 micromolar of methyl transferases plus 600 micromolar of cofactor.

Make an enzyme control by substituting deionized water for the C eight ON.Also make a cofactor control to visualize nonspecific modifications by including 60 millimolars of ADO met to compete with the synthetic cofactors. Now mix the reactions with slow pipe pesting and check their pH with test strips. Double activated cofactor analogs are stored under C conditions.

Therefore, the pH of your reaction solution can change by adding co factor if necessary at small amounts of 50 millimolar sodium hydroxide to adjust the pH. Now incubate the reactions at 37 degrees Celsius for two hours during the incubation repair. A 12%SDS poly acrylamide gel just before the incubation ends, make 20 microliters of five x click mix containing three milli molar copper sulfate, three milli molar T-H-P-T-A ligand 250 millimolar, sodium ACO bait, and six millimolar Tamara azide.

At the end of the incubation, add five microliters of the click mix to each reaction and mix the reactions slowly by per petting. Protect the reactions from light using foil and incubate them at 20 degrees Celsius for an hour. After an hour, remove the excess chloroform by precipitating the proteins.

Add 75 microliters of methanol, 18.7 microliters of chloroform and 50 microliters of water to each reaction and vortex them briefly After each addition. After preparing each tube, spin them down at 16, 000 G for five minutes. Remove the upper phase of the separation without disturbing the interface layer, which contains the proteins.

Now add 56.3 microliters of methanols, the lower phase and vortex. Next, spin this down to pellet the protein and discard the supinate. Then add 56.3 microliters of methanol.

Again, vortex. Repeat the spin and recover the pellets. Let the pellets dry in their tubes, uncapped and covered with lint-free paper.

Later dissolve the proteins in 20 microliters of SDS loading buffer with loading dye. Rinse the tube walls with the buffer to collect the pellet. Then incubate the tubes at 95 degrees Celsius for 10 minutes.

Once the tubes have called to room temperature, spend them briefly to pull their contents and visualize the proteins by SDS page. Run at 120 volts for about 90 minutes. The smiling reaction was carried out with the DNA methyl transferase M-B-S-E-C one, which modifies the second adenine residue within the double stranded A-T-C-G-A-T sequence and has one recognition site on the PBR 3 2 2 plasmid, which is marked in red to test plasmid labeling.

PB 3 2 2 was challenged with the recombinant restriction ENDONUCLEASE T one, which has seven sites on PB 3 22 marked in green, one of which is included within the M-B-S-E-C one site. When labeling occurs, this site should be protected against cleavage in the gel. This was confirmed.

A new fragment with 683 base pairs appeared demonstrating that there was labeling at the M-B-S-E-C one site. This is seen only in the assay lane, which is lane three. Specificity of the labeling reaction was demonstrated by electromobility shift.

Upon addition of strept adin, the electromobility of the 683 base pair fragment labeled with biotin was retarded. While the mobility of the fragments without the M-B-S-E-C one site was unchanged, or a two step labeling of methyl transferase substrates with double activated eight oh met analogs. The histone H three lysine four methyl transferase set seven nine, and the small C eight ON cofactor were used.

Gel electrophoresis was used for fluorescence detection only the assay lane. Lane one showed a fluorescent band corresponding to histone H three indicating that the side chain of the cofactor was specifically transferred and the modified protein was labeled with the Tamara Flora.Four. The ESI stain serves as a loading control.

All lanes showed the same amount of protein. Methyl transferase substrates can also be labeled with biotin reactions with an azi derived biotin. In place of a Fluor were assay by Western blotting with horseradish peroxidase.

Conjugated Aden successful and specific labeling was seen After watching this video. You should have a good understanding of how to label DNA and protein sequence, specifically with affinity text, Fluor force, or other labels. While attempting this procedure, it is important to remember that other met and its analogs are temperature sensitive.

Always handle them on ice and store them at minus 20 degrees Celsius. I have synthesized double activated. Other MET analogs with the reporter group already built into the side chain and used them to specifically label DNA in one step.

I'm especially thrilled by the prospect of combining different enzymes and report groups for DNA mapping using single molecule techniques. Smiling and NEC are very flexible, and almost any chemical groups can be transferred not only to DNA and proteins, but also to RNA and small using appropriate meth transfers.