To determine the titer, an ELISA was performed using a serial dilution of the H3K27me3S28p antibody (bs-53053R). The antigen used was a peptide containing the histone modifications of interest. By plotting the absorbance against the antibody dilution, the titer of the antibody was estimated to be 1:8,300.


A Dot Blot analysis was performed to test the cross reactivity of the H3K27me3S28p antibody (bs-53053R) with peptides containing other modifications of histone H3 and H4 and unmodified sequences from histone H3. One hundred to 0.2 pmol of the peptides were spotted on a membrane. The antibody was used at a dilution of 1:20,000. The figure shows a high specificity of the antibody for the peptide containing the modifications of interest.


Hela cells were stained with the H3K27me3S28p antibody (bs-53053R) and with DAPI. Cells were fixed with formaldehyde, permeabilized with sodium citrate and Triton X100 and blocked with PBS containing 2.5% BSA. Left side: cells were immunofluorescently labelled with the H3K27me3S28p antibody (diluted 1:200 and incubated for 1 hour at room temperature) followed by goat anti-rabbit antibody conjugated to DyLight 488. Right side: the nuclei were stained with DAPI, which specifically labels DNA. Phosphorylation of H3 on serine 28 is increased during late G2 phase and reaches a maximum in metaphase cells. This may explain the different staining intensities of different cells.


HeLa cells were treated with colcemid to block the cell cycle in metaphase and were fixed with formaldehyde. Chromatin from 10,000 cells was sheared and used for immunoprecipitation (IP). IP was performed with 5 μl of the H3K27me3S28p antibody (bs-53053R). The immunoprecipitated proteins were analyzed by Western blot with the antibody diluted 1:500 in TBS-Tween containing 5% skimmed milk. Lane 1 shows the result of the IP; a negative IP control (no antibody added) and a positive control (sheared chromatin from 10,000 cells) are shown in lane 2 and 3, respectively.


Histone extracts of HeLa cells (15 μg) were analysed by Western blot using the H3K27me3S28p antibody (bs-53053R) diluted 1:250 in TBS-Tween containing 5% skimmed milk. The position of the protein of interest is indicated on the left; the marker (in kDa) is shown on the right. Lane 2 shows the result of the Western analysis with the antibody; lane 1 shows the same analysis after incubation of the antibody with 750 pmol blocking peptide for 1 hour at room temperature.