Example of the most common pattern for histone and polymerase modifications at the 3′ ends of expressed genes. Chromatin IP results from the chromosome 22q12-q13 region are displayed with the Integrated Genome Browser (IGB) on Human Assembly 7. FBXO7 gene is annotated at this locus. Two antibody groups were used: Group A, human histone modifications; Group B, various phosphorylation states of human PolII. All the chromatin immunoprecipitates were prepared from HeLa cells unless starred to indicate the results were from K562 cells. The information about antibodies used for the data in Figs. 5, 6, 7, 8 is listed in Table 3.The first row shows the RNA polyadenylation signal, which was detected by the 3′ end enrichment method. This 3′ end signal corresponds exactly to the reported 3′ end of the mRNA (RefSeq). Dimethylation of histone 3 lysine 4 extends over a broader region than trimethylation of lysine 4. PolII serine 5 phosphorylation always shows a peak at the 5′ end of the gene. As expected, serine 2 phosphorylation extends through the body of the gene and beyond the poly(A) site. The signal increases just before disappearance of the polymerase from DNA, indicating RNA polymerase pausing occurs before release. Histone 3 K36 trimethylation tracks with PolII serine 2 through the body of the gene; however, just beyond the poly(A) site, trimethylation begins to decrease and apparently becomes uncoupled from serine 2 phosphorylation.
