Figure 6

Model depicting gene priming through hyperacetylation of H4K5. Model depicting the potential role of H4K5ac preceding gene transcription. Sparse acetylation of H4K5 on nucleosomes associated with the promoter region is not sufficient for the recruitment of TFs necessary to initiate transcription. In contrast, hyperacetylation of H4K5 on nucleosomes along the promoter opens chromatin to allow access to large stretches of DNA for the recruitment of TFs proximal to the TSS. Upon binding, TFs may temporarily displace nucleosomes carrying the H4K5ac mark. In the CDS, H4K5ac and H4K12ac proximal to the TSS are necessary for transcriptional elongation by RNA polymerase. H4K5ac may be required throughout the gene body for full extension and/or transcription of splice variants such as Phactr3, whereas H4K12ac may only be needed in the CDS proximal to the TSS. This model proposes that hyperacetylation of H4K5 is needed at the promoter to prime genes for transcriptional initiation but also in the CDS for transcriptional elongation.