Figure 1. Transcriptional gene regulation. (A) Chromatin states based on chromatin profiling of 53 nuclear proteins. Black, Blue, and Green chromatin describe regions with low transcriptional activity and high abundance of repressive proteins, including Polycomb (Pc), Enhancer of zeste [E(z)], Lamin (Lam), Heterochromatin Protein 1 (HP1), Su(var)3–9, among others.¹³ Red and Yellow chromatin describe regions associated with transcription, which include histone acetyltransferases (CAF1), Histone deacetylases (RPD3), chromatin remodelers (BRM) and active chromatin marks (H3K4m3, H3K9Ac, H4K16Ac). (B) Chromatin features associated with transcribed regions that normally include high levels of RNA polymerase II and histone acetylation. In particular, active promoter regions exhibit higher sensitivity to DNaseI, higher amounts of H3K4m3 and lower nucleosome density than upstream or coding regions. Chromatin profiling of HATs and HDACs suggest that these antagonistic complexes co-exist in the Red and Yellow chromatin states in insects, although the functional role(s) associated with this co-localization is unclear.