Practice question

Effector proteins interpreting histone code contain specific reader modules. Bromodomain, originally identified in Drosophila Brahma chromatin remodeling complex, forms four-helix bundle with deep hydrophobic pocket specifically accommodating acetyl-lysine side chain, preferentially H3K14ac, H3K27ac, H4K16ac. Binding recruits transcription initiation factor TFIID, SWI/SNF remodeler and p300 acetyltransferase to acetylated active chromatin stimulating gene expression. Chromodomains recognize methyllysine, 14-3-3 binds phosphoserine, no specialized domain uniquely recognizes ubiquitin alone. Bromodomain inhibition by small molecule JQ1 displaces readers blocking oncogenic transcription and inflammation, highlighting therapeutic importance for active chromatin.