HISTONE-LIKE TRANSCRIPTION FACTORS IN EUKARYOTES

Histone proteins have long been recognized as important regulators of eukaryotic gene expression. Condensation of DNA into chromatin by the core (H2A, H2B, H3, H4) and linker (H1, H5) histones effectively repre sses transcription initiation from the promoters of genes that have be en packaged. Recently, eukaryotic transcriptional activators and coact ivators (both positive and negative) resembling core and linker histon e proteins have been discovered. Substantial progress has been made on structural and mechanistic studies of histones and histone-like trans cription factors. Three-dimensional structures solved include the core histone octamer, an archael histone homodimer, two core histone-like subunits of transcription factor IID, a linker histone, and a linker h istone-like transcriptional activator.