What do the structures of GCN5-containing complexes teach us about their function?

Transcription initiation is a major regulatory step in eukaryotic gene expression. It involves the assembly of general transcription factors and RNA polymerase II into functional pre-initiation complex at core promoters. The degree chromatin compaction controls accessibility machinery to template DNA. Co-activators have critical roles this process by actively regulating accessibility. Many transcriptional coactivators are multisubunit complexes, organized distinct structural modules carrying multiple activities. first nuclear histone acetyltransferase (HAT) characterized was General Control Non-derepressible 5 (Gcn5). Gcn5 subsequently identified as subunit HAT module Spt-Ada-Gcn5-acetyltransferase (SAGA) complex, which an experimental paradigm for multifunctional co-activators. We know today that catalytic co-activator complexes with specific functions. In review, we summarize recent advances structure Gcn5-containing most notably SAGA, discuss how these new insights contribute better understand their