Sharing the SAGA

Abstract

Transcription initiation is a major regulatory step in eukaryotic gene expression. Co-activators establish transcriptionally competent promoter architectures and chromatin signatures to allow the formation of the pre-initiation complex (PIC), comprising RNA polymerase II (Pol II) and general transcription factors (GTFs). Many GTFs and co-activators are multisubunit complexes, in which individual components are organized into functional modules carrying specific activities. Recent advances in affinity purification and mass spectrometry analyses have revealed that these complexes often share functional modules, rather than containing unique components. This observation appears remarkably prevalent for chromatin-modifying and remodeling complexes. Here, we use the modular organization of the evolutionary conserved Spt-Ada-Gcn5 acetyltransferase (SAGA) complex as a paradigm to illustrate how co-activators share and combine a relatively limited set of functional tools.

Comprehensive Mapping of Histone Modifications at DNA Double-Strand Breaks Deciphers Repair Pathway Chromatin Signatures

“…Time-course experiments confirmed the progressive loss of H2BK120ub upon DSB induction (Figure S3A). Interestingly, SAGA, a prominent chromatin-modifying complex, acetylates histones H3 and H2B and also displays deubiquitinase activity toward H2BK120 (Helmlinger and Tora, 2017). SAGA has also been previously implicated in class switch recombination and response to ionizing radiation (Ramachandran et al., 2016).…”

Co-translation drives the assembly of mammalian nuclear multisubunit complexes

“…SAGA (Spt Ada Gcn5 Acetyltrasferase) is a multisubunit transcriptional coactivator complex, composed of 19 subunits (including a subset of TAFs), required for the transcription of all active genes in yeast 12 . Moreover, the mammalian Transcription and mRNA Export 2 complex (TREX-2) is composed of five subunits, including the subunit ENY2, which is shared with the SAGA complex 13 .…”

Gcn5 and Ubp8 dependent ubiquitylation affects glycolysis in yeast

“…Lysine acetylation, for example, prevents further poly-ubiquitylation on the same residue with a direct impact on several functions including protein turn over and proteasomal degradation [2]. The big multiproteic SAGA complex (Spt-Ada-Gcn5-acetyltransferase) is an epigenetic key regulator of acetylation and establishes the transcriptional competence of gene promoters through the opening of chromatin to the transcriptional machinery [3]. Its relevance is not merely confined to histones modifications but extend far behind to the deposition of PTM marks on non-histone proteins.…”