SAGA complex subunit SGF73

UniProtKB accession:  P53165

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UniProtKB description:  Component of the transcription coactivator SAGA complex. SAGA acts as a general cofactor required for essentially all RNA polymerase II transcription (PubMed:25216679). At the promoters, SAGA is required for transcription pre-initiation complex (PIC) recruitment. It influences RNA polymerase II transcriptional activity through different activities such as TBP interaction (via core/TAF module) and promoter selectivity, interaction with transcription activators (via Tra1/SPT module), and chromatin modification through histone acetylation (via HAT module) and deubiquitination (via DUB module) (PubMed:17090597, PubMed:31969703). SAGA preferentially acetylates histones H3 (to form H3K9ac, H3K14ac, H3K18ac and H3K23ac) and H2B and deubiquitinates histone H2B (PubMed:20395473). SAGA interacts with DNA via upstream activating sequences (UASs) (PubMed:25216679). Also identified in a modified version of SAGA named SALSA or SLIK (PubMed:15932941). The cleavage of SPT7 and the absence of the SPT8 subunit in SLIK neither drive any major conformational differences in its structure compared with SAGA, nor significantly affect HAT, DUB, or DNA-binding activities (PubMed:33864814). SGF73 tethers the DUB module to the rest of the SAGA complex through its central domain and activates the ubiquitin hydrolase UBP8 by maintaining its catalytic domain in an active conformation (PubMed:18488019, PubMed:19226466, PubMed:20395473, PubMed:25526805). SGF73 mediates recruitment of the TREX-2 mRNA export factors SAC3 and THP1 to SAGA, which is crucial to target TREX-2 to the nuclear pore complex (NPC) necessary for export of mRNA (PubMed:18488019). Upon environmental stress, involved in the bypass of the canonical mRNA export process for the immediate export of stress-related transcripts to maintain proteostasis (PubMed:31165730).