Chaperone-mediated ordered assembly of the SAGA and NuA4 transcription co-activator complexes in yeast

Abstract

Transcription initiation involves the coordinated activities of large multimeric complexes, but little is known about their biogenesis. Here we report several principles underlying the assembly and topological organization of the highly conserved SAGA and NuA4 co-activator complexes, which share the Tra1 subunit. We show that Tra1 contributes to the overall integrity of NuA4, whereas, within SAGA, it specifically controls the incorporation of the de-ubiquitination module (DUB), as part of an ordered assembly pathway. Biochemical and functional analyses reveal the mechanism by which Tra1 specifically interacts with either SAGA or NuA4. Finally, we demonstrate that Hsp90 and its cochaperone TTT promote Tra1 de novo incorporation into both complexes, indicating that Tra1, the sole pseudokinase of the PIKK family, shares a dedicated chaperone machinery with its cognate kinases. Overall, our work brings mechanistic insights into the assembly of transcriptional complexes and reveals the contribution of dedicated chaperones to this process.

Structure of the human SAGA coactivator complex: The divergent architecture of human SAGA allows modular coordination of transcription activation and co-transcriptional splicing

“…Several studies point to the central role of SUPT20H in complex assembly and module association, particularly for hSAGA. Deletion of Spt20, the homolog of SUPT20H in S. pombe , compromised incorporation of Tra1 (homolog of human TRRAP) and decreased DUB module association, but had little effect on the SAGA core ( 23 ). Markedly, depletion of SUPT20H in HeLa cells resulted in a large decrease of observable core and HAT SAGA subunits in ATXN7L3 pulldowns ( 24 ).…”

The TRRAP transcription cofactor represses interferon-stimulated genes in colorectal cancer cells

“…Previous work showed that TTT stabilizes TRRAP in human cells (32,35,36,45). Furthermore, the yeast ortholog of TRRAP, Tra1, also requires TTT and Hsp90 for stability, incorporation into the NuA4 and SAGA co-activator complexes, and function in gene expression (50,81). Here, conditional and rapid depletion of endogenous TELO2 allowed us to better characterize the role of TTT in TRRAP biogenesis and functions in human cells.…”

“…In contrast, the effect of TTT on the incorporation of the TRRAP pseudokinase into the SAGA or TIP60 complexes and on their transcription regulatory roles remains poorly characterized, despite evidence that TTT interacts with and stabilizes TRRAP in mammalian cells (32,35,36,45). We recently showed that, in fission yeast, TTT promotes Tra1 stabilization and complex assembly (50). Interestingly, however, S. pombe apparently lacks orthologs of the R2TP-specific subunits RPAP3 and PIH1D1 (51), suggesting that the mechanism of PIKK complex assembly may differ between species.…”

The SAGA and NuA4 component Tra1 regulates Candida albicans drug resistance and pathogenesis

“…Hsp90 itself is regulated by lysine deacetylases including Hos2, Hda1, Rpd3, and Rpd31, which modulate Hsp90’s role in antifungal drug resistance (58) and morphogenesis (107), and numerous downstream cellular pathways are involved in Hsp90- mediated regulation of virulence and drug resistance, including protein kinase A (PKA), and MAPK signaling pathways (102, 108, 109). Recent work in the model yeast Schizosaccharomyces pombe found that the Tra1 and Tra2 proteins require Hsp90 along with a cochaperone, the Triple-T complex, for integration into the SAGA and NuA4 complexes (39). If the Tra1-Hsp90 interaction is conserved in C. albicans , this interaction may provide at least one rationale for how Hsp90 regulates morphogenesis and virulence.…”

“…It is a member of the PIKK (phosphoinositide-3-kinase-related kinase) family that also includes Tor1, ATM and Rad3-related protein (ATR/Mec1), and the DNA-dependent protein kinase catalytic subunit (DNA-PKcs) (38). As with other PIKKs, Tra1 is incorporated into SAGA and NuA4 in a process that requires Hsp90 and its co-chaperone, the Triple-T complex (TTT complex; (39,40). Tra1 contains four domains: an N-terminal HEAT region, followed by FAT, PI3K, and FATC domains (38,(41)(42)(43).…”