CRBM, CNRS, University of Montpellier, Montpellier, France.
BioCampus Montpellier, CNRS, INSERM, University of Montpellier, Montpellier, France.
Nat Commun. 2019 Nov 20;10(1):5237. doi: 10.1038/s41467-019-13243-w.
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.
转录起始涉及大型多聚体复合物的协调活动，但对于它们的生物发生知之甚少。在这里，我们报告了几个原则，这些原则是高度保守的 SAGA 和 NuA4 共激活复合物的组装和拓扑组织的基础，它们共享 Tra1 亚基。我们表明 Tra1 有助于 NuA4 的整体完整性，而在 SAGA 中，它专门控制去泛素化模块 (DUB) 的掺入，作为有序组装途径的一部分。生化和功能分析揭示了 Tra1 与 SAGA 或 NuA4 特异性相互作用的机制。最后，我们证明 Hsp90 和其共伴侣 TTT 促进 Tra1 从头掺入到这两个复合物中，表明 Tra1 是 PIKK 家族中唯一的拟激酶，与其同源激酶共享专用的伴侣机制。总的来说，我们的工作为转录复合物的组装提供了机制上的见解，并揭示了专用伴侣在这个过程中的贡献。
