Structural Biology Programme, Spanish National Cancer Research Centre (CNIO), Calle de Melchor Fernández Almagro 3, 28029 Madrid, Spain.
Genome Damage and Stability Centre, School of Life Sciences, University of Sussex, Falmer, Brighton, UK.
Sci Adv. 2019 May 1;5(5):eaaw1616. doi: 10.1126/sciadv.aaw1616. eCollection 2019 May.
The human R2TP complex (RUVBL1-RUVBL2-RPAP3-PIH1D1) is an HSP90 co-chaperone required for the maturation of several essential multiprotein complexes, including RNA polymerase II, small nucleolar ribonucleoproteins, and PIKK complexes such as mTORC1 and ATR-ATRIP. RUVBL1-RUVBL2 AAA-ATPases are also primary components of other essential complexes such as INO80 and Tip60 remodelers. Despite recent efforts, the molecular mechanisms regulating RUVBL1-RUVBL2 in these complexes remain elusive. Here, we report cryo-EM structures of R2TP and show how access to the nucleotide-binding site of RUVBL2 is coupled to binding of the client recruitment component of R2TP (PIH1D1) to its DII domain. This interaction induces conformational rearrangements that lead to the destabilization of an N-terminal segment of RUVBL2 that acts as a gatekeeper to nucleotide exchange. This mechanism couples protein-induced motions of the DII domains with accessibility of the nucleotide-binding site in RUVBL1-RUVBL2, and it is likely a general mechanism shared with other RUVBL1-RUVBL2-containing complexes.
人类 R2TP 复合物（RUVBL1-RUVBL2-RPAP3-PIH1D1）是 HSP90 共伴侣，对于几种必需的多蛋白复合物的成熟是必需的，包括 RNA 聚合酶 II、小核仁核糖核蛋白和 PIKK 复合物，如 mTORC1 和 ATR-ATRIP。RUVBL1-RUVBL2 AAA-ATPase 也是其他必需复合物（如 INO80 和 Tip60 重塑酶）的主要组成部分。尽管最近进行了努力，但这些复合物中 RUVBL1-RUVBL2 的分子机制仍然难以捉摸。在这里，我们报告了 R2TP 的冷冻电镜结构，并展示了如何将 RUVBL2 的核苷酸结合位点与 R2TP 的客户招募成分（PIH1D1）与其 DII 结构域的结合联系起来。这种相互作用诱导构象重排，导致 RUVBL2 的 N 端片段不稳定，该片段作为核苷酸交换的守门员。这种机制将 DII 结构域的蛋白诱导运动与 RUVBL1-RUVBL2 中核苷酸结合位点的可及性联系起来，它可能是其他包含 RUVBL1-RUVBL2 的复合物共有的一般机制。
