Abstract
The Rvb1-Rvb2-Tah1-Pih1 (R2TP) complex is a co-chaperone complex that works together with HSP90 in the activation and assembly of several macromolecular complexes, including RNA polymerase II (Pol II) and complexes of the phosphatidylinositol-3-kinase-like family of kinases (PIKKs), such as mTORC1 and ATR/ATRIP. R2TP is made of four subunits: RuvB-like protein 1 (RUVBL1) and RuvB-like 2 (RUVBL2) AAA-type ATPases, RNA polymerase II-associated protein 3 (RPAP3), and the Protein interacting with Hsp90 1 (PIH1) domain-containing protein 1 (PIH1D1). R2TP associates with other proteins as part of a complex co-chaperone machinery involved in the assembly and maturation of a growing list of macromolecular complexes. Recent progress in the structural characterization of R2TP has revealed an alpha-helical domain at the C-terminus of RPAP3 that is essential to bring the RUVBL1 and RUVBL2 ATPases to R2TP. The RPAP3 C-terminal domain interacts directly with RUVBL2 and it is also known as RUVBL2-binding domain (RBD). Several human proteins contain a region homologous to the RPAP3 C-terminal domain, and some are capable of assembling R2TP-like complexes, which could have specialized functions. Only the RUVBL1-RUVBL2 ATPase complex and a protein containing an RPAP3 C-terminal-like domain are found in all R2TP and R2TP-like complexes. Therefore, the RPAP3 C-terminal domain is one of few components essential for the formation of all R2TP and R2TP-like co-chaperone complexes.
Highlights
The Rvb1-Rvb2-Tah1-Pih1 (R2TP) complex is a co-chaperone complex that works together with Heat shock protein 90 (HSP90) in the activation and assembly of several macromolecular complexes, including RNA polymerase II (Pol II) and complexes of the phosphatidylinositol-3-kinase-like family of kinases (PIKKs), such as mTORC1 and ATR/ATRIP
The RNA polymerase II-associated protein 3 (RPAP3) C-terminal domain interacts directly with RuvB-like 2 (RUVBL2) and it is known as RUVBL2-binding domain (RBD)
R2TP is an HSP90 co-chaperone made of four different subunits, one of which, RPAP3, is a protein containing two tetratricopeptide repeat (TPR) domains that interact with HSP90 and Heat shock protein 70 (HSP70) [2,3,4]
Summary
Heat shock protein 90 (HSP90) is a molecular chaperone that assists the maturation, stability, and assembly of a number of cellular proteins and macromolecular complexes. R2TP is an HSP90 co-chaperone made of four different subunits (see later), one of which, RPAP3, is a protein containing two TPR domains that interact with HSP90 and Heat shock protein 70 (HSP70) [2,3,4]. The R2TP complex works together with HSP90 in the stability and assembly of Pol II [7], small nucleolar ribonucleoproteins (snoRNPs) [8], and complexes of the PIKK family of kinases, including mTOR complexes [9,10]. Evidence suggests that R2TP participates in the assembly and activation of other large macromolecular assemblies, such as U5 snRNP, the sclerosis complex, and possibly several and others [6,11,12]. A protein required the assembly oflater) the kinases of the PIKK family (see later) [3,8,13]
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