Structural basis for CDK7 activation by MAT1 and Cyclin H

Abstract

CDK7, Cyclin H, and MAT1 form the heterotrimeric CDK activating kinase (CAK) complex. CAK is a vital factor for the two essential processes of transcription and cell cycle control. When associated with the general transcription factor II H (TFIIH) it activates RNA polymerase II by hyperphosphorylation of its C-terminal domain (CTD). In the absence of TFIIH it phosphorylates the T-loop of CDKs that control cell cycle progression. CAK holds a special position among the CDK branch due to this dual activity and the dependence on the MAT1 protein for activation in addition to Cyclin H. We solved the structure of the CAK complex from the model organism C. thermophilum at 2.6 Å resolution. Our structure reveals an intricate network of interactions between MAT1 and its two binding partners CDK7 and Cyclin H providing a structural basis for the mechanism of CDK7 activation and CAK activity regulation. In vitro activity measurements combined with functional mutagenesis show that CDK7 activation can occur independently of T-loop phosphorylation and is thus exclusively MAT1 dependent by positioning the CDK7 T-loop in its active conformation. Finally, our structure of the active CAK with a peptide model provides a molecular rationale for heptad repeat phosphorylation.

Reconstitution and use of highly active human CDK1:Cyclin‐B:CKS1 complexes

“…Phosphorylation of the activation loop of CDK1 occurs in trans by a (CAK). In metazoans, CDK1 is activated by the CDK7:Cyclin‐H kinase, 11,12 which is also implicated, as a module of TFIIH, in the phosphorylation of the C‐terminal domain of RNA polymerase II, as recently depicted 13–16 . Whereas metazoan CAK consists of a CDK7:Cyclin‐H complex, activation of the budding yeast CDK1 (Cdc28) is mediated by the distantly related and monomeric CAK1 (hereafter scCAK1) 17–19 …”

“…In metazoans, CDK1 is activated by the CDK7:Cyclin-H kinase, 11,12 which is also implicated, as a module of TFIIH, in the phosphorylation of the C-terminal domain of RNA polymerase II, as recently depicted. [13][14][15][16] Whereas metazoan CAK consists of a CDK7:Cyclin-H complex, activation of the budding yeast CDK1 (Cdc28) is mediated by the distantly related and monomeric CAK1 (hereafter scCAK1). [17][18][19] Besides phosphorylation, the CDK1:Cyclin-B kinase activity and substrate binding preferences are also regulated by various binding proteins.…”

Molecular cloning and expression analysis of CDK genes during selective and wild populations of juvenile Meretrix meretrix

“…CDK1 along with cyclin B plays a very important role in mitosis and meiosis at the transition of G2/M phase in the eukaryotic cell cycle (Liu et al, 2015; Petrone et al, 2016; Qiu et al, 2008). CDK7 associated with cyclin H comprises the CDK‐activating kinase (CAK), providing the T‐loop phosphorylation required for activation of CDKs 1,2, 4 and 6, which drive cell cycle progression (Peissert et al, 2020; Phinyo et al, 2014; Sava et al, 2020; Schachter & Fisher, 2013). Many studies have identified the role of CDK1 and CDK7 in cell cycle progression and transcription.…”