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Updated: Aug 6, 2026

Studying Proteolysis of Cyclin B at the Single Cell Level in Whole Cell Populations
Published on: September 17, 2012
Interaction between cyclin T1 and SCF(SKP2) targets CDK9 for ubiquitination and degradation by the proteasome
R E Kiernan1, S Emiliani, K Nakayama
1Laboratoire de Virologie Moléculaire et Transfert de Gène, Institut de Génétique Humaine, UPR1142, Montpellier, France. rkiernan@igh.cnrs.fr
Abstract:
CDK9 paired with cyclin T1 forms the human P-TEFb complex and stimulates productive transcription through phosphorylation of the RNA polymerase II C-terminal domain. Here we report that CDK9 is ubiquitinated and degraded by the proteasome whereas cyclin T1 is stable. SCF(SKP2) was recruited to CDK9/cyclin T1 via cyclin T1 in an interaction requiring its PEST domain. CDK9 ubiquitination was modulated by cyclin T1 and p45(SKP2). CDK9 accumulated in p45(SKP2-/-) cells, and its expression during the cell cycle was periodic. The transcriptional activity of CDK9/cyclin T1 on the class II major histocompatibility complex promoter could be regulated by CDK9 degradation in vivo. We propose a novel mechanism whereby recruitment of SCF(SKP2) is mediated by cyclin T1 while ubiquitination occurs exclusively on CDK9.
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