Commentary to: The cyclin-dependent kinase (CDK) Family member PNQALRE/CCRK supports cell proliferation but has no intrinsic CDK-activating kinase (CAK) activity. Lara Wohlbold, Stéphane Larochelle, Jack C.-F. Liao, Geulah Livshits, Juliet Singer, Kevan M. Shokat and Robert P. Fisher Cell Cycle. 2006 Mar;5(5):546-54.