The cyclin-dependent kinase (CDK) family member PNQALRE/CCRK supports cell proliferation but has no intrinsic CDK-activating kinase (CAK) activity Journal Article
| Authors: | Wohlbold, L.; Larochelle, S.; Liao, J. C. F.; Livshits, G.; Singer, J.; Shokat, K. M.; Fisher, R. P. |
| Article Title: | The cyclin-dependent kinase (CDK) family member PNQALRE/CCRK supports cell proliferation but has no intrinsic CDK-activating kinase (CAK) activity |
| Abstract: | The cyclin-dependent kinases (CDKs) that drive the eukaryotic cell cycle must be phosphorylated within the activation segment (T-loop) by a CDK-activating kinase (CAK) to achieve full activity. Although a requirement for CDK-activating phosphorylation is conserved throughout eukaryotic evolution, CAK itself has diverged between metazoans and budding yeast, and fission yeast has two CAKs, raising the possibility that additional mammalian enzymes remain to be identified. We report here the characterization of PNQALRE (also known as CCRK or p42), a member of the mammalian CDK family most similar to the cell-cycle effectors Cdk1 and Cdk2 and to the CAK, Cdk7. Although PNQALRE/CCRK was recently proposed to activate Cdk2, we show that the monomeric protein has no intrinsic CAK activity. Depletion of PNQALRE by >80% due to RNA interference (RNAi) impairs cell proliferation, but fails to arrest the cell cycle at a discrete point. Instead, both the fraction of cells with a sub-G 1 DNA content and cleavage of poly(ADP-ribose) polymerase (PARP) increase. PNQALRE knockdown did not diminish Cdk2 T-loop phosphorylation in vivo or decrease CAK activity of a cell extract. In contrast, depletion of Cdk7 by RNAi causes a proportional decrease in the ability of an extract to activate recombinant Cdk2. Our data do not support the proposed function of PNQALRE/ CCRK in activating CDKs, but instead reinforce the notion of Cdk7 as the major, and to date the only, CAK in mammalian cells. ©2006 Landes Bioscience. |
| Keywords: | controlled study; exons; nonhuman; cell proliferation; animal cell; mouse; mammalia; animals; mice; animal tissue; cell cycle; apoptosis; gene expression profiling; protein depletion; rna interference; in vivo study; enzyme activation; enzyme activity; recombinant enzyme; phosphorylation; animalia; rna; dna; enzyme phosphorylation; amino acid sequence; molecular sequence data; rna, messenger; sequence alignment; eukaryota; mammal; nucleotide sequence; cell cycle arrest; chemical genetics; cell fractionation; saccharomycetales; protein family; cyclin-dependent kinases; cyclin dependent kinase; nicotinamide adenine dinucleotide adenosine diphosphate ribosyltransferase; testis; cell cycle g1 phase; cyclin dependent kinase 7; cyclin dependent kinase activating kinase; metazoa; schizosaccharomyces pombe; rnai; cyclin dependent kinase 2; cyclin-dependent kinase 2; cell extract; cdk7; protein p42; analog-sensitive kinase; cdk-activating kinase (cak); cyclin-dependent kinase (cdk); pnqalre/ccrk |
| Journal Title: | Cell Cycle |
| Volume: | 5 |
| Issue: | 5 |
| ISSN: | 1538-4101 |
| Publisher: | Taylor & Francis Inc. |
| Date Published: | 2006-03-01 |
| Start Page: | 546 |
| End Page: | 554 |
| Language: | English |
| PUBMED: | 16552187 |
| PROVIDER: | scopus |
| DOI/URL: | |
| Notes: | --- - "Cited By (since 1996): 28" - "Export Date: 4 June 2012" - "Molecular Sequence Numbers: GENBANK: AAF89089, AK075325, H17727;" - "Source: Scopus" |
