The cyclin-dependent kinase inhibitor roscovitine inhibits RNA synthesis and triggers nuclear accumulation of p53 that is unmodified at Ser15 and Lys382.
Roscovitine has been shown to induce the accumulation of the tumor suppressor p53, to arrest cells in the G(1) and G(2)/M phases of the cell cycle, and to induce apoptosis in human cells. Although these cellular effects of roscovitine are thought to be caused directly by its specific inhibition of cyclin-dependent kinases, other mechanisms may contribute as well. In this study, we investigated whether roscovitine interferes with transcription in human cells. We have previously shown that blockage of transcription is a trigger for the induction of p53 and apoptosis in human fibroblasts. Here we show that mRNA synthesis is suppressed significantly by roscovitine in human cells. Furthermore, our results suggest that the mechanism by which roscovitine inhibits RNA synthesis involves the inhibition of the phosphorylation of the carboxyl-terminal domain of RNA polymerase II. Cells treated with roscovitine at doses that affected transcription were found to accumulate p53 in the nucleus; curiously, however, the nuclear accumulation of p53 was not accompanied by modifications at either the Ser15 or Lys382 sites of p53. We conclude that roscovitine is a potent inhibitor of RNA synthesis and that this inhibition may be responsible for the accumulation of nuclear p53.
Ljungman
M
M
Department of Radiation Oncology, Division of Cancer Biology, University of Michigan Comprehensive Cancer Center, Ann Arbor, Michigan 48109-0936, USA. ljungman@umich.edu
Paulsen
M T
MT
D042846:CDC2-CDC28 Kinases; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism; D002478:Cells, Cultured; D051357:Cyclin-Dependent Kinase 2; D018844:Cyclin-Dependent Kinases / Q000037:antagonists & inhibitors*; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D006801:Humans; D008239:Lysine / Q000378:metabolism; D019384:Nucleic Acid Synthesis Inhibitors / Q000494:pharmacology*; D010766:Phosphorylation / Q000187:drug effects; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors*; D011687:Purines / Q000494:pharmacology*; D012319:RNA Polymerase II / Q000378:metabolism; D012333:RNA, Messenger / Q000187:drug effects / Q000378:metabolism; D000077546:Roscovitine; D012694:Serine / Q000378:metabolism; D016159:Tumor Suppressor Protein p53 / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*
D004791:Enzyme Inhibitors; D019384:Nucleic Acid Synthesis Inhibitors; D011687:Purines; D012333:RNA, Messenger; D016159:Tumor Suppressor Protein p53; D000077546:Roscovitine; D012694:Serine; D017346:Protein Serine-Threonine Kinases; D042846:CDC2-CDC28 Kinases; C495894:CDK2 protein, human; D051357:Cyclin-Dependent Kinase 2; D018844:Cyclin-Dependent Kinases; D012319:RNA Polymerase II; D008239:Lysine