Cyclin-dependent kinases (CDKs) are key regulators of the cell cycle and RNA polymerase II mediated transcription. Several pharmacological CDK inhibitors are currently in clinical trials as potential cancer therapeutics and some of them also exhibit antiviral effects. Olomoucine II and roscovitine, purine-based inhibitors of CDKs, were described as effective antiviral agents that inhibit replication of a broad range of wild type human viruses. Olomoucine II and roscovitine show high selectivity for CDK7 and CDK9, with important functions in the regulation of RNA polymerase II transcription. RNA polymerase II is necessary for viral transcription and following replication in cells. We analyzed the effect of inhibition of CDKs by olomoucine II on gene expression from viral promoters and compared its effect to widely-used roscovitine. We found that both roscovitine and olomoucine II blocked the phosphorylation of RNA polymerase II C-terminal domain. However the repression of genes regulated by viral promoters was strongly dependent on gene localization. Both roscovitine and olomoucine II inhibited expression only when the viral promoter was not integrated into chromosomal DNA. In contrast, treatment of cells with genome-integrated viral promoters increased their expression even though there was decreased phosphorylation of the C-terminal domain of RNA polymerase II. To define the mechanism responsible for decreased gene expression after pharmacological CDK inhibitor treatment, the level of mRNA transcription from extrachromosomal DNA was determined. Interestingly, our results showed that inhibition of RNA polymerase II C-terminal domain phosphorylation increased the number of transcribed mRNAs. However, some of these mRNAs were truncated and lacked polyadenylation, which resulted in decreased translation. These results suggest that phosphorylation of RNA polymerase II C-terminal domain is critical for linking transcription and posttrancriptional processing of mRNA expressed from extrachromosomal DNA.

• MeSH
• Cell Line MeSH
• Cell Cycle drug effects   MeSH
• Chlorocebus aethiops MeSH
• Cyclin-Dependent Kinases antagonists & inhibitors   MeSH
• DNA, Viral MeSH
• Phosphorylation drug effects   MeSH
• Protein Kinase Inhibitors pharmacology   MeSH
• Kidney drug effects   metabolism   MeSH
• Humans MeSH
• RNA Processing, Post-Transcriptional drug effects   MeSH
• Promoter Regions, Genetic drug effects   MeSH
• Purines pharmacology   MeSH
• RNA Polymerase II genetics   metabolism   MeSH
• Roscovitine MeSH
• Animals MeSH
• Check Tag
• Humans MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Cyclin-Dependent Kinases MeSH
• DNA, Viral MeSH
• Protein Kinase Inhibitors MeSH
• olomoucine II MeSH Browser
• Purines MeSH
• RNA Polymerase II MeSH
• Roscovitine MeSH

Cyclin-dependent kinase inhibitors (CDKi) have high potential applicability in anticancer therapy, but various aspects of their pharmacokinetics, especially their interactions with drug efflux transporters, have not yet been evaluated in detail. Thus, we investigated interactions of five CDKi (purvalanol A, olomoucine II, roscovitine, flavopiridol and SNS-032) with the ABCB1 transporter. Four of the compounds inhibited efflux of two ABCB1 substrates, Hoechst 33342 and daunorubicin, in MDCKII-ABCB1 cells: Olomoucine II most strongly, followed by roscovitine, purvalanol A, and flavopiridol. SNS-032 inhibited ABCB1-mediated efflux of Hoechst 33342 but not daunorubicin. In addition, purvalanol A, SNS-032 and flavopiridol lowered the stimulated ATPase activity in ABCB1 membrane preparations, while olomoucine II and roscovitine not only inhibited the stimulated ATPase but also significantly activated the basal ABCB1 ATPase, suggesting that these two CDKi are ABCB1 substrates. We further revealed that the strongest ABCB1 inhibitors (purvalanol A, olomoucine II and roscovitine) synergistically potentiate the antiproliferative effect of daunorubicin, a commonly used anticancer drug and ABCB1 substrate, in MDCKII-ABCB1 cells as well as in human carcinoma HCT-8 and HepG2 cells. We suggest that this pronounced synergism is at least partly caused by (i) CDKi-mediated inhibition of ABCB1 transporter leading to increased intracellular retention of daunorubicin and (ii) native cytotoxic activity of the CDKi. Our results indicate that co-administration of the tested CDKi with anticancer drugs that are ABCB1 substrates may allow significant dose reduction in the treatment of ABCB1-expressing tumors.

• MeSH
• Adenosine Triphosphatases metabolism   MeSH
• Cell Membrane drug effects   metabolism   MeSH
• Cell Line MeSH
• Cyclin-Dependent Kinases antagonists & inhibitors   MeSH
• Daunorubicin pharmacology   MeSH
• Protein Kinase Inhibitors pharmacology   MeSH
• Humans MeSH
• RNA, Messenger genetics   metabolism   MeSH
• ATP Binding Cassette Transporter, Subfamily B antagonists & inhibitors   genetics   MeSH
• Cell Proliferation drug effects   MeSH
• Antineoplastic Agents pharmacology   MeSH
• Purines pharmacology   MeSH
• Gene Expression Regulation drug effects   MeSH
• Roscovitine MeSH
• Drug Synergism MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• 6-((3-chloro)anilino)-2-(isopropyl-2-hydroxyethylamino)-9-isopropylpurine MeSH Browser
• ABCB1 protein, human MeSH Browser
• Adenosine Triphosphatases MeSH
• Cyclin-Dependent Kinases MeSH
• Daunorubicin MeSH
• Protein Kinase Inhibitors MeSH
• RNA, Messenger MeSH
• olomoucine II MeSH Browser
• ATP Binding Cassette Transporter, Subfamily B MeSH
• Antineoplastic Agents MeSH
• Purines MeSH
• Roscovitine MeSH