Phosphorylation of RIα by cyclin-dependent kinase CDK 2/cyclin E modulates the dissociation of the RIα-RFC40 complex
Phosphorylation of RIα by cyclin-dependent kinase CDK 2/cyclin E modulates the dissociation of the RIα-RFC40 complex
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DOI：
10.4161/cc.5.6.2576
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发表时间：
2006-03-16
期刊：
影响因子：
4.3
通讯作者：
Lee, Marietta Y. W. T.
中科院分区：
文献类型：
--
作者：
Gupte, Rakhee S.;Traganos, Frank;Lee, Marietta Y. W. T.
We have previously demonstrated that the nuclear transport of the second subunit of the Replication Factor C complex, RFC40, by the regulatory subunit, Rl alpha, of PKA is cell cycle specific and impairment in this transport results in G(1) arrest. In this study, we have investigated whether the cyclin-dependent kinases play a role in regulating the Rl alpha-RFC40 complex formation. In this context, we have identified Rl alpha as a novel substrate for the G(1)/S-Cyclin-dependent kinase, CDK2/Cyclin E, and found that Rl alpha is specifically phosphorylated at the serine residue. Treatment of MCF7 cells with a CDK inhibitor, olomoucine, resulted in a significant accumulation in the Rl alpha-RFC40 complex by 3.10 +/- 0.08 fold and a parallel decrease in the RFC40-37 complex formation by 73.73 +/- 11.81%. Furthermore, in vitro phosphorylation experiments suggest that, phosphorylation of Rl alpha by CDK2/CyclinE kinase promotes the dissociation of the Rl alpha-RFC40 complex and that once Rl alpha is phosphorylated it cannot complex with RFC40. Inhibition of the serine-threonine phosphatase, PP1, by Calyculin A, significantly reduced the Rl alpha-RFC40 complex formation, substantiating the in vitro phosphorylation data. Taken together, these findings suggest that CDK2/Cyclin E may function as downstream modulator that regulates the dissociation of the Rl alpha-RFC40 complex and subsequently the association of the RFC40-RFC37 complex.
