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Phosphorylation of RIα by Cyclin-Dependent Kinase CDK 2/Cyclin E Modulates the Dissociation of the RIα-RFC40 Complex
Rakhee S. Gupte, Frank Traganos, Zbigniew Darzynkiewicz and Marietta Y.W.T. Lee
volume 5 | issue 6
16 march 2006Pages: 653 - 660
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We have previously demonstrated that the nuclear transport of the second subunit of the Replication Factor C complex, RFC40, by the regulatory subunit, RIα, of PKA is cell cycle specific and impairment in this transport results in G1 arrest. In this study, we have investigated whether the cyclin-dependent kinases play a role in regulating the RIα-RFC40 complex formation. In this context, we have identified RI? as a novel substrate for the G1/S-Cyclin-dependent kinase, CDK2/Cyclin E, and found that RI? is specifically phosphorylated at the serine residue. Treatment of MCF7 cells with a CDK inhibitor, olomoucine, resulted in a significant accumulation in the RI?-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 RIα by CDK2/CyclinE kinase promotes the dissociation of the RI?-RFC40 complex and that once RI? is phosphorylated it cannot complex with RFC40. Inhibition of the serine-threonine phosphatase, PP1, by Calyculin A, significantly reduced the RIα-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 RIα-RFC40 complex and subsequently the association of the RFC40-RFC37 complex.
We now provide open access to journal articles published online for one year or more. This article may be downloaded at the following link:
Download PDF If the document does not open, please right-click on the link (control-click on a Macintosh) and select the option to save the file to disk.