CDK2 is involved in the S-phase lengthening induced by glucocorticoids in normal human lymphocytes

• Published in: European journal of cell biology 2003-05, Vol.82 (5), p.253-261
• Main Authors: Peiretti, Alexandra, Baghdassarian, Nathalie, Gerland, Luc.M., Ffrench, Patrick, Bryon, Paul-André, Magaud, Jean-Pierre, Ffrench, Martine
• Format: Article
• Language: English
• Subjects: Blotting, Northern; CDC2-CDC28 Kinases; CDK2 expression; CDK2-protein complexes; Cell Division - drug effects; Cyclin-Dependent Kinase 2; Cyclin-Dependent Kinases - genetics; Dexamethasone - pharmacology; Gene Expression Regulation - drug effects; glucocorticoid; Glucocorticoids - pharmacology; Humans; Lymphocytes; Lymphocytes - cytology; Lymphocytes - drug effects; Lymphocytes - metabolism; Protein Kinase Inhibitors; Protein Kinases - metabolism; Protein-Serine-Threonine Kinases - genetics; RNA Stability - drug effects; RNA, Messenger - drug effects; RNA, Messenger - genetics; RNA, Messenger - metabolism; S Phase - drug effects; S Phase - genetics; S Phase - physiology; S-phase lengthening
• ISSN: 0171-9335; 1618-1298
• DOI: 10.1078/0171-9335-00298

Involvement of CDK2 in glucocorticoid-mediated S-phase lengthening was analyzed in this work. Dexamethasone (DXM) treatment of PHA-stimulated lymphocytes induced a decrease in CDK2 mRNA expression without any change in mRNA stability. This glucocorticoid-induced decrease in CDK2 mRNA expression could be suppressed by cycloheximide treatment. These results support the hypothesis of an indirect effect of DXM at the transcriptional level. Furthermore, CDK2 protein expression also decreased while the rate of protein synthesis and stability remained unchanged, suggesting a second post-translational level of regulation with the preferential degradation of a CDK2 protein stock fraction. The analysis of co-precipitated proteins showed that glucocorticoids induced modifications of protein complex composition. We found i) a preservation of the linkage capability of CDK2 for cyclin E and A, ii) a relative increase in p27 kip1 linkage, and iii) a decrease in p21 waf1 complexed with CDK2. As a consequence of CDK2 decrease and modifications of protein complex composition, pRb and histone H1 kinase activity of CDK2 was profoundly decreased. All these results pinpoint the role of CDK2 in glucocorticoid-induced S-phase lengthening and the potential activator role of p21 waf1 for CDK2 in human lymphocytes.