CDK2 is involved in the S-phase lengthening induced by glucocorticoids in normal human lymphocytes.
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 p27kip1 linkage, and iii) a decrease in p21waf1 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 p21waf1 for CDK2 in human lymphocytes.
Peiretti
Alexandra
A
Laboratoire de Cytologie Analytique, Faculté de Médecine, INSERM U.453, Lyon, France.
Baghdassarian
Nathalie
N
Gerland
Luc M
LM
Ffrench
Patrick
P
Bryon
Paul-André
PA
Magaud
Jean-Pierre
JP
Ffrench
Martine
M
D015152:Blotting, Northern; D042846:CDC2-CDC28 Kinases; D002455:Cell Division / Q000187:drug effects; D051357:Cyclin-Dependent Kinase 2; D018844:Cyclin-Dependent Kinases / Q000235:genetics*; D003907:Dexamethasone / Q000494:pharmacology*; D005786:Gene Expression Regulation / Q000187:drug effects; D005938:Glucocorticoids / Q000494:pharmacology*; D006801:Humans; D008214:Lymphocytes / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D047428:Protein Kinase Inhibitors; D011494:Protein Kinases / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000235:genetics*; D020871:RNA Stability / Q000187:drug effects; D012333:RNA, Messenger / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D016196:S Phase / Q000187:drug effects* / Q000235:genetics / Q000502:physiology
D005938:Glucocorticoids; D047428:Protein Kinase Inhibitors; D012333:RNA, Messenger; D003907:Dexamethasone; D011494:Protein Kinases; C102333:histone H1 kinase; D017346:Protein Serine-Threonine Kinases; D042846:CDC2-CDC28 Kinases; C495894:CDK2 protein, human; D051357:Cyclin-Dependent Kinase 2; D018844:Cyclin-Dependent Kinases