CDK9 has the intrinsic property to shuttle between nucleus and cytoplasm, and enhanced expression of cyclin T1 promotes its nuclear localization.
CDK9 in association with cyclin T constitutes the P-TEFb complex that stimulates transcription elongation of RNAPII transcripts by phosphorylation of the CTD of RNAPII. Here we report subcellular distribution of P-TEFb in terms of localization of CDK9 and cyclin T1. We found that cyclin T1 is exclusively nuclear and it is present in nuclear-speckled structures. CDK9, albeit mainly nuclear, was also visualized in the cytoplasm. We determined that CDK9 is actively exported from the nucleus, and that leptomycin B (LMB), a specific inhibitor of nuclear export, inhibits this process. Interestingly, enforced expression of cyclin T1 enhances nuclear localization of CDK9. These findings reveal a novel control mechanism for the function of the P-TEFb complex.
Department of Genetics, General and Molecular Biology, University of Naples Federico II, Naples, Italy.
Giuliana
G
Napolitano
Paolo
P
Licciardo
Roberta
R
Carbone
Barbara
B
Majello
Luigi
L
Lania
D016475:3T3 Cells / Q000378:metabolism; D021581:Active Transport, Cell Nucleus / Q000502:physiology; D000818:Animals; D019556:COS Cells / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism*; D002522:Chlorocebus aethiops; D056906:Cyclin T; D042863:Cyclin-Dependent Kinase 9; D018844:Cyclin-Dependent Kinases / Q000378:metabolism*; D016213:Cyclins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D003593:Cytoplasm / Q000378:metabolism*; D006367:HeLa Cells / Q000378:metabolism; D006801:Humans; D051379:Mice; D021381:Protein Transport / Q000502:physiology; D013347:Subcellular Fractions / Q000737:chemistry / Q000201:enzymology
C503684:CCNT1 protein, human; C503685:Ccnt1 protein, mouse; D056906:Cyclin T; D016213:Cyclins; C467969:CDK9 protein, human; C467972:Cdk9 protein, mouse; D042863:Cyclin-Dependent Kinase 9; D018844:Cyclin-Dependent Kinases