CDK9 has the intrinsic property to shuttle between nucleus and cytoplasm, and enhanced expression of CyclinT1 promotes its nuclear localization

• Published in: Journal of cellular physiology Vol. 192; no. 2; pp. 209 - 215
• Main Authors: Napolitano, Giuliana, Licciardo, Paolo, Carbone, Roberta, Majello, Barbara, Lania, Luigi
• Format: Journal Article
• Language: English
• Published: New York Wiley Subscription Services, Inc., A Wiley Company 01.08.2002
• ISSN: 0021-9541; 1097-4652
• DOI: 10.1002/jcp.10130

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. © 2002 Wiley‐Liss, Inc.