Disease relevance of CycT

• Cdk9 has also been described as the kinase of the TAK complex, which is homologous to the P-TEFb complex and involved in HIV replication [1].

High impact information on CycT

• P-TEFb, a heterodimer of the kinase Cdk9 and cyclin T, was isolated as a factor that stimulates formation of productive transcription elongation complexes in vitro [2].
• Here, we show that P-TEFb is located at >200 distinct sites on Drosophila polytene chromosomes [2].
• Cyclin T2 has two forms (T2a and T2b) because of alternative splicing [3].
• Kc cell nuclear extract depleted of P-TEFb failed to generate long DRB-sensitive transcripts, but this activity was restored upon addition of either native or recombinant P-TEFb [4].
• We now name the large subunit cyclin T and the previously cloned small subunit (Zhu, Y. R., Peery, T., Peng, J. M., Ramanathan, Y., Marshall, N., Marshall, T., Amendt, B., Mathews, M. B., and Price, D. H. (1997) Genes Dev. 11, 2622-2632) cyclin-dependent kinase 9 (CDK9) [4].

Biological context of CycT

• We propose that phosphorylation of the CTD by P-TEFb controls the transition from abortive into productive elongation mode [5].
• CDK9 and cyclin T1 are ubiquitous factors that affects many cellular processes, including cell differentiation and apoptosis [6].
• Regulatory functions of Cdk9 and of cyclin T1 in HIV tat transactivation pathway gene expression [6].
• We knocked down the catalytic subunit of P-TEFb, Cdk9, in Drosophila melanogaster using RNA interference [7].

References