P-TEFb containing cyclin K and Cdk9 can activate transcription via RNA

Xin Lin, Ran Taube, Koh Fujinaga, B. Matija Peterlin

Research output: Contribution to journalArticlepeer-review

38 Scopus citations


Different positive transcription elongation factor b (P-TEFb) complexes isolated from mammalian cells contain a common catalytic subunit (Cdk9) and the unique regulatory cyclins CycT1, CycT2a, CycT2b, or CycK. The role of CycK as a transcriptional cyclin was demonstrated in this study. First, CycK activated transcription when tethered heterologously to RNA, which required the kinase activity of Cdk9. Although this P-TEFb could phosphorylate the C-terminal domain (CTD) of RNA polymerase II (RNAPII) in vitro, in contrast to CycT1 and CycT2, CycK did not activate transcription when tethered to DNA. Interestingly, when the C termini of CycT1 and CycT2 or only the histidine-rich stretch from positions 481 to 551 in CycT1 were added to CycK, the extended chimeras activated transcription equivalently via DNA. Moreover, these transcriptional effects required the CTD of RNAPII in cells. Thus, CycK functions as P-TEFb only via RNA, which suggests the presence of cellular RNA-bound activators that require CycK for their transcriptional activity.

Original languageEnglish
Pages (from-to)16873-16878
Number of pages6
JournalJournal of Biological Chemistry
Issue number19
StatePublished - 10 May 2002
Externally publishedYes

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology


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