CDK-9/cyclin T (P-TEFb) is required in two postinitiation pathways for transcription in the C. elegans embryo

Eun Yong Shim, Amy K. Walker, Yang Shi, T. Keith Blackwell

Research output: Contribution to journalArticlepeer-review

164 Scopus citations


The metazoan transcription elongation factor P-TEFb (CDK-9/cyclin T) is essential for HIV transcription, and is recruited by some cellular activators. P-TEFb promotes elongation in vitro by overcoming pausing that requires the SPT-4/SPT-5 complex, but considerable evidence indicates that SPT-4/SPT-5 facilitates elongation in vivo. Here we used RNA interference to investigate P-TEFb functions in vivo, in the Caenorhabditis elegans embryo. We found that P-TEFb is broadly essential for expression of early embryonic genes. P-TEFb is required for phosphorylation of Ser 2 of the RNA Polymerase II C-terminal domain (CTD) repeat, but not for most CTD Ser 5 phosphorylation, supporting the model that P-TEFb phosphorylates CTD Ser 2 during elongation. Remarkably, although heat shock genes are cdk-9-dependent, they can be activated when spt-4 and spt-5 expression is inhibited along with cdk-9. This observation suggests that SPT-4/SPT-5 has an inhibitory function in vivo, and that mutually opposing influences of P-TEFb and SPT-4/SPT-5 may combine to facilitate elongation, or insure fidelity of mRNA production. Other genes are not expressed when cdk-9, spt-4, and spt-5 are inhibited simultaneously, suggesting that these genes require P-TEFb in an additional mechanism, and that they and heat shock genes are regulated through different P-TEFb-dependent elongation pathways.

Original languageEnglish (US)
Pages (from-to)2135-2146
Number of pages12
JournalGenes and Development
Issue number16
StatePublished - Aug 15 2002
Externally publishedYes


  • C. elegans
  • CDK9
  • DSIF
  • P-TEFb
  • SPT5
  • Transcription

ASJC Scopus subject areas

  • Genetics
  • Developmental Biology


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