Gene-specific requirement for P-TEFb activity and RNA polymerase II phosphorylation within the p53 transcriptional program

Nathan P. Gomes, Glen Bjerke, Briardo Llorente, Stephanie A. Szostek, Beverly M. Emerson*, Joaquin M. Espinosa

*Corresponding author for this work

Research output: Contribution to journalArticle

201 Citations (Scopus)

Abstract

Activation of the p53 pathway mediates cellular responses to diverse forms of stress. Here we report that the p53 target gene p21CIP1 is regulated by stress at post-initiation steps through conversion of paused RNA polymerase II (RNAP II) into an elongating form. High-resolution chromatin immunoprecipitation assays (ChIP) demonstrate that p53-dependent activation of p21CIP1 transcription after DNA damage occurs concomitantly with changes in RNAP II phosphorylation status and recruitment of the elongation factors DSIF (DRB Sensitivity-Inducing Factor), P-TEFb (Positive Transcription Elongation Factor b), TFIIH, TFIIF, and FACT (Facilitates Chromatin Transcription) to distinct regions of the p21CIP1 locus. Paradoxically, pharmacological inhibition of P-TEFb leads to global inhibition of mRNA synthesis but activation of the p53 pathway through p53 accumulation, expression of specific p53 target genes, and p53-dependent apoptosis. ChIP analyses of p21CIP1 activation in the absence of functional P-TEFb reveals the existence of two distinct kinases that phosphorylate Ser5 of the RNAP II C-terminal domain (CTD). Importantly, CTD phosphorylation at Ser2 is not required for p21CIP1 transcription, mRNA cleavage, or polyadenylation. Furthermore, recruitment of FACT requires CTD kinases, yet FACT is dispensable for p21CIP1 expression. Thus, select genes within the p53 pathway bypass the requirement for P-TEFb and RNAP II phosphorylation to trigger a cellular response to inhibition of global mRNA synthesis.

Original languageEnglish
Pages (from-to)601-612
Number of pages12
JournalGenes and Development
Volume20
Issue number5
DOIs
Publication statusPublished - 1 Mar 2006
Externally publishedYes

Keywords

  • Apoptosis
  • P-TEFb
  • p21 gene
  • p53 tumor suppressor protein
  • RNA polymerase II
  • Transcription elongation

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