The bacteriophage T4 AsiA protein contacts the β-flap domain of RNA polymerase

Andy H. Yuan, Bryce E. Nickels, Ann Hochschild

Research output: Contribution to journalArticlepeer-review

17 Scopus citations


To initiate transcription from specific promoters, the bacterial RNA polymerase (RNAP) core enzyme must associate with the initiation factor ir, which contains determinants that allow sequence-specific interactions with promoter DNA. Most bacteria contain several σ factors, each of which directs recognition of a distinct set of promoters. A large and diverse family of proteins known as "anti-σ factors" regulates promoter utilization by targeting specific σ factors. The founding member of this family is the AsiA protein of bacteriophage T4. AsiA specifically targets the primary σ factor in Escherichia coli, σ 70, and inhibits transcription from the major class of σ 70-dependent promoters. AsiA-dependent transcription inhibition has been attributed to a well-documented interaction between AsiA and conserved region 4 of σ 70. Here, we establish that efficient AsiA-dependent transcription inhibition also requires direct protein-protein contact between AsiA and the RNAP core. In particular, we demonstrate that AsiA contacts the flap domain of the RNAP β-subunit (the β-flap). Our findings support the emerging view that the β-f lap is a target site for regulatory proteins that affect RNAP function during all stages of the transcription cycle.

Original languageEnglish (US)
Pages (from-to)6597-6602
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number16
StatePublished - Apr 21 2009

All Science Journal Classification (ASJC) codes

  • General


  • Anti-σ factor
  • Transcription initiation
  • Transcription regulation


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