Response of RNA polymerase to ppGpp: requirement for the ω subunit and relief of this requirement by DksA (original) (raw)

  1. Catherine E. Vrentas1,
  2. Tamas Gaal1,
  3. Wilma Ross1,
  4. Richard H. Ebright2, and
  5. Richard L. Gourse1,3
  6. 1Department of Bacteriology, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA; 2Howard Hughes Medical Institute, Waksman Institute, and Department of Chemistry, Rutgers University, Piscataway, New Jersey 08854, USA

Abstract

Previous studies have come to conflicting conclusions about the requirement for the ω subunit of RNA polymerase in bacterial transcription regulation. We demonstrate here that purified RNAP lacking ω does not respond in vitro to the effector of the stringent response, ppGpp. DksA, a transcription factor that works in concert with ppGpp to regulate rRNA expression in vivo and in vitro, fully rescues the ppGpp-unresponsiveness of RNAP lacking ω, likely explaining why strains lacking ω display a stringent response in vivo. These results demonstrate that ω plays a role in RNAP function (in addition to its previously reported role in RNAP assembly) and highlight the importance of inclusion of ω in RNAP purification protocols. Furthermore, these results suggest that either one or both of two short segments in the β′ subunit that physically link ω to the ppGpp-binding region of the enzyme may play crucial roles in ppGpp and DksA function.

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