Function of transcription cleavage factors GreA and GreB at a regulatory pause site

Gre proteins of prokaryotes, and SII proteins of eukaryotes and archaea, ar e transcription elongation factors that promote an endogenous transcript cl eavage activity of RNA polymerases; this process promotes elongation throug h obstructive regions of DNA, including transcription pauses that act as si tes of genetic regulation. We show that a regulatory pause in the early par t of the late gene operon of bacteriophage lambda is subject to such cleava ge and resynthesis. In cells lacking the cleavage factors GreA and GreB, th e pause is prolonged, and RNA polymerase occupies a variant position at the pause site. Furthermore, GreA and GreB are required to mediate efficient f unction of the lambda gene Q antiterminator at this site. Thus, cleavage fa ctors are necessary for the natural progression of RNA polymerase in vivo.