Gre proteins of prokaryotes, and SII proteins of eukaryotes and archaea, are transcription elongation factors that promote an endogenous transcript cleavage activity of RNA polymerases; this process promotes elongation through obstructive regions of DNA, including transcription pauses that act as sites of genetic regulation. We show that a regulatory pause in the early part of the late gene operon of bacteriophage λ is subject to such cleavage and resynthesis. In cells lacking the cleavage factors GreA and GreB, the pause is prolonged, and RNA polymerase occupies a variant position at the pause site. Furthermore, GreA and GreB are required to mediate efficient function of the λ gene Q antiterminator at this site. Thus, cleavage factors are necessary for the natural progression of RNA polymerase in vivo.
Marr, M. T., & Roberts, J. W. (2000). Function of transcription cleavage factors GreA and GreB at a regulatory pause site. Molecular Cell, 6(6), 1275–1285. https://doi.org/10.1016/S1097-2765(00)00126-X