Antitermination by Bacteriophage Q Protein

The antitermination regulators of bacteriophage λ, proteins encoded by its genes Q and N, provided the first examples of transcription factors that modify the elongationbehavior of RNA polymerase. The category now includesthe NusA, NusG, and Gre proteins in bacteria, as well asRNA polymerase II (pol II) factors such as Tat, elongin,SII, and pTEF. Transcription antitermination was recognized originally through biochemical identification ofbacteriophage λ terminators that require the bacterial termination factor Rho, along with genetic evidence thatregulated expression downstream from the terminatorsderives from promoters located upstream (Roberts 1969).The existence of pol II elongation regulators, includingthe likely function of carboxy-terminal domain (CTD)phosphorylation in elongation, indicates the generality ofsuch modification...