Structure and Mechanism in Transcriptional Antitermination by the Bacteriophage λ N Protein

Excerpt

Each of the two early operons and the late operon ofbacteriophage λ contain transcriptional terminators (Fig.1a). As a consequence, the pattern of transcription duringa lytic infection by λ can be viewed as a cascade of transcriptional antitermination mechanisms (for review, seeDas 1993; Greenblatt et al. 1993; Friedman and Court1995; Richardson and Greenblatt 1996). These antitermination mechanisms are "processive" in the sense that theycan influence termination through multiple terminatorsover many kilobases of DNA and many minutes of transcription time. The N gene is the first gene to be transcribed in the leftward early p_L operon and encodes an antitermination factor. Once N protein is made, it modifiesEscherichia coli RNA polymerase transcribing the earlyp_L and p_R operons so that the RNA polymerase transcribes efficiently through all the intrinsic and Rho-dependent terminators of both operons. This leads to the e...