The ρ Factor: Termination and Anti-termination in Lambda (original) (raw)

  1. Jeffrey W. Roberts
  2. The Biological Laboratories, Harvard University, Cambridge, Massachusetts

Excerpt

The ρ factor is a protein isolated and purified from E. coli which causes the termination of in vitro RNA synthesis at distinct sites on several bacteriophage DNA templates, producing RNA molecules which are probably identical to natural messenger RNA (mRNA) (Roberts, 1969a). Although synthesis of an RNA chain by RNA polymerase does eventually stop in vitro in the absence of ρ factor, there is clear evidence that with several DNA templates the enzyme without ρ factor passes normal termination sites and stops only after transcribing forbidden regions (Roberts, 1969a; Goff and Minkley, 1970; Travers, 1970). The product synthesized from DNA of phages λ, T4, and T7 in the presence of ρ factor, in contrast, corresponds to the natural mRNA both in the region of the genome copied and in the size of the RNA. In addition to terminating synthesis of RNA molecules, the ρ factor releases them from the...