Breaks in DNA stimulate Transcription by Core RNA Polymerase

Abstract

RECENTLY Burgess et al.¹ discovered a protein that can bind to E. coli RNA polymerase and greatly stimulate its activity on certain DNA templates. This “sigma” factor, which remains attached to the “core” enzyme through most purifications, has since been shown to act at the level of initiation². The core polymerase alone can transcribe some templates quite well, for instance, calf thymus DNA, while it is virtually inactive on others, such as T-4 DNA. The existence of sigma and the suggestion that other similar factors may be involved in regulation of transcription raise the question whether there is any biological significance to the low level at which the core polymerase can read DNA templates. The experiments described here show that (a) breaks in the DNA template can stimulate RNA synthesis, but that (b) breaks or free ends cannot account for all of the synthesis by core polymerase.