Early Operon Research Articles

Termination and antitermination in transcription: control of gene expression.

The expression of many, if not all, genes in microbial systems is regulated according to the “operon” model proposed by Jacob and Monod (1). Regulation occurs at the step of initiation of transcription of genes or operons, as was originally outlined by these authors (2). In known cases, this is accomplished by a specific repressor molecule interacting at the operator site to inhibit transcription from the cognate promoter locus (negative control) or a positive factor(s) stimulating transcription (positive control) or both (3,4). The in vitro controlled transcription of certain specific operons has already been demonstrated using purified RNA polymerase holoenzyme. The essential feature of these systems is that transcription is initiated by the correct initiating signals, i.e., promoters. For the lac and gal operons of Escherichia coli, correct initiation depends on the presence of additional positive control elements: cyclic AMP and its recepter protein (CRP) (5–7). In case of the immediate early operons of bacteriophage λ, however, correct transcription occurs just with RNA polymerase holoenzyme alone (8,9). In all of the above three systems, purified lac gal or λ repressor specifically inhibits the transcription of its respective operon (8–11).KeywordsCold Spring HarborInsertion MutationTranscription TerminationPolar MutationTranscription StopThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.