Transcription in Bacteria: Bacteria use a variety of mechanisms to direct RNA polymerase to specific promoters in order to activate transcription in response to growth signals or environmental cues. Activation can be due to factors that interact at specific promoters, thereby increasing transcription directed by these promoters. We examine the range of architectures found at activator-dependent promoters and outline the mechanisms by which input from different factors is integrated. Alternatively, activation can be due to factors that interact with RNA polymerase and change its preferences for target promoters. We summarize the different mechanistic options for activation that are focused directly on RNA polymerase.

Factor Responsible for Transcription in Bacteria

A sigma factor is a protein needed only for initiation of RNA synthesis in bacteria. Sigma factors provide promoter recognition specificity to the RNA polymerase (RNAP) and contribute to DNA strand separation; they then dissociate from RNA polymerase core enzyme following transcription initiation. The mechanism is RNA polymerase core associates with the sigma factor to form RNA polymerase holoenzyme. Sigma factor reduces the affinity of RNA polymerase for nonspecific DNA while increasing specificity for promoters, allowing transcription to initiate at correct sites.

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By Team Learning Mantras