Post‐initiation roles for the sigma subunit of bacterial RNA polymerase

Promoter recognition in bacteria depends on the σ subunit of RNA polymerase. However, σ can also function during the elongation phase of transcription by recognizing promoter‐like DNA sequence elements in the initial transcribed region that induce early elongation pausing (Roberts et al ., CSH Symp Quant Biol 63: 319–325; 1998). In previous work, we demonstrated that such promoter‐like pause‐inducing elements function to inhibit σ 70 loss during the earliest stage of elongation, increasing the σ 70 content of elongation complexes throughout the transcription unit. This effect of a σ 70 ‐dependent early elongation pause element can be detected as enhanced pausing at downstream locations. Current efforts are directed at investigating the implications of these findings for the control of transcription elongation. We are also investigating the possibility that σ 70 can extend its reach by gaining access to elongation complexes on transcription units that are controlled by non σ 70 ‐dependent promoters.