The Functional and Regulatory Roles of Sigma Factors in Transcription

RNA polymerase I activation and hibernation: unique mechanisms for unique genes

“…In bacteria, a holoenzyme was defined to designate the complex between the RNA polymerase core and the σ factor, which is sufficient for promoter binding and DNA melting [31]. In archaea and eukaryotes the situation is more sophisticated because, for promoter-specific transcription, general transcription factors must bind DNA prior to enzyme recruitment.…”

Mutational Analysis of Transcriptional Initiation in Bacteria

“…Although the core RNA polymerase with its five subunits is responsible for the production of RNA during transcription in E. coli and most bacteria, initiation of transcription requires its association with a subunit called the sigma factor (Gross et al, 1998). The primary sigma factor, sigma 70, initiates transcription of genes needed during exponential growth.…”

DNA Binding Specificity of Mu Transcription Factor C and Crystallization of C : DNA Complex

“…There are seven different species of the σ subunit identified in Escherichia coli (E.coli) (Gross et al, 1998;Helmann and Figure 1-1. Domain organization of σ 70 into various conserved regions with their identified functions.…”

“…There are four flexible domains in σ 70 referred to as σ 1.1 , σ 2 , σ 3 and σ 4 (Helmann and Chamberlin, 1988) ( Figure 1-1). Each domain contains one or more highly conserved regions; 1.1 and 1.2, 2.1-2.4, 3.1-3.2 and 4.1-4.2 (Malhotra et al, 1996;Gross, 1998;Borukhov and Severinov, 2002;Campbell et al, 2002;Murakami et al, 2002;Vassylyev et al, 2002;Murakami and Darst, 2003). The σ 70 makes sequence-specific contacts within the -10 hexamer (consensus TATAAT) and -35 hexamer (consensus TTGACA) of the promoter using region 2.4 and region 4.2 only when σ 70 is bound to the core RNAP.…”

“…The hexamers are only contacted by the σ subunit of the RNAP holoenzyme (Thomas et al, 1996;Gross et al, 1998). In some promoters an AT-rich region known as the UP element is present just upstream of the -35 hexamer; and this region contains two distinct subsites (proximal and distal), which are recognized by the α-CTD (Ross et al, 1993;Gaal et al, 1996;Estrem et al, 1998).…”