Specificity crosstalk among group 1 and group 2 sigma factors in the cyanobacterium Synechococcus sp. PCC7942: in vitro specificity and a phylogenetic analysis

Abstract

SummaryThe chromosome of the cyanobacterium Synechococcus sp. PCC7942 contains at least one group 1 (rpoD1) and three group 2 (rpoD2, rpoD3 and rpoD4) sigma factor genes. In this study, we have analysed the structure of rpoD3 and rpoD4 and have shown that these genes are dispensable for growth at normal physiological conditions. An RNA polymerase core enzyme of the cyanobacterial strain was puri®ed, reconstituted with the recombinant sigma factors (the rpoD1, rpoD3 and rpoD4 gene products), and the resultant holoenzymes were examined in vitro for transcription speci®city. All of the holoenzymes recognized canonical promoters of Escherichia coli as well as cyanobacterial rrnA, cpcB1A1 P1a and rpoD1 promoters, although the three holoenzymes had some preference for speci®c promoters. These results suggest that group 1 as well as group 2 sigma factors of cyanobacteria may direct transcription initiation from the eubacterial consensus-type promoters containing the Pribnow À10 element, and we postulate that speci®city crosstalk is a common characteristic among eubacterial group 1 and group 2 sigma factors. Phylogenetic analyses revealed that most group 2 sigma factors were positioned in one of four distinct clusters. The implication of the phylogenetic tree is also discussed in this paper.

SigC, the Group 2 Sigma Factor of RNA Polymerase, Contributes to the Late-stage Gene Expression and Nitrogen Promoter Recognition in the CyanobacteriumSynechocystissp. Strain PCC 6803

“…The structures of Synechocystis PCC 6803 SigC, Anabaena PCC 7120 SigC, and Synechococcus PCC 7002 SigE are similar in the cyanobacterial group 2 sigma factors. 17,38) In the nitrogen-fixing cyanobacterium PCC 7120, sigC mRNAs are detectable only under nitrogen-limiting conditions. 12) However, the inactivation of sigC indicates that neither gene alone is essential for nitrogen fixation or heterocyst differentiation.…”

“…[12][13][14][15][16][17][18][19][20] However, the functional assignments and roles of relevant sigma factors are still not clear in y To whom correspondence should be addressed. Tel/Fax: +81-29-888-8651; E-mail: asam@mx.ibaraki.ac.jp cyanobacteria.…”

Characterization of Single and Double Inactivation Strains Reveals New Physiological Roles for Group 2 σ Factors in the Cyanobacterium Synechocystis sp. PCC 6803

“…PCC 7002 (Caslake et al, 1997), and Synechococcus sp. PCC 7942 (Goto- Seki et al, 1999) as well as double inactivation strains in Synechocystis (Fig. 2) indicate that these s factors have little or no effect on growth under optimal conditions.…”

Light‐responsive transcriptional regulation of the suf promoters involved in cyanobacterium Synechocystis sp. PCC 6803 Fe–S cluster biogenesis

“…In vitro transcription analysis was carried out as described previously with some modifications [13]. Briefly, holoenzyme was reconstituted by mixing purified RNAP with a threefold molar excess of r A , and incubated for 20 min at 30°C.…”