Stringent promoter recognition and autoregulation by the group 3 sigma-factor SigF in the cyanobacterium Synechocystis sp. strain PCC 6803.
The cyanobacteirum Synechocystis sp. strain PCC 6803 possesses nine species of the sigma (sigma)-factor gene for RNA polymerase (RNAP). Here, we identify and characterize the novel-type promoter recognized by a group 3 sigma-factor, SigF. SigF autoregulates its own transcription and recognizes the promoter of pilA1 that acts in pilus formation and motility in PCC 6803. The pilA1 promoter (PpilA1-54) was recognized only by SigF and not by other sigma-factors in PCC 6803. No PpilA1-54 activity was observed in Escherichia coli cells that possess RpoF (sigma(28)) for fragellin and motility. Studies of in vitro transcription for PpilA1-54 identified the region from -39 to -7 including an AG-rich stretch and a core promoter with TAGGC (-32 region) and GGTAA (-12 region) as important for transcription. We also confirmed the unique PpilA1-54 architecture and further identified two novel promoters, recognized by SigF, for genes encoding periplasmic and phytochrome-like phototaxis proteins. These results and a phylogenetic analysis suggest that the PCC 6803 SigF is distinct from the E. coli RpoF or RpoD (sigma(70)) type and constitutes a novel eubacterial group 3 sigma-factor. We discuss a model case of stringent promoter recognition by SigF. Promoter types of PCC 6803 genes are also summarized.
Asayama
Munehiko
M
Laboratory of Molecular Genetics, School of Agriculture, Ibaraki University, 3-21-1 Ami, Inashiki, Ibaraki 300-0393, Japan. asam@mx.ibaraki.ac.jp
Imamura
Sousuke
S
D024506:5' Flanking Region; D001426:Bacterial Proteins / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D004247:DNA / Q000737:chemistry; D012321:DNA-Directed RNA Polymerases / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000378:metabolism; D036781:Fimbriae Proteins / Q000096:biosynthesis / Q000235:genetics*; D006706:Homeostasis; D016296:Mutagenesis; D010802:Phylogeny; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D016415:Sequence Alignment; D012808:Sigma Factor / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D046939:Synechocystis / Q000235:genetics*; D013698:Templates, Genetic; D024363:Transcription Initiation Site; D014158:Transcription, Genetic
D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; C064971:FliA protein, Bacteria; D012808:Sigma Factor; D036781:Fimbriae Proteins; D004247:DNA; D012321:DNA-Directed RNA Polymerases