SigC, the group 2 sigma factor of RNA polymerase, contributes to the late-stage gene expression and nitrogen promoter recognition in the cyanobacterium Synechocystis sp. strain PCC 6803.
We examined the role of SigC (Sll0184), a sigma factor of RNA polymerase (RNAP), in a unicellular cyanobacterium, Synechocystis sp. strain PCC 6803. On the inactivation of sigC, which is an Escherichia coli rpoD homolog, cells were viable but had a low survival rate in the stationary phase of growth under normal physiological conditions, indicating that SigC is a group 2 type sigma factor. In analyses of transcript and protein levels using the sigC knockout strain, it was found that expression of glnB, a nitrogen key regulatory gene, is controlled by SigC in the stationary phase. Primer extension revealed that the glnB nitrogen promoter (P2) was specifically recognized by SigC in the stationary phase under conditions of nitrogen starvation. In vitro studies with purified enzymes indicated effective transcription, on supercoiled DNA templates, from P2 by SigC-RNAP with NtcA which is an activator for nitrogen gene transcription. DNase I footprinting also indicated binding and related sites of NtcA and/or RNAP with SigC on the nitrogen promoter. The unique promoter architecture and the mechanism of transcription by RNAP with SigC are also discussed.
Asayama
Munehiko
M
Laboratory of Molecular Genetics, College of Agriculture, Ibaraki University, Inashiki, Japan. asam@mx.ibaraki.ac.jp
Imamura
Sousuke
S
Yoshihara
Satoshi
S
Miyazaki
Ai
A
Yoshida
Naoko
N
Sazuka
Takashi
T
Kaneko
Takakazu
T
Ohara
Osamu
O
Tabata
Satoshi
S
Osanai
Takashi
T
Tanaka
Kan
K
Takahashi
Hideo
H
Shirai
Makoto
M
D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D000458:Cyanobacteria / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism; D018983:DNA Footprinting; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D012321:DNA-Directed RNA Polymerases / Q000378:metabolism; D015870:Gene Expression; D015964:Gene Expression Regulation, Bacterial; D020868:Gene Silencing; D009584:Nitrogen / Q000378:metabolism*; D051922:PII Nitrogen Regulatory Proteins; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding; D040901:Proteomics; D012808:Sigma Factor / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D051922:PII Nitrogen Regulatory Proteins; D012808:Sigma Factor; D014157:Transcription Factors; C081467:sigC protein, Bacteria; C404143:PIID regulatory protein, Bacteria; D012321:DNA-Directed RNA Polymerases; D009584:Nitrogen