Effects of base changes at the transcription start site on stringent control of rnpB in Escherichia coli.
The GC-rich discriminator sequence between the -10 region and the transcription start site of the rnpB promoter is responsible for stringent control of M1 RNA synthesis. The rnpB promoter also contains a G nucleotide at the previously identified transcription start site. In this study, we examined by mutagenesis of G to A whether this +1G nucleotide is involved in the stringent response. We found that the change did not alter the stringent response. Since the +1 mutation might alter transcription initiation, we compared the transcription start sites of the wt and mutant promoters by primer extension analysis. Surprisingly, we found that wild type rnpB transcription starts at both the +1G position (70%) and the -1C position (30%), and that the +1A mutation led to transcription initiation exclusively at the -1C position. We also generated two transversion mutations at the -1 position, both of which led to transcription starting exclusively at that position. The -1G mutant promoter gave a stringent signal similar to the wild-type, whereas the -1A mutant generated a significantly less stringent signal. Base on these results, we propose that a short sequence, up to 7 bp downstream of the -10 region, is involved in the stringent response of the rnpB promoter.
Choi
Hyun-Sook
HS
Department of Chemistry and Center for Molecular Design and Synthesis, Korea Advanced Institute of Science and Technology, Daejeon 305-701, Korea.
Park
Jeong Won
JW
Hong
Soon Kang
SK
Lee
Kangseok
K
Lee
Younghoon
Y
D001483:Base Sequence; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D011401:Promoter Regions, Genetic / Q000235:genetics*; D043262:Ribonuclease P / Q000235:genetics*; D024363:Transcription Initiation Site / Q000502:physiology*
D029968:Escherichia coli Proteins; D043262:Ribonuclease P; C470865:ribonuclease P, E coli