Stability of Escherichia coli sodA mRNA and identification of the transcriptional start site(s) under different environmental and oxidative stresses.
Manganese-containing superoxide dismutase (MnSOD-sodA) in Escherichia coli (E. coli) is regulated at the transcriptional level as observed in studies using both operon and gene fusions. In this paper we examine the regulation of sodA gene at the level of mRNA. We examine the effects of several aerobic inducing conditions (i.e., nalidixic acid, paraquat, or 2,2'-dipyridyl) on mRNA stability, transcription initiation, and translation. The half-life of sodA mRNA was found to be approximately 3-4 min, showing no differences in mRNA stability between induced and uninduced cells. We also found, by reverse transcriptase, that the second putative promoter is not functional under normal or stress conditions, and the amount of mRNA was found to be proportional to active MnSOD. Thus, these results indicate that under oxidative stress/inducing conditions, the increase in aerobic transcription of sodA occurs from only one transcription start site without affecting the stability of sodA mRNA. In addition, the 1:1 ratio found between increases in sodA mRNA and active MnSOD suggests that no translational regulation occurs aerobically.
Schrum
L W
LW
Department of Microbiology, North Carolina State University, Raleigh 27695-7615.
Hassan
H M
HM
D015082:2,2'-Dipyridyl / Q000494:pharmacology; D001483:Base Sequence; D004355:Drug Stability; D004926:Escherichia coli / Q000235:genetics*; D006207:Half-Life; D008345:Manganese; D008969:Molecular Sequence Data; D009268:Nalidixic Acid / Q000494:pharmacology; D010084:Oxidation-Reduction; D018384:Oxidative Stress; D010269:Paraquat / Q000494:pharmacology; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000378:metabolism*; D017382:Reactive Oxygen Species / Q000494:pharmacology; D013482:Superoxide Dismutase / Q000235:genetics*; D014158:Transcription, Genetic / Q000187:drug effects
D012333:RNA, Messenger; D017382:Reactive Oxygen Species; D009268:Nalidixic Acid; D008345:Manganese; D015082:2,2'-Dipyridyl; D013482:Superoxide Dismutase; D010269:Paraquat