1. Serotype-shifting gene rfbT is a direct transcriptional target of cAMP receptor protein (CRP) in V. cholerae O1
- Author
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Shan Lu, Biao Kan, Jing Li, and Weili Liang
- Subjects
0301 basic medicine ,Cyclic AMP Receptor Protein ,Transcription, Genetic ,Biophysics ,Serogroup ,Biochemistry ,03 medical and health sciences ,0302 clinical medicine ,Bacterial Proteins ,Cholera ,Transcription (biology) ,Cyclic AMP ,Transcriptional regulation ,Electrophoretic mobility shift assay ,Binding site ,Promoter Regions, Genetic ,Vibrio cholerae ,Molecular Biology ,Gene ,Binding Sites ,biology ,Wild type ,Promoter ,Gene Expression Regulation, Bacterial ,Cell Biology ,Molecular biology ,030104 developmental biology ,cAMP receptor protein ,030220 oncology & carcinogenesis ,biology.protein - Abstract
Ogawa and Inaba are two main serotypes of O1 V. cholerae and alternate among cholera epidemics. The rfbT gene encodes a methyltransferase and is required for Ogawa serotype. The Inaba serotype is the consequence of genetic alterations in rfbT gene which results in loss-of-function enzyme product. However, the expression and regulation of rfbT has not been understood yet. Here we demonstrated that a global regulator, cAMP receptor protein (CRP), positively regulates rfbT transcription through a non-canonical CRP binding site (CBS) in its promoter region. This finding is supported by the analyses of rfbT mRNA abundance, rfbT–lacZ fusions and electrophoretic mobility shift assay (EMSA). The analyses of rfbT mRNA level in wild type (WT), Δcrp, and lower or higher level of cAMP backgrounds revealed that CRP is required for rfbT expression in response to intracellular cAMP level. Subsequent rfbT–lacZ fusions and EMSA collectively displayed that cAMP-CRP complex transcriptionally activates rfbT through directly binding to CBS in rfbT promoter region. Consistently, serological microagglutination test showed that crp deletion resulted in at least 4-fold decrease in titer of Ogawa serum compared to its WT. These results expanded our knowledge of understanding the genetic determinants and probable regulatory mechanism of V. cholerae O1 serotype shift between Ogawa and Inaba.
- Published
- 2019