Elucidating the correlation between the number of TTTTGAT heptamer repeats and cholera toxin promoter activity in Vibrio cholerae O1 pandemic strains

Arindam Naha, Jeffrey H. Withey, Piyali Mukherjee, Rudra Narayan Saha, Prosenjit Samanta, Amit Ghosh, Shin Ichi Miyoshi, Shanta Dutta, Asish K. Mukhopadhyay

Research output: Contribution to journalArticlepeer-review

Abstract

A complex virulence-regulatory cascade controls expression of the cholera toxin genes (ctxAB) in Vibrio cholerae, which eventually leads to the production and secretion of choleragen (CT), responsible for rice watery diarrhoea in infected individuals. The cholera toxin promoter (PctxAB) contains a series of heptad repeats (5′-TTTTGAT-3′), which has previously been shown to play a crucial role in transcriptional regulation of ctxAB by recruiting the transcriptional activators ToxT, ToxR and the nucleoid-associated protein H-NS along the ctx promoter. The number of these repeats differs not only between the two biotypes of V. cholerae O1 strains, but also among the strains belonging to the same biotype. In this study, we examined if regulation of PctxAB is influenced in any way by the number of these repeats. Based on our observations, we posit that ctx activation indeed depends on the number of TTTTGAT heptad repeats within PctxAB, and occupation of the distal repeats by H-NS could prevent transcriptional activation of the ctx genes in V. cholerae O1 pandemic isolates. Our results suggest that ToxT-dependent transcriptional activation may not require entire displacement of H-NS and supports a recently described revised model of ToxT and H-NS mediated PctxAB transcriptional regulation.

Original languageEnglish
Article numberfnac041
JournalFEMS Microbiology Letters
Volume369
Issue number1
DOIs
Publication statusPublished - 2022
Externally publishedYes

Keywords

  • cholera
  • cholera toxin
  • heptad repeat
  • promoter
  • Vibrio cholerae
  • virulence

ASJC Scopus subject areas

  • Microbiology
  • Molecular Biology
  • Genetics

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