Related Experiment Videos
Promoter activities in Vibrio cholerae ctx phi prophage
R Fando1, J L Pérez, B L Rodriguez
1Centro Nacional de Investigaciones Científicas, Havana, Cuba.
Infection and Immunity
|April 1, 1997
Summary
A novel cholera toxin (CT) promoter within the CT A-subunit gene (ctxA) drives CTB production, ensuring proper subunit balance. This promoter also influences zonula occludens toxin gene expression.
Area of Science:
- Microbiology
- Molecular Biology
- Bacterial Pathogenesis
Background:
- Cholera toxin (CT) is the primary virulence factor of Vibrio cholerae, responsible for severe diarrheal disease.
- CT is composed of one A subunit and five B subunits (AB5), with precise stoichiometric production crucial for activity.
- The regulation of CT gene expression, particularly the ctxB gene encoding the B subunit, is complex and not fully understood.
Purpose of the Study:
- To identify and characterize novel regulatory elements controlling cholera toxin gene expression.
- To investigate the transcriptional regulation of the ctxB gene and its contribution to subunit stoichiometry.
- To explore promoter activity upstream of other Vibrio cholerae virulence genes, including zonula occludens toxin (Zot) and accessory cholera enterotoxin (Ace).
Main Methods:
- S1 nuclease mapping was employed to precisely map transcription initiation sites.
- Analysis of CT production from various gene constructs, including promoterless vectors.
- In vitro and in vivo assays were used to detect and quantify promoter activity.
Main Results:
- A ctxB-specific promoter was identified within the coding sequence of the ctxA gene.
- Transcription initiation from this promoter was confirmed in wild-type El Tor and classical biotype V. cholerae.
- This ctxB promoter, along with a strong ribosomal binding site, likely ensures the correct 5B:1A subunit ratio for CT.
- Promoter activity was detected upstream of the zonula occludens toxin (zot) gene, suggesting its in vivo regulation.
- No promoter activity was found upstream of the accessory cholera enterotoxin (ace) gene.
Conclusions:
- A novel, intragenic promoter within ctxA plays a critical role in regulating CTB synthesis and achieving proper CT subunit stoichiometry.
- This finding provides new insights into the intricate regulatory mechanisms governing cholera toxin production.
- The identified promoter upstream of the zot gene suggests a potential role for Zot in V. cholerae pathogenesis and fluid accumulation.