Inhibitory effect of ochratoxin A on DNMT-mediated flocculation of yeast

Area of Science:

• Toxicology
• Epigenetics
• Molecular Biology

Background:

• The mycotoxin ochratoxin A (OTA) is a known human carcinogen, but its carcinogenic mechanism remains unclear.
• Epigenetic alterations, including DNA methylation, are increasingly recognized as key factors in cancer development.
• DNA methyltransferases (DNMTs) regulate DNA methylation and are involved in epigenetic control.

Purpose of the Study:

• To investigate the effect of OTA on the transcriptional activity of the FLO1 gene, which is regulated by epigenetic mechanisms.
• To explore whether OTA's carcinogenicity is linked to the inhibition of DNMT activity and subsequent epigenetic dysregulation.

Main Methods:

• Utilized a yeast model expressing human DNA methyltransferases (DNMTs) and monitored FLO1 promoter activity via GFP fluorescence.
• Assessed OTA's impact on reporter gene activity with normal and modified FLO1 promoters (reduced CpG motifs).
• Performed in vitro methylation assays to directly measure OTA's effect on bacterial DNMT activity.

Main Results:

• Ochratoxin A (OTA) dose-dependently inhibited FLO1 promoter-driven GFP fluorescence, unlike deoxynivalenol (DON).
• OTA's inhibitory effect was diminished with a modified FLO1 promoter lacking CpG motifs, suggesting methylation involvement.
• OTA reduced yeast flocculation, FLO1 mRNA levels, and the frequency of abnormal nuclei in DNMT-transformed yeast, while inhibiting DNMT activity in vitro.

Conclusions:

• Ochratoxin A (OTA) may exert its carcinogenic effects by inhibiting DNA methyltransferase (DNMT) activity.
• This inhibition of DNMT-mediated epigenetic regulation by OTA could contribute to its carcinogenicity.
• Further research into OTA's epigenetic targets is warranted to fully understand its toxicological profile.