Promoter activities in Corynebacterium glutamicum strains with deletions of genes encoding sigma factors of RNA polymerase suggested that transcription from some promoters is controlled by two sigma factors. To prove that different sigma factors are involved in the recognition of selected Corynebacterium glutamicum promoters, in vitro transcription system was applied. It was found that a typical housekeeping promoter Pper interacts with the alternative sigma factor σ(B) in addition to the primary sigma factor σ(A). On the other way round, the σ(B)-dependent promoter of the pqo gene that is expressed mainly in the stationary growth phase was active also with σ(A). Some promoters of genes involved in stress responses (P1clgR, P2dnaK, and P2dnaJ2) were found to be recognized by two stress-responding sigma factors, σ(H) and σ(E). In vitro transcription system thus proved to be a useful direct technique for demonstrating the overlap of different sigma factors in recognition of individual promoters in C. glutamicum.
3-Nitrobenzanthrone (3-NBA), a suspected human carcinogen occurring in diesel exhaust and air pollution, and its human metabolite 3-aminobenzanthrone (3-ABA) were investigated for their ability to induce biotransformation enzymes in rat liver and the influence of such induction on DNA adduct formation by the compounds. Rats were treated (i.p.) with 0.4, 4, or 40 mg/kg body weight 3-NBA or 3-ABA. When hepatic cytosolic fractions from rats treated with 40 mg/kg body weight 3-NBA or 3-ABA were incubated with 3-NBA, DNA adduct formation, measured by 32P-postlabeling analysis, was 10-fold higher in incubations with cytosols from pretreated rats than with controls. The increase in 3-NBA-derived DNA adduct formation corresponded to a dose-dependent increase in protein levels and enzymatic activity of NAD(P)H:quinone oxidoreductase (NQO1). NQO1 is the major enzyme reducing 3-NBA in human and rat livers. Incubations of 3-ABA with hepatic microsomes of rats treated with 3-NBA or 3-ABA (40 mg/kg body weight) led to as much as a 12-fold increase in 3-ABA-derived DNA adduct formation compared with controls. The observed stimulation of DNA adduct formation by both compounds was attributed to their potential to induce protein expression and enzymatic activity of cytochromes P450 1A1 and/or -1A2 (CYP1A1/2), the major enzymes responsible for 3-ABA activation in human and rat livers. Collectively, these results demonstrate for the first time, to our knowledge, that by inducing hepatic NQO1 and CYP1A1/2, both 3-NBA and 3-ABA increase the enzymatic activation of these two compounds to reactive DNA adduct-forming species, thereby enhancing their own genotoxic potential.
- MeSH
- adukty DNA MeSH
- benz(a)anthraceny farmakologie MeSH
- enzymová indukce MeSH
- financování organizované MeSH
- jaterní mikrozomy enzymologie účinky léků MeSH
- játra enzymologie účinky léků MeSH
- karcinogeny farmakologie MeSH
- králíci MeSH
- krysa rodu rattus MeSH
- látky znečišťující životní prostředí farmakologie MeSH
- lidé MeSH
- messenger RNA analýza MeSH
- NAD(P)H dehydrogenasa (chinon) biosyntéza MeSH
- potkani Wistar MeSH
- systém (enzymů) cytochromů P-450 biosyntéza genetika MeSH
- zvířata MeSH
- Check Tag
- králíci MeSH
- krysa rodu rattus MeSH
- lidé MeSH
- mužské pohlaví MeSH
- zvířata MeSH
- MeSH
- adukty DNA účinky léků MeSH
- benz(a)anthraceny farmakologie MeSH
- exprese genu účinky léků MeSH
- finanční podpora výzkumu jako téma MeSH
- jaterní mikrozomy enzymologie účinky léků MeSH
- lidé MeSH
- mutageny farmakologie MeSH
- systém (enzymů) cytochromů P-450 genetika účinky léků MeSH
- Check Tag
- lidé MeSH
