Induction of EcoRII methyltransferase: evidence for autogenous control.
AUTOR(ES)
Friedman, S
RESUMO
The cytosine analog 5-azacytidine kills Escherichia coli cells that carry plasmids expressing EcoRII DNA (cytosine 5)methyltransferase under control of its own promoter. We previously showed that this enzyme binds tightly to azacytidine-containing DNA in vitro and proposed that such binding is lethal in vivo. In support of this proposal, we now show that the enzyme sediments with the nucleoid of azacytidine-treated cells. Azacytidine treatment led to an increase in the amount of enzyme, and this increase required sequences in the ecoRIIM promoter region. Enzyme inducibility correlated with drug sensitivity: plasmids carrying the methyltransferase gene but lacking the wild-type promoter did not confer sensitivity. These results suggested that the ecoRIIM gene was under autogenous control. Transcriptional ecoRIIM'-lacZ fusions in E. coli were, therefore, constructed. They showed that expression from the ecoRIIM promoter was inhibited when EcoRII DNA (cytosine-5)methyltransferase was introduced into the cell in trans and inhibition was reversed by treating the cells with azacytidine. These results provide evidence that the expression of the ecoRIIM gene is under autogenous regulation and that cell death induced by azacytidine is due, in part, to the disruption of autoregulation.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=206726Documentos Relacionados
- Regulation of EcoRII methyltransferase: effect of mutations on gene expression and in vitro binding to the promoter region.
- Autogenous regulation of the EcoRII methylase gene at the transcriptional level: effect of 5-azacytidine.
- Binding of the EcoRII methyltransferase to 5-fluorocytosine-containing DNA. Isolation of a bound peptide.
- Binding of the EcoRII methylase to azacytosine-containing DNA.
- EcoRII can be activated to cleave refractory DNA recognition sites.