Autogenous regulation of the EcoRII methylase gene at the transcriptional level: effect of 5-azacytidine.

AUTOR(ES)

Som, S

RESUMO

mRNA of the EcoRII methylase (M.EcoRII), a type II modification enzyme, was induced when Escherichia coli carrying a cloned M.EcoRII gene was exposed to the bacteriocidal drug 5-azacytidine. Induction occurred only when transcription was initiated from its own promoter. When the 5' promoter sequences were deleted or replaced with the lac promoter sequences, no induction occurred. The induction was independent of the template DNA level, but the presence of an intact M.EcoRII protein was a requirement. The drug is incorporated into DNA which then inhibits M.EcoRII by binding tightly to the enzyme. A deletion within the M.EcoRII coding region caused a marked increase in the basal level of mRNA transcribed from the M.EcoRII promoter, but no induction occurred upon 5-azacytidine treatment. The level could be reduced to normal by M.EcoRII in trans. In vitro, the enzyme bound to the sequences upstream of the transcription start sites and inhibited the initiation of transcription. These experiments indicate that expression of the M.EcoRII gene was autogenously regulated at the transcriptional level. Similar regulation is also noted in another DNA (cytosine-5) methylase, M.MspI.

Documentos Relacionados

• Bactericidal effect of 5-azacytidine on Escherichia coli carrying EcoRII restriction-modification enzymes.
• Binding of the EcoRII methylase to azacytosine-containing DNA.
• Induction of EcoRII methyltransferase: evidence for autogenous control.
• Regulation of EcoRII methyltransferase: effect of mutations on gene expression and in vitro binding to the promoter region.
• The core element of the EcoRII methylase as defined by protease digestion and deletion analysis.