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

Abstract

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.

Control of expression of LlaI restriction in Lactococcus lactis

“…This suggests that different parameters elicit varying regulatory responses affecting expression of this methylase (Rasmussen et al, 1994). Evidence has been found for feedback regulation of transcription of the EcoRII methylase gene (Som and Friedman, 1993), and regulation of the DpnII methylase by RNA processing has been suggested , implicating at least two possible mechanisms of regulating methylase genes.…”

Diverse Domains of (Cytosine-5)-DNA Methyltransferases: Structural and Functional Characterization

“…Investigation of M.EcoRII catalytically inactive forms shows that the efficiency of the MTase binding to the promoter region does not depend on its ability to methylate substrate. These facts demonstrate that M.EcoRII consists of two domains: a catalytic domain and a domain responsible for the interaction with the promoter region [70].…”

Maintenance Forced by a Restriction-Modification System Can Be Modulated by a Region in Its Modification Enzyme Not Essential for Methyltransferase Activity

“…Because the N terminus is implicated in the regulation of transcription of the EcoRII gene complex (62,63) (open circle; pACYC184 carrying wild-type ecoRIIRM, Cml r ) was grown at 30°C in LB broth without antibiotic selection with aeration. After overnight incubation, the culture was examined for plasmid-carrying cell counts (on LB agar with Cml at 30°C) and viable cell counts (on LB agar without Cml at 30°C).…”

“…The N terminus of M.EcoRII is reported to regulate transcription of the M.EcoRII gene by binding to the promoter (62,63). The predicted helix-turn-helix motif 20 amino acid residues upstream of L80P is likely to be responsible for this regulation (28).…”

“…Furthermore, type II RM systems show some similarity to viruses in their requirements for regulation of gene expression (30,49,60,62,66) in that, when they enter a new host, they have to establish themselves without excessive killing of the host cells. After establishment, type II RM systems, like the other types of postsegregational systems, are expected to tightly regulate their gene expression.…”