Dam‐dependent phase variation of Ag43 in Escherichia coli is altered in a seqA mutant

摘要: In Escherichia coli, phase variation of the outer membrane protein Ag43 encoded by agn43 gene is mediated DNA methylation and global regulator OxyR. Transcription occurs (ON phase) when three Dam target sequences in regulatory region are methylated, which prevents repressor OxyR from binding. Conversely, transcription repressed (OFF) these unmethylated binds. A change expression requires a concomitant state sequences. To gain insight into process inheritance state, protein-DNA interactions at were examined. Binding was sufficient to protect GATC contained within its binding site Dam-dependent vitro, suggesting that no other factors required maintain OFF phase. methylated ON phase, however, must access hemimethylated after replication, not occur. bound DNA, but affinity severalfold lower than for DNA. This presumably contributes maintenance but, same time, may allow infrequent switch Hemimethylated also substrate sequestration SeqA. Thus, SeqA, compete formed replication an cell. isolates with mutant seqA allele, rates altered resulted bias part, this can be attributed observed decrease level mutant.