GATC sequences, DNA nicks and the MutH function in Escherichia coli mismatch repair.

摘要: Circular heteroduplex DNAs of bacteriophage phi X174 have been constructed carrying either a G:T (Eam+/Eam3) or G:A (Bam+/Bam16) mismatch and containing two, one no GATC sequences. Mismatches were efficiently repaired in wild-type Escherichia coli transfected with heteroduplexes only when two unmethylated sequences present DNA. The requirements for substrate DNA the E. MutH function repair can be alleviated by presence persistent nick (transfection nicked ligase temperature-sensitive mutant at 40 degrees C). A sequence is as effective stimulating mutL- mutS-dependent distant from mismatch. These observations suggest that protein participates methyl-directed recognizing and/or nicking strands.