Premium
DNA mismatch‐repair in Escherichia coli counteracting the hydrolytic deamination of 5‐methyl‐cytosine residues.
Author(s) -
Zell R.,
Fritz H. J.
Publication year - 1987
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1002/j.1460-2075.1987.tb02435.x
Subject(s) - deamination , biology , heteroduplex , cytosine , dna mismatch repair , dna , guanine , escherichia coli , dna repair , biochemistry , dna glycosylase , microbiology and biotechnology , base pair , gene , nucleotide , enzyme
Derivatives of phage M13 were constructed and used for the in vitro preparation of heteroduplex DNA molecules containing base/base mismatches that mimick DNA lesions caused by hydrolytic deamination of 5‐meC residues in Escherichia coli DNA (i.e. they carry a T/G mismatch in the special sequence context provided by the recognition site ‐CCA/TGG‐of the Dcm‐methyltransferase). Upon introduction of these heteroduplex DNAs into CaCl2‐treated E. coli cells, the mismatches are efficiently repaired with high bias in favour of the DNA strand containing the mismatched guanine residue. This special DNA mismatch‐repair operates on fully dam‐methylated DNA and is independent of gene mutH. It thus fulfills the salient requirements of a repair pathway responsible for counteracting the spontaneous hydrolytic deamination of 5‐meC in vivo. The repair efficiency is boosted by a 5‐methyl group present on the cytosine residue at the next‐nearest position to the 5′ side of the mismatched guanine. The repair is severely impaired in host strains carrying a mutation in any of the three loci dcm, mutL and mutS.