Effects of high levels of DNA adenine methylation on methyl-directed mismatch repair in Escherichia coli.

Journal Article (Journal Article)

Two methods were used in an attempt to increase the efficiency and strand selectivity of methyl-directed mismatch repair of bacteriophage lambda heteroduplexes in E. coli. Previous studies of such repair used lambda DNA that was only partially methylated as the source of methylated chains. Also, transfection was carried out in methylating strains. Either of these factors might have been responsible for the incompleteness of the strand selectivity observed previously. In the first approach to increasing strand selectivity, heteroduplexes were transfected into a host deficient in methylation, but no changes in repair frequencies were observed. In the second approach, heteroduplexes were prepared using DNA that had been highly methylated in vitro with purified DNA adenine methylase as the source of methylated chains. In heteroduplexes having a repairable cI/+ mismatch, strand selectivity was indeed enhanced. In heteroduplexes with one chain highly methylated and the complementary chain unmethylated, the frequency of repair on the unmethylated chain increased to nearly 100%. Heteroduplexes with both chains highly methylated were not repaired at a detectable frequency. Thus, chains highly methylated by DNA adenine methylase were refractory to mismatch repair by this system, regardless of the methylation of the complementary chain. These results support the hypothesis that methyl-directed mismatch repair acts to correct errors of replication, thus lowering the mutation rate.

Full Text

Duke Authors

Cited Authors

  • Pukkila, PJ; Peterson, J; Herman, G; Modrich, P; Meselson, M

Published Date

  • August 1983

Published In

Volume / Issue

  • 104 / 4

Start / End Page

  • 571 - 582

PubMed ID

  • 6225697

Pubmed Central ID

  • PMC1202127

International Standard Serial Number (ISSN)

  • 0016-6731

Digital Object Identifier (DOI)

  • 10.1093/genetics/104.4.571


  • eng

Conference Location

  • United States