Somatic hypermutation at A/T-rich oligonucleotide substrates shows different strand polarities in Ung-deficient or -proficient backgrounds.

ABSTRACT: A/T mutations at immunoglobulin loci are introduced by DNA polymerase η (Polη) during an Msh2/6-dependent repair process which results in A's being mutated 2-fold more often than T's. This patch synthesis is initiated by a DNA incision event whose origin is still obscure. We report here the analysis of A/T oligonucleotide mutation substrates inserted at the heavy chain locus, including or not including internal C's or G's. Surprisingly, the template composed of only A's and T's was highly mutated over its entire 90-bp length, with a 2-fold decrease in mutation from the 5' to the 3' end and a constant A/T ratio of 4. These results imply that Polη synthesis was initiated from a break in the 5'-flanking region of the substrate and proceeded over its entire length. The A/T bias was strikingly

SUBMITTER: Zivojnovic M 

PROVIDER: S-EPMC4054293 | biostudies-literature | 2014 Jun

REPOSITORIES: biostudies-literature