Strand displacement synthesis by yeast DNA polymerase ?.

ABSTRACT: DNA polymerase ? (Pol ?) is a replicative DNA polymerase with an associated 3'-5' exonuclease activity. Here, we explored the capacity of Pol ? to perform strand displacement synthesis, a process that influences many DNA transactions in vivo We found that Pol ? is unable to carry out extended strand displacement synthesis unless its 3'-5' exonuclease activity is removed. However, the wild-type Pol ? holoenzyme efficiently displaced one nucleotide when encountering double-stranded DNA after filling a gap or nicked DNA. A flap, mimicking a D-loop or a hairpin structure, on the 5' end of the blocking primer inhibited Pol ? from synthesizing DNA up to the fork junction. This inhibition was observed for Pol ? but not with Pol ?, RB69 gp43 or Pol ?. Neither was Pol ? able to extend a D-loop in reconstitution experiments. Finally, we show that the observed strand displacement synthesis by exonuclease-deficient Pol ? is distributive. Our results suggest that Pol ? is unable to extend the invading strand in D-loops during homologous recombination or to add more than two nucleotides during long-patch base excision repair. Our results support the hypothesis that Pol ? participates in short-patch base excision repair and ribonucleotide excision repair.

SUBMITTER: Ganai RA 

PROVIDER: S-EPMC5041465 | biostudies-literature | 2016 Sep

REPOSITORIES: biostudies-literature