Expanded Substrate Scope of DNA Polymerase ? and DNA Polymerase ?: Lyase Activity on 5'-Overhangs and Clustered Lesions.

ABSTRACT: DNA polymerase ? (Pol ?) is a multifunctional enzyme with double-strand break (DSB) repair, translesion synthesis, and lyase activities. Pol ? lyase activity on ternary substrates containing a 5'-dRP that are produced during base excision repair of abasic sites (AP) is weak compared to that of DNA polymerase ? (Pol ?), a polymerase integrally involved in base excision repair. This led us to explore whether Pol ? utilizes its lyase activity to remove 5'-dRP and incise abasic sites from alternative substrates that might be produced during DNA damage and repair. We found that Pol ? exhibited lyase activity on abasic lesions near DSB termini and on clustered lesions. To calibrate the Pol ? activity, Pol ? reactivity was examined with the same substrates. Pol ? excised 5'-dRP from within a 5'-overhang 80 times faster than did Pol ?. Pol ? and Pol ? also incised AP within clustered lesions but showed opposite preferences with respect to the polarity of the lesions. AP lesions in 5'-overhangs were typically excised by Pol ? 35-50 times faster than those in a duplex substrate but 15-20-fold more slowly than 5'-dRP in a ternary complex. This is the first report of Pol ? exhibiting lyase activity within an unincised strand. These results suggest that bifunctional polymerases may exhibit lyase activity on a greater variety of substrates than previously recognized. A role in DSB repair could potentially be beneficial, while the aberrant activity exhibited on clustered lesions may be deleterious because of their conversion to DSBs.

SUBMITTER: Laverty DJ 

PROVIDER: S-EPMC6200648 | biostudies-literature | 2018 Oct

REPOSITORIES: biostudies-literature