DNA polymerase I acts in translesion synthesis mediated by the Y-polymerases in Bacillus subtilis

Mol Microbiol. 2005 Aug;57(3):678-90. doi: 10.1111/j.1365-2958.2005.04725.x.


Translesion synthesis (TLS) across damaged DNA bases is most often carried out by the ubiquitous error-prone DNA polymerases of the Y-family. Bacillus subtilis encodes two Y-polymerases, Pol Y1 and Pol Y2, that mediate TLS resulting in spontaneous and ultraviolet light (UV)-induced mutagenesis respectively. Here we show that TLS is a bipartite dual polymerase process in B. subtilis, involving not only the Y-polymerases but also the A-family polymerase, DNA polymerase I (Pol I). Both the spontaneous and the UV-induced mutagenesis are abolished in Pol I mutants affected solely in the polymerase catalytic site. Physical interactions between Pol I and either of the Pol Y polymerases, as well as formation of a ternary complex between Pol Y1, Pol I and the beta-clamp, were detected by yeast two- and three-hybrid assays, supporting the model of a functional coupling between the A- and Y-family polymerases in TLS. We suggest that the Pol Y carries the synthesis across the lesion, and Pol I takes over to extend the synthesis until the functional replisome resumes replication. This key role of Pol I in TLS uncovers a new function of the A-family DNA polymerases.

MeSH terms

  • Bacillus subtilis / enzymology*
  • Bacillus subtilis / genetics
  • Bacillus subtilis / radiation effects
  • DNA Damage*
  • DNA Polymerase I / metabolism*
  • DNA Repair*
  • DNA Replication
  • DNA, Bacterial / biosynthesis*
  • DNA, Bacterial / genetics
  • DNA-Directed DNA Polymerase / classification
  • DNA-Directed DNA Polymerase / metabolism
  • Gene Expression Regulation, Bacterial*
  • Mutagenesis
  • Two-Hybrid System Techniques
  • Ultraviolet Rays


  • DNA, Bacterial
  • DNA Polymerase I
  • DNA-Directed DNA Polymerase