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Nucleic Acids Res. 2008 Oct;36(18):5736-49. doi: 10.1093/nar/gkn526. Epub 2008 Sep 6.

Editing of misaligned 3'-termini by an intrinsic 3'-5' exonuclease activity residing in the PHP domain of a family X DNA polymerase.

Author information

1
Instituto de Biología Molecular Eladio Viñuela (CSIC), Centro de Biología Molecular Severo Ochoa (CSIC-UAM), C/Nicolás Cabrera 1, Cantoblanco, 28049 Madrid, Spain.

Abstract

Bacillus subtilis gene yshC encodes a family X DNA polymerase (PolX(Bs)), whose biochemical features suggest that it plays a role during DNA repair processes. Here, we show that, in addition to the polymerization activity, PolX(Bs) possesses an intrinsic 3'-5' exonuclease activity specialized in resecting unannealed 3'-termini in a gapped DNA substrate. Biochemical analysis of a PolX(Bs) deletion mutant lacking the C-terminal polymerase histidinol phosphatase (PHP) domain, present in most of the bacterial/archaeal PolXs, as well as of this separately expressed protein region, allow us to state that the 3'-5' exonuclease activity of PolX(Bs) resides in its PHP domain. Furthermore, site-directed mutagenesis of PolX(Bs) His339 and His341 residues, evolutionary conserved in the PHP superfamily members, demonstrated that the predicted metal binding site is directly involved in catalysis of the exonucleolytic reaction. The implications of the unannealed 3'-termini resection by the 3'-5' exonuclease activity of PolX(Bs) in the DNA repair context are discussed.

PMID:
18776221
PMCID:
PMC2566882
DOI:
10.1093/nar/gkn526
[Indexed for MEDLINE]
Free PMC Article

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