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


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.



Exonuclease Activity, Structure and Structure/Function, Alignments

One line summary:

Demostration of the presence of a 3´-5´ exonuclease activity in Bacillus subtilis DNA polymerase X


new topics/pols set partial results complete validated


Polymerase Reference Property Result Context
Bsu Pol X Baños B2008 3-5' Exonuclease (proofreading) Yes
Bsu Pol X Baños B2008 5-3' Exonuclease Unspecified

Entry validated by:

Log in to edit reference All References

Using Polbase tables:


Tables may be sorted by clicking on any of the column titles. A second click reverses the sort order. <Ctrl> + click on the column titles to sort by more than one column (e.g. family then name).


It is also possible to filter the table by typing into the search box above the table. This will instantly hide lines from the table that do not contain your search text.