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DNA polymerase X from Deinococcus radiodurans possesses a structure-modulated 3'-->5' exonuclease activity involved in radioresistance.


Blasius, M; Shevelev, I V; Jolivet, E; Sommer, Suzanne; Hübscher, U (2006). DNA polymerase X from Deinococcus radiodurans possesses a structure-modulated 3'-->5' exonuclease activity involved in radioresistance. Molecular Microbiology, 60(1):165-176.

Abstract

Recently a family X DNA polymerase (PolXDr) was identified in the radioresistant bacterium Deinococcus radiodurans. Knockout cells show a delay in double-strand break repair (DSBR) and an increased sensitivity to gamma-irradiation. Here we show that PolXDr possesses 3'-->5' exonuclease activity that stops cutting close to a loop. PolXDr consists of a DNA polymerase X domain (PolXc) and a Polymerase and Histidinol Phosphatase (PHP) domain. Deletion of the PHP domain abolishes only the structure-modulated but not the canonical 3'-->5' exonuclease activity. Thus, the exonuclease resides in the PolXc domain, but the structure-specificity requires additionally the PHP domain. Mutation of two conserved glycines in the PolXc domain leads to a specific loss of the structure-modulated exonuclease activity but not the exonuclease activity in general. The PHP domain itself does not show any activity. PolXDr is the first family X DNA polymerase that harbours an exonuclease activity. The wild-type protein, the glycine mutant and the two domains were expressed separately in DeltapolXDr cells. The wild-type protein could restore the radiation resistance, whereas intriguingly the mutant proteins showed a significant negative effect on survival of gamma-irradiated cells. Taken together our in vivo results suggest that both PolXDr domains play important roles in DSBR in D. radiodurans.

Abstract

Recently a family X DNA polymerase (PolXDr) was identified in the radioresistant bacterium Deinococcus radiodurans. Knockout cells show a delay in double-strand break repair (DSBR) and an increased sensitivity to gamma-irradiation. Here we show that PolXDr possesses 3'-->5' exonuclease activity that stops cutting close to a loop. PolXDr consists of a DNA polymerase X domain (PolXc) and a Polymerase and Histidinol Phosphatase (PHP) domain. Deletion of the PHP domain abolishes only the structure-modulated but not the canonical 3'-->5' exonuclease activity. Thus, the exonuclease resides in the PolXc domain, but the structure-specificity requires additionally the PHP domain. Mutation of two conserved glycines in the PolXc domain leads to a specific loss of the structure-modulated exonuclease activity but not the exonuclease activity in general. The PHP domain itself does not show any activity. PolXDr is the first family X DNA polymerase that harbours an exonuclease activity. The wild-type protein, the glycine mutant and the two domains were expressed separately in DeltapolXDr cells. The wild-type protein could restore the radiation resistance, whereas intriguingly the mutant proteins showed a significant negative effect on survival of gamma-irradiated cells. Taken together our in vivo results suggest that both PolXDr domains play important roles in DSBR in D. radiodurans.

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Item Type:Journal Article, refereed
Communities & Collections:05 Vetsuisse Faculty > Department of Molecular Mechanisms of Disease
07 Faculty of Science > Department of Molecular Mechanisms of Disease
Dewey Decimal Classification:570 Life sciences; biology
Language:English
Date:1 April 2006
Deposited On:11 Feb 2008 12:18
Last Modified:19 Feb 2018 06:41
Publisher:Wiley-Blackwell
ISSN:0950-382X
OA Status:Closed
Publisher DOI:https://doi.org/10.1111/j.1365-2958.2006.05077.x
PubMed ID:16556228

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