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J. Biol. Chem., Vol. 282, Issue 15, 10908-10914, April 13, 2007

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Lesion Bypass Activity of DNA Polymerase A from the Extremely Radioresistant Organism Deinococcus radiodurans^*

From the Chair of Organic Chemistry/Cellular Chemistry, Department of Chemistry, University of Konstanz, 78457 Konstanz, Germany

The bacterium Deinococcus radiodurans survives extremely high exposure to ionizing radiation and extended periods of desiccation. Radiation at the survival doses is known to cause numerous DNA damage, such as hundreds of double strand breaks and single strand breaks, as well as damage of the nucleobases. The mechanisms of D. radiodurans to survive the depicted threats are still only beginning to be understood. DNA polymerase A (PolA) has been shown to be crucially involved in irradiation resistance mechanisms of D. radiodurans. We expressed and characterized the DNA polymerase domain of PolA for the first time in vitro. The obtained enzyme is able to efficiently catalyze DNA-dependent DNA synthesis requiring Mg(II) as divalent metal ion. Additionally, strand displacement synthesis of the DNA polymerase, which is required in several repair processes, could be detected. We further found that DNA polymerase function of PolA is modulated by the presence of Mn(II). Whereas proceeding DNA synthesis of PolA was blocked by certain DNA damage that occurs through radiation of DNA, bypass was facilitated by Mn(II). Our results suggest an enzyme modulator function of Mn(II). These observations parallel reports that D. radiodurans accumulates intracellular Mn(II) in cases of irradiation and that the level of irradiation protection correlates with Mn(II) concentrations.

Received for publication, December 13, 2006 , and in revised form, February 6, 2007.

^* The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

¹ To whom correspondence should be addressed: Universitätsstrasse 10, 78457 Konstanz, Germany. Tel.: 49-7531-88-5139; Fax: 49-7531-88-5140; E-mail: andreas.marx{at}uni-konstanz.de.

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