HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

J. Biol. Chem., Vol. 282, Issue 38, 28004-28013, September 21, 2007

This Article Full Text Full Text (PDF) Supplemental Data All Versions of this Article: 282/38/28004    most recent M704867200v1 Submit a Letter to Editor Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Permissions Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Mani, R. S. Articles by Weinfeld, M. Search for Related Content PubMed PubMed Citation Articles by Mani, R. S. Articles by Weinfeld, M. Social Bookmarking                      What's this?

XRCC1 Stimulates Polynucleotide Kinase by Enhancing Its Damage Discrimination and Displacement from DNA Repair Intermediates^*

Rajam S. Mani, Mesfin Fanta, Feridoun Karimi-Busheri, Elizabeth Silver, César A. Virgen, Keith W. Caldecott^¶, Carol E. Cass¹, and Michael Weinfeld²

From the Department of Experimental Oncology, Cross Cancer Institute, and the Department of Oncology, University of Alberta, Edmonton, Alberta T6G 1Z2, Canada and the ^¶Genome Damage and Stability Centre, University of Sussex, Science Park Road, Falmer, Brighton BN1 9RQ, United Kingdom

Human polynucleotide kinase (hPNK) is required for processing and rejoining DNA strand break termini. The 5'-DNA kinase and 3'-phosphatase activities of hPNK can be stimulated by the "scaffold" protein XRCC1, but the mechanism remains to be fully elucidated. Using a variety of fluorescence techniques, we examined the interaction of hPNK with XRCC1 and substrates that model DNA single-strand breaks. hPNK binding to substrates with 5'-OH termini was only 5-fold tighter than that to identical DNA molecules with 5'-phosphate termini, suggesting that hPNK remains bound to the product of its enzymatic activity. The presence of XRCC1 did not influence the binding of hPNK to substrates with 5'-OH termini, but sharply reduced the interaction of hPNK with DNA bearing a 5'-phosphate terminus. These data, together with kinetic data obtained at limiting enzyme concentration, indicate a dual function for the interaction of XRCC1 with hPNK. First, XRCC1 enhances the capacity of hPNK to discriminate between strand breaks with 5'-OH termini and those with 5'-phosphate termini; and second, XRCC1 stimulates hPNK activity by displacing hPNK from the phosphorylated DNA product.

Received for publication, June 13, 2007 , and in revised form, July 19, 2007.

^* This work was supported by the Canadian Institutes of Health Research, the Alberta Cancer Board, the Alberta Cancer Foundation, and the Alberta Heritage Foundation for Medical Research. 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.

The on-line version of this article (available at http://www.jbc.org) contains supplemental Fig. 1.

¹ Canada Research Chair in Oncology.

² To whom correspondence should be addressed: Dept. of Experimental Oncology, Cross Cancer Inst., 11560 University Ave., Edmonton, Alberta T6G 1Z2, Canada. Tel.: 780-432-8438; Fax: 780-432-8428; E-mail: michaelw{at}cancerboard.ab.ca.

CiteULike    Complore    Connotea    Del.icio.us    Digg    Reddit    Technorati    What's this?