Nucleic Acids Research Advance Access originally published online on October 4, 2007
Nucleic Acids Research 2007 35(19):6672-6680; doi:10.1093/nar/gkm567
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Nucleic Acids Research, 2007, Vol. 35, No. 19 6672-6680
© 2007 The Author(s)
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/2.0/uk/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Nucleic Acid Enzymes |
Escherichia coli HU protein has a role in the repair of abasic sites in DNA
1Department of Radiation Oncology, Emory University School of Medicine, 2Department of Pathology, Clifton Road NE, Atlanta, GA 30322 and 3Division of Diagnostic Sciences and Department of Molecular and Computational Biology, University of Southern California, Los Angeles, CA 90089, USA
*To whom correspondence should be addressed. Tel: +1 404 778 5481; Fax: +1 404 778 3965; Email: ykow{at}emory.edu
Received June 4, 2007. Revised July 5, 2007. Accepted July 6, 2007.
HU is one of the most abundant DNA binding proteins in Escherichia coli. We find that it binds strongly to DNA containing an abasic (AP) site or tetrahydrofuran (THF) (apparent Kd 
50 nM). It also possesses an AP lyase activity that cleaves at a deoxyribose but not at a THF residue. The binding and cleavage of an AP site was observed only with the HU
ß heterodimer. Site-specific mutations at K3 and R61 residues led to a change in substrate binding and cleavage. Both K3A()K3A(ß) and R61A()R61A(ß) mutant HU showed significant reduction in binding to DNA containing AP site; however, only R61A()R61A(ß) mutant protein exhibited significant loss in AP lyase activity. Both K3A()K3A(ß) and R61K()R61K(ß) showed slight reduction in AP lyase activities. The function of HU protein as an AP lyase was confirmed by the ability of hupA or hupB mutations to further reduce the viability of an E. coli dut(Ts) xth mutant, which generates lethal AP sites at 37°C; the hupA and hupB derivatives, respectively, had a 6-fold and a 150-fold lower survival at 37°C than did the parental strain. These data suggest, therefore, that HU protein plays a significant role in the repair of AP sites in E. coli.