title: Werner syndrome protein. II. Characterization of the integral 3' --> 5' DNA exonuclease.
abstract: In addition to its DNA helicase activity, Werner syndrome protein (WRN) also possesses an exonuclease activity (Shen, J.-C., Gray, M. D., Kamath-Loeb, A. S., Fry, M., Oshima, J., and Loeb, L. A. (1998) J. Biol. Chem. 273, 34139-34144). Here we describe the properties of nearly homogeneous WRN exonuclease. WRN exonuclease hydrolyzes a recessed strand in a partial DNA duplex but does not significantly digest single-stranded DNA, blunt-ended duplex, or a protruding strand of a partial duplex. Although DNA is hydrolyzed in the absence of nucleoside triphosphates, nuclease activity is markedly stimulated by ATP, dATP, or CTP. WRN exonuclease digests DNA with a 3' --> 5' directionality to generate 5'-dNMP products, and DNA strands terminating with either a 3'-OH or 3'-PO4 group are hydrolyzed to similar extents. A recessed DNA strand with a single 3'-terminal mismatch is hydrolyzed more efficiently by WRN than one with a complementary nucleotide, but the enzyme fails to hydrolyze a DNA strand terminating with two mismatched bases. WRN exonuclease is distinguished from known mammalian DNA nucleases by its covalent association with a DNA helicase, preference for a recessed DNA strand, stimulation by ATP, ability to equally digest DNA with 3'-OH or 3'-PO4 termini, and its preferential digestion of DNA with a single 3'-terminal mismatch.
authors.affiliation: Gottstein Memorial Cancer Research Laboratory, Departments of Pathology and Biochemistry, University of Washington, Seattle, Washington 98195-7705, USA. laloeb@u.washington.edu
authors.forename: A S
authors.initials: AS
authors.lastname: Kamath-Loeb
authors.forename: J C
authors.initials: JC
authors.lastname: Shen
authors.forename: L A
authors.initials: LA
authors.lastname: Loeb
authors.forename: M
authors.initials: M
authors.lastname: Fry
mesh_terms: D001483:Base Sequence; D004247:DNA / Q000378:metabolism; D004265:DNA Helicases / Q000378:metabolism*; D004277:DNA, Single-Stranded / Q000378:metabolism; D003854:Deoxyribonucleotides / Q000494:pharmacology; D004706:Endodeoxyribonucleases / Q000378:metabolism*; D005090:Exodeoxyribonucleases; D006801:Humans; D006868:Hydrolysis; D007700:Kinetics; D008969:Molecular Sequence Data; D009838:Oligodeoxyribonucleotides / Q000737:chemistry / Q000378:metabolism*; D053484:RecQ Helicases; D012265:Ribonucleotides / Q000494:pharmacology; D013379:Substrate Specificity; D014898:Werner Syndrome / Q000201:enzymology*; D000071657:Werner Syndrome Helicase
chemical_list: D004277:DNA, Single-Stranded; D003854:Deoxyribonucleotides; D009838:Oligodeoxyribonucleotides; D012265:Ribonucleotides; D004247:DNA; D004706:Endodeoxyribonucleases; D005090:Exodeoxyribonucleases; C026044:deoxyribonuclease V; D004265:DNA Helicases; D053484:RecQ Helicases; C098785:WRN protein, human; D000071657:Werner Syndrome Helicase