title: Ku heterodimer binds to both ends of the Werner protein and functional interaction occurs at the Werner N-terminus.
abstract: The human Werner syndrome protein, WRN, is a member of the RecQ helicase family and contains 3'-->5' helicase and 3'-->5' exonuclease activities. Recently, we showed that the exonuclease activity of WRN is greatly stimulated by the human Ku heterodimer protein. We have now mapped this interaction physically and functionally. The Ku70 subunit specifically interacts with the N-terminus (amino acids 1-368) of WRN, while the Ku80 subunit interacts with its C-terminus (amino acids 940- 1432). Binding between Ku70 and the N-terminus of WRN (amino acids 1-368) is sufficient for stimulation of WRN exonuclease activity. A mutant Ku heterodimer of full-length Ku80 and truncated Ku70 (amino acids 430-542) interacts with C-WRN but not with N-WRN and cannot stimulate WRN exonuclease activity. This emphasizes the functional significance of the interaction between the N-terminus of WRN and Ku70. The interaction between Ku80 and the C-terminus of WRN may modulate some other, as yet unknown, function. The strong interaction between Ku and WRN suggests that these two proteins function together in one or more pathways of DNA metabolism.
authors.affiliation: Laboratory of Molecular Gerontology, Box 1, National Institute on Aging, IRP, National Institutes of Health, 5600 Nathan Shock Drive, Baltimore, MD 21224-6825, USA.
authors.forename: Parimal
authors.initials: P
authors.lastname: Karmakar
authors.forename: Carey M
authors.initials: CM
authors.lastname: Snowden
authors.forename: Dale A
authors.initials: DA
authors.lastname: Ramsden
authors.forename: Vilhelm A
authors.initials: VA
authors.lastname: Bohr
mesh_terms: D000818:Animals; D034961:Antigens, Nuclear; D001665:Binding Sites; D002460:Cell Line; D004247:DNA / Q000235:genetics / Q000378:metabolism; D004265:DNA Helicases / Q000737:chemistry* / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D019281:Dimerization; D024202:Electrophoretic Mobility Shift Assay; D005090:Exodeoxyribonucleases; D006801:Humans; D000072200:Ku Autoantigen; D009154:Mutation; D009687:Nuclear Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D021122:Protein Subunits; D053484:RecQ Helicases; D000071657:Werner Syndrome Helicase
chemical_list: D034961:Antigens, Nuclear; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D021122:Protein Subunits; D004247:DNA; D005090:Exodeoxyribonucleases; D004265:DNA Helicases; D053484:RecQ Helicases; C098785:WRN protein, human; D000071657:Werner Syndrome Helicase; C106893:XRCC5 protein, human; C000606509:Xrcc6 protein, human; D000072200:Ku Autoantigen