title: KARP-1: a novel leucine zipper protein expressed from the Ku86 autoantigen locus is implicated in the control of DNA-dependent protein kinase activity.
abstract: The Ku autoantigen plays an integral role in mammalian DNA double-strand break repair as the DNA binding component of the DNA-dependent protein kinase (DNA-PK) complex. Here, we demonstrate that a second gene, KARP-1 (Ku86 Autoantigen Related Protein-1), is expressed from the Ku86 locus. The KARP-1 gene utilizes an upstream promoter and additional exons which results in an extra 9 kDa of protein appended onto the normal Ku86 polypeptide. The KARP-1-specific domain encodes interdigitating hexa- and penta-heptad repeats of leucine residues flanked by a very basic region. Intriguingly, the catalytic subunit of DNA-PK also contains a hexa-heptad repeat of leucines. Consistent with this observation, we observed that human cell lines stably expressing dominant-negative constructs of KARP-1 resulted in diminished DNA-PK activity and X-ray hypersensitivity and that a KARP-1 antibody significantly neutralized DNA-PK activity in vitro. Finally, we present data which suggests that KARP-1 may be primate-specific. These observations have important repercussions for mammalian DNA double-strand break repair.
authors.affiliation: Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, RI 02912, USA.
authors.forename: K
authors.initials: K
authors.lastname: Myung
authors.forename: D M
authors.initials: DM
authors.lastname: He
authors.forename: S E
authors.initials: SE
authors.lastname: Lee
authors.forename: E A
authors.initials: EA
authors.lastname: Hendrickson
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D034961:Antigens, Nuclear; D001324:Autoantigens / Q000235:genetics*; D001483:Base Sequence; D002352:Carrier Proteins / Q000235:genetics* / Q000378:metabolism; D006224:Cricetinae; D004265:DNA Helicases; D004260:DNA Repair / Q000235:genetics*; D018076:DNA, Complementary / Q000235:genetics; D051747:DNA-Activated Protein Kinase; D004268:DNA-Binding Proteins / Q000235:genetics*; D006801:Humans; D000072200:Ku Autoantigen; D016350:Leucine Zippers; D008957:Models, Genetic; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000235:genetics*; D009693:Nucleic Acid Hybridization; D016366:Open Reading Frames; D011323:Primates; D011401:Promoter Regions, Genetic; D017346:Protein Serine-Threonine Kinases / Q000096:biosynthesis*; D017433:Protein Structure, Secondary; D012333:RNA, Messenger / Q000096:biosynthesis; D017386:Sequence Homology, Amino Acid; D013045:Species Specificity; D014158:Transcription, Genetic
chemical_list: D034961:Antigens, Nuclear; D001324:Autoantigens; D002352:Carrier Proteins; D018076:DNA, Complementary; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D012333:RNA, Messenger; D051747:DNA-Activated Protein Kinase; C497263:PRKDC protein, human; D017346:Protein Serine-Threonine Kinases; D004265:DNA Helicases; C106893:XRCC5 protein, human; C000606509:Xrcc6 protein, human; D000072200:Ku Autoantigen