The binding of Ku antigen to homeodomain proteins promotes their phosphorylation by DNA-dependent protein kinase.
The Ku antigen (70- and 80-kDa subunits) is a regulatory subunit of DNA-dependent protein kinase (DNA-PK) that promotes the recruitment of the catalytic subunit of DNA-PK (DNA-PKcs) to DNA ends and to specific DNA sequences from which the kinase is activated. Ku and DNA-PKcs plays essential roles in double-stranded DNA break repair and V(D)J recombination and have been implicated in the regulation of specific gene transcription. In a yeast two-hybrid screen of a Jurkat T cell cDNA library, we have identified a specific interaction between the 70-kDa subunit of Ku heterodimer and the homeodomain of HOXC4, a homeodomain protein expressed in the hematopoietic system. Unexpectedly, a similar interaction with Ku was observed for several additional homeodomain proteins including octamer transcription factors 1 and 2 and Dlx2, suggesting that specific binding to Ku may be a property shared by many homeodomain proteins. Ku-homeodomain binding was mediated through the extreme C terminus of Ku70 and was abrogated by amino acid substitutions at Lys595/Lys596. Ku binding allowed the recruitment of the homeodomain to DNA ends and dramatically enhanced the phosphorylation of homeodomain-containing proteins by DNA-PK. These results suggest that Ku functions as a substrate docking protein for signaling by DNA-PK to homeodomain proteins from DNA ends.
Department of Medicine, The Loeb Health Research Institute at the Ottawa Hospital, University of Ottawa, Ottawa, Ontario K1Y 4E9, Canada.
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Schild-Poulter
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Pope
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Giffin
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JC
Kochan
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Ngsee
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Traykova-Andonova
R J
RJ
Haché
D000324:Adrenocorticotropic Hormone / Q000235:genetics; D000595:Amino Acid Sequence; D000818:Animals; D034961:Antigens, Nuclear; D002645:Chickens; D003001:Cloning, Molecular; D006224:Cricetinae; D004265:DNA Helicases; D051747:DNA-Activated Protein Kinase; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D019281:Dimerization; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism; D005786:Gene Expression Regulation; D018398:Homeodomain Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D019169:Jurkat Cells; D000072200:Ku Autoantigen; D051379:Mice; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D050813:Octamer Transcription Factor-2; D010766:Phosphorylation; D011485:Protein Binding; D014176:Protein Biosynthesis; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins; D016415:Sequence Alignment; D017384:Sequence Deletion; D017386:Sequence Homology, Amino Acid; D013987:Ticks; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic; D014981:Xenopus
D034961:Antigens, Nuclear; D004268:DNA-Binding Proteins; D005656:Fungal Proteins; C052130:GAL4 protein, S cerevisiae; C098691:HOXC4 protein, human; D018398:Homeodomain Proteins; C490904:Hoxc4 protein, mouse; D009687:Nuclear Proteins; D050813:Octamer Transcription Factor-2; C058435:POU2F2 protein, human; C489206:Pou2f2 protein, mouse; D011994:Recombinant Proteins; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; C081647:high affinity DNA-binding factor, S cerevisiae; D000324:Adrenocorticotropic Hormone; 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; C000606510:Xrcc6 protein, mouse; D000072200:Ku Autoantigen