Cell nonhomologous end joining capacity controls SAF-A phosphorylation by DNA-PK in response to DNA double-strand breaks inducers.
Aiming to identify novel phosphorylation sites in response to DNA double-strand breaks (DSB) inducers, we have isolated a phosphorylation site on KU70. Unexpectedly, a rabbit antiserum raised against this site cross-reacted with a 120 kDa protein in cells treated by DNA DSB inducers. We identified this protein as SAF-A/hnRNP U, an abundant and essential nuclear protein containing regions binding DNA or RNA. The phosphorylation site was mapped at S59 position in a sequence context favoring a "S-hydrophobic" consensus model for DNA-PK phosphorylation site in vivo. This site was exclusively phosphorylated by DNA-PK in response to DNA DSB inducers. In addition, the extent and duration of this phosphorylation was in inverse correlation with the capacity of the cells to repair DSB by Nonhomologous End Joining. These results bring a new link between the hnRNP family and the DNA damage response. Addtionaly, the mapped phospho-site on SAF-A might serve as a potential bio-marker for DNA-PK activity in academic studies and clinical analyses of DNA-PK activators or inhibitors.
CNRS, IPBS (Institut de Pharmacologie et de Biologie Structurale), Toulouse, France; Université de Toulouse, UPS, IPBS, Toulouse, France.
Sébastien
S
Britton
Carine
C
Froment
Philippe
P
Frit
Bernard
B
Monsarrat
Bernard
B
Salles
Patrick
P
Calsou
D000595:Amino Acid Sequence; D000818:Animals; D000906:Antibodies / Q000276:immunology; D034961:Antigens, Nuclear / Q000276:immunology / Q000378:metabolism; D001483:Base Sequence; D002460:Cell Line; D004247:DNA / Q000378:metabolism*; D053903:DNA Breaks, Double-Stranded; D004260:DNA Repair / Q000502:physiology*; D051747:DNA-Activated Protein Kinase / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000276:immunology / Q000378:metabolism; D034722:Heterogeneous-Nuclear Ribonucleoprotein U / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D015151:Immunoblotting; D047468:Immunoprecipitation; D000072200:Ku Autoantigen; D013058:Mass Spectrometry; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000378:metabolism*; D010766:Phosphorylation; D011817:Rabbits; D017422:Sequence Analysis, DNA
D000906:Antibodies; D034961:Antigens, Nuclear; D004268:DNA-Binding Proteins; D034722:Heterogeneous-Nuclear Ribonucleoprotein U; D009687:Nuclear Proteins; D004247:DNA; D051747:DNA-Activated Protein Kinase; C497263:PRKDC protein, human; C000606509:Xrcc6 protein, human; D000072200:Ku Autoantigen