DNA-dependent protein kinase (DNA-PK) phosphorylates nuclear DNA helicase II/RNA helicase A and hnRNP proteins in an RNA-dependent manner.
An RNA-dependent association of Ku antigen with nuclear DNA helicase II (NDH II), alternatively named RNA helicase A (RHA), was found in nuclear extracts of HeLa cells by immunoprecipitation and by gel filtration chromatography. Both Ku antigen and NDH II were associated with hnRNP complexes. Two-dimensional gel electrophoresis showed that Ku antigen was most abundantly associated with hnRNP C, K, J, H and F, but apparently not with others, such as hnRNP A1. Unexpectedly, DNA-dependent protein kinase (DNA-PK), which comprises Ku antigen as the DNA binding subunit, phosphorylated hnRNP proteins in an RNA-dependent manner. DNA-PK also phosphorylated recombinant NDH II in the presence of RNA. RNA binding assays displayed a preference of DNA-PK for poly(rG), but not for poly(rA), poly(rC) or poly(rU). This RNA binding affinity of DNA-PK can be ascribed to its Ku86 subunit. Consistently, poly(rG) most strongly stimulated the DNA-PK-catalyzed phosphorylation of NDH II. RNA interference studies revealed that a suppressed expression of NDH II altered the nuclear distribution of hnRNP C, while silencing DNA-PK changed the subnuclear distribution of NDH II and hnRNP C. These results support the view that DNA-PK can also function as an RNA-dependent protein kinase to regulate some aspects of RNA metabolism, such as RNA processing and transport.
Zhang
Suisheng
S
Department of Biochemistry, Institute of Molecular Biotechnology, Postfach 100 813, D-07708 Jena, Germany.
Schlott
Bernhard
B
Görlach
Matthias
M
Grosse
Frank
F
D000251:Adenosine Triphosphatases / Q000235:genetics / Q000378:metabolism*; D034961:Antigens, Nuclear / Q000378:metabolism; D001324:Autoantigens / Q000235:genetics / Q000378:metabolism*; D002457:Cell Extracts; D053487:DEAD-box RNA Helicases; D004265:DNA Helicases / Q000235:genetics / Q000378:metabolism*; D051747:DNA-Activated Protein Kinase; D004268:DNA-Binding Proteins / Q000378:metabolism; D006367:HeLa Cells; D034441:Heterogeneous-Nuclear Ribonucleoproteins / Q000378:metabolism*; D006801:Humans; D000072200:Ku Autoantigen; D046911:Macromolecular Substances; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism*; D009687:Nuclear Proteins; D010766:Phosphorylation; D011233:Precipitin Tests; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D012313:RNA / Q000378:metabolism*; D020365:RNA Helicases / Q000235:genetics / Q000378:metabolism*; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000737:chemistry / Q000378:metabolism
D034961:Antigens, Nuclear; D001324:Autoantigens; D002457:Cell Extracts; D004268:DNA-Binding Proteins; D034441:Heterogeneous-Nuclear Ribonucleoproteins; D046911:Macromolecular Substances; D008565:Membrane Proteins; D009363:Neoplasm Proteins; D009687:Nuclear Proteins; D034741:RNA, Small Interfering; D016601:RNA-Binding Proteins; D012313:RNA; D051747:DNA-Activated Protein Kinase; C497263:PRKDC protein, human; D017346:Protein Serine-Threonine Kinases; D000251:Adenosine Triphosphatases; C098487:DHX9 protein, human; D004265:DNA Helicases; C106893:XRCC5 protein, human; C000606509:Xrcc6 protein, human; D053487:DEAD-box RNA Helicases; D020365:RNA Helicases; D000072200:Ku Autoantigen