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DNAâactivated protein kinase in Raji Burkitt's lymphoma cells: Phosphorylation of câMyc oncoprotein
- IIJIMA, Shigeyuki, TERAOKA, Hirobumi, DATE, Takayasu, TSUKADA, Kinji
- European journal of biochemistry 1992 v.206 no.2 pp. 595-603
- RNA, lymphoma, oncogene proteins, phosphoproteins, phosphorylation, polyacrylamide gel electrophoresis, protein kinases, serine, single-stranded DNA
- Autophosphorylation of a DNAâactivated protein kinase (DNAâPK) in Raji Burkitt's lymphoma cells generated a band that corresponded to a phosphoprotein of about 300 kDa on SDS/PAGE. This band corresponds to a 300â350âkDa DNAâPK found previously in HeLa cells. In addition to the 300âkDa phosphoprotein, the band of a highly phosphorylated 58âkDa protein was detected by SDS/PAGE of partially purified DNAâPK preparations after the phosphorylation reaction in the presence of doubleâstranded DNA. this phosphoprotein was specifically immunoprecipitated by mAb against câMyc. More highly purfied preparations of DNAâPK, containing neither a 58âkDa phosphoprotein nor detectable activities of other kinases, phosphorylated recombinant câMyc proteins in the presence of DNA. the câMyc phosphorylation by DNAâPK was markedly stimulated by relxed, doubleâstranded DNA, but neither by singleâstranded DNA nor by RNA. Phosphopeptide mapping and phosphoamino acid analysis indicated that DNAâPK phosphorylates câMyc in vitro at several serine residues.