DNA-stimulated protein phosphorylation in HeLa whole cell and nuclear extracts

Incorporation of 32P from gamma-labeled ATP into a number of polypeptides in HeLa whole cell and nuclear extracts was dependent on added double-stranded DNA or poly(dI-dC), but not denatured or supercoiled DNA. DNA-dependent phosphorylation of a high Mr endogenous substrate could be reconstituted from the precipitate formed after incubation of whole cell extracts with DNA. Fractionation of extracts by phosphocellulose or DEAE-Sephacel chromatography yielded preparations that phosphorylated casein as well as endogenous polypeptides in a DNA-dependent manner. These results are consistent with the existence of a novel protein kinase in HeLa cells that is highly dependent upon the presence of double-stranded DNA for efficient phosphorylation of a variety of substrates.