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Crude extracts from replicating normal and transformed cells were assayed for protein kinase activities specific for different sites in purified Hl histone in vitro. Extracts from normal cells favored the NH2-terminal region while extracts from transformed cells favored the COOH-terminal region. Analysis of phosphopeptides demonstrated that histone kinases from both normal and transformed cells catalyzed the phosphorylation of a number of sites in common, and these were typical of sites phosphorylated in replicating cells. The preference for the NH2-terminal region by extracts from normal cells was due to the extensive phosphorylation of a site previously shown to be phosphorylated by cyclic AMP-dependent protein kinase. This activity was very low in transformed cells.