Synthesis and phosphorylation of chromatin-associated proteins in cAMP-induced "differentiated" neuroblastoma cells in culture.

Prostaglandin E, and a CAMP phosphodiesterase inhibitor 4-(3-butoxy-4-methoxybenzyl)-2imidazolidinone, R020-1724, were used to induce differentiation in mouse neuroblastoma cells in culture. The incorporation of amino acids and phosphate into nuclear proteins of control and drug-treated cells (1 h and 3 days after treatment) was examined using double radioisotopic techniques. A marked decrease in histone synthesis and HI-histone phosphorylation were observed in ‘differentiated’ neuroblastoma cells after 3 days of prostaglandin E, and R020-1724 treatment, but only small differences were noted in the synthesis and phosphorylation of nonhistone chromatin associated proteins after 3 days of drug treatment. Minimal changes were observed in the labeling of histone and non-histone nuclear proteins if the cells were treated for 1 h with prostaglandin E, and R020-1724.