Distribution of the regulatory subunit of type II cAMP-dependent protein kinase in Y-79 retinoblastoma cells. Effect of butyrate

An indirect immunofluorescence technique was employed to determine the intracellular distribution of the regulatory subunit of type II cyclic adenosine 3':5'-monophosphate-dependent protein kinase (RII) in Y-79 human retinoblastoma cells growing in monolayer culture. During the initial phases of growth (6 hr-6 days after seeding), RII was confined to the cytoplasmic areas of the Y-79 cells, seemingly, the Golgi apparatus. Treatment of cells for 3-5 days with 4 mM butyrate resulted in translocation of RII from cytoplasm to nuclei (mainly nucleoli) of cells. In a later stage of growth (24-day-old cultures), RII immunofluorescence was significantly decreased in all compartments within the untreated cells. In contrast, about 70% of the butyrate-treated cells yet showed nucleoli and/or cytoplasmic localization of RII at this stage. The nucleolar appearance of RII was parallel to the growth arrest and differentiation induced by butyrate.