Alteration of ribosomal precursor RNA in Novikoff hepatoma cells by 5-azacytidine: Studies on methylation of 45S and 32S RNA

Abstract

5-Azacytidine, which has been shown to inhibit the maturation of ribosomal RNA from its precursors when added to the medium of cultured Novikoff hepatoma cells, alters the electrophoretic mobilities of the 45S and 32S ribosomal RNA precursors formed in Novikoff cells. Coelectrophoresis of total cell RNA samples shows that the 45S and 32S RNA precursors from 5-azacytidine-treated cells migrate slower than the corresponding precursors from control cells. 5-Azacytidine causes some reduction in the rate and degree of methylation of the 45S and 32S RNA precursors; however, the alteration in electrophoretic mobility and maturation of these two RNA species do not appear to be a consequence of undermethylation. Coelectrophoresis of undermethylated RNA produced by methionine starvation with normal RNA shows no differences in mobility of the ribosomal precursor RNA s. 5-Fluorouridine and 8-azaguanine, also inhibitors of ribosomal RNA maturation, were not found to cause detectable differences in migration of the ribosomal precursor RNA s.