title: Some properties of the small homodisperse RNAs in the cytoplasm of HeLa cells.
abstract: Two homodisperse, methylated, small molecular weight RNAs, that have been previously described in HeLa cells and that are apparently coded by the nuclear genome, appear in the cytoplasm shortly after transcription and are detected in the cytoplasm with a half-life of a few minutes. Under the denaturing conditions of urea-polyacrylamide gel electrophoresis, the migration of these RNAs indicated nucleotide lengths around 190 (A) and 160 (B). Neither A nor B RNAs differed in their electrophoretic mobility when comparing samples from 10 to 120 min incubation with [3H]uridine. When the detergent-treated postmitochondrial fraction from cells incubated for 60 min with [3H]-uridine was centrifuged through a 0.3 M NaC1/0.5 M sucrose cushion, the resulting pellet showed a marked increase in the ratio of counts A/4 S RNA, and particularly B/4 S RNA, suggesting that these RNAs might not exist free in the cytoplasm. At low concentrations of camptothecin (1-2.5 mug/ml), the accumulation of A and B RNA was greatly suppressed, while the synthesis of 4 S and 5 S RNA was less affected. Their accumulation (particularly that of B RNA) was enhanced when cells were exposed to inhibitors of various steps of protein synthesis (puromycin, cycloheximide, pactamycin, emetine). Pulse-chase experiments with actinomycin D during suppression of protein synthesis indicated that, at least in the case of B RNA, this increased accumulation was due, at least partly, to a marked prolongation of its half-life.
mesh_terms: D002166:Camptothecin / Q000494:pharmacology; D003513:Cycloheximide / Q000494:pharmacology; D003593:Cytoplasm / Q000032:analysis / Q000187:drug effects / Q000378:metabolism; D006367:HeLa Cells / Q000187:drug effects / Q000378:metabolism*; D010142:Pactamycin / Q000494:pharmacology; D011691:Puromycin / Q000494:pharmacology; D012334:RNA, Neoplasm / Q000378:metabolism
chemical_list: D012334:RNA, Neoplasm; D010142:Pactamycin; D011691:Puromycin; D003513:Cycloheximide; D002166:Camptothecin