title: Inhibitor of ribosomal RNA synthesis in Xenopus laevis embryos. VII. Inhibition of 40s pre-rRNA synthesis in Xenopus neurula cells.
abstract: A fraction containing acid-soluble materials (PCA-extract) from Xenopus early blastulae preferentially inhibits the incorporation of [3H]uridine into 18S and 28S rRNA in Xenopus neurula cells. Pulse- laneling experiments revealed that whereas tubercidin, a known inhibitor of rRNA processing, produced a marked accumulation of the label in 40S pre-rRNA, Xenopus inhibitor suppressed labeling of the pre-rRNA. When tubercidin was added to cells whose activity for rRNA synthesis had been lowered by the Xenopus inhibitor, there was still an accumulation of label in the pre-rRNA. These results indicate that Xenopus inhibitor suppresses the synthesis of rRNA at transcription rather than at processing.
mesh_terms: D000818:Animals; D001755:Blastocyst / Q000502:physiology*; D012335:RNA, Ribosomal / Q000037:antagonists & inhibitors* / Q000096:biosynthesis; D014020:Tissue Extracts / Q000494:pharmacology*; D014158:Transcription, Genetic / Q000187:drug effects; D014372:Tubercidin / Q000494:pharmacology; D014982:Xenopus laevis / Q000196:embryology*
chemical_list: D012335:RNA, Ribosomal; D014020:Tissue Extracts; D014372:Tubercidin