Nucleocytoplasmic translocation of ribosomal RNA in the rabbit blastocyst: participation of sulfhydryl groups.
The release of ribosomes from the nucleus in the rabbit blastocyst was investigated by pulse-labeling embryos to within 5 min of the earliest appearance of radiolabeled ribosomal RNA (rRNA) in the cytoplasmic fraction. The accumulation of radiolabeled 4.7 and 1.9 kilobase mature rRNA species in the cytoplasm was then followed during a 2 hour chase period, using polyacrylamide gel electrophoresis to identify the rRNAs. Colchicine, cytochalasin B, KCN, and EDTA were found to have no effect on the release of radiolabeled rRNA from the blastocyst nucleus during the 2 hour chase. Oligomycin, a known inhibitor of the nuclear envelope nucleoside triphosphatase, and the protein synthesis inhibitors puromycin and cycloheximide blocked rRNA release after a short delay. In contrast, actinomycin D and the sulfhydryl-reactive agents N-ethylmaleimide and diamide produced an abrupt and complete block to further rRNA release. The results indicate that ribosomes leave the nuclear compartment by an energy-dependent process. They further underscore the importance of reduced sulfhydryl groups in a rapidly growing blastocyst with a high level of oxidative metabolism.
Manes
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Department of Biology, University of San Diego, California 92110.
D000818:Animals; D001755:Blastocyst / Q000737:chemistry / Q000378:metabolism*; D002458:Cell Fractionation; D002467:Cell Nucleus / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism*; D003609:Dactinomycin / Q000494:pharmacology; D003958:Diamide / Q000494:pharmacology; D004591:Electrophoresis, Polyacrylamide Gel; D005033:Ethylmaleimide / Q000494:pharmacology; D009840:Oligomycins / Q000494:pharmacology; D012335:RNA, Ribosomal / Q000378:metabolism*; D011817:Rabbits; D012270:Ribosomes / Q000378:metabolism* / Q000648:ultrastructure; D013438:Sulfhydryl Compounds / Q000037:antagonists & inhibitors / Q000378:metabolism*
D009840:Oligomycins; D012335:RNA, Ribosomal; D013438:Sulfhydryl Compounds; D003958:Diamide; D003609:Dactinomycin; D005033:Ethylmaleimide