title: Degradation of nuclear proteins: studies on transplanted B82 cell karyoplast proteins.
abstract: Karyoplasts were prepared from B82 cells (thymidine kinase deficient mouse L cells) by cytochalasin B mediated enucleation. Morphological measurements show that the nucleus constitutes 89% of a karyoplast by volume. Homokaryons were obtained by Sendai virus mediated karyoplast-B82 cell fusion. Transplanted nuclei were not destroyed catastrophically but were maintained intracellularly for at least 140 h. Transplanted nuclear proteins were degraded with an average half-life of 84 +/- 7 h by processes partially sensitive to inhibition by NH4Cl (50%) and leupeptin (30%). The data therefore suggest that some nuclear proteins are translocated to the cytoplasm for lysosomal degradation.
mesh_terms: D000818:Animals; D002459:Cell Fusion; D002467:Cell Nucleus / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D007739:L Cells / Q000378:metabolism; D051379:Mice; D009698:Nucleoproteins / Q000378:metabolism*; D010222:Parainfluenza Virus 1, Human / Q000235:genetics; D013937:Thymidine Kinase / Q000172:deficiency
chemical_list: D009698:Nucleoproteins; D013937:Thymidine Kinase