title: Microinjection of the nonhistone chromosomal protein HMG1 into bovine fibroblasts and HeLa cells.
abstract: The nonhistone chromosomal protein HMG1 associated rapidly with the nuclei of HeLa cells and bovine fibroblasts following its introduction into the cytoplasm by red cell-mediated microinjection. A number of non-nuclear proteins, on the other hand, failed to concentrate in HeLa or bovine fibroblast nuclei. Autoradiography of thin sections showed that 125I-labeled HMG1 localized within nuclei, and further established that it remained associated with metaphase chromosomes at mitosis. When uninjected HeLa cells were fused with 125I-HMG1-injected HeLa cells, the labeled molecules equilibrated between nuclei within 12 hr. Similar results were obtained with bovine fibroblasts, indicating that a dynamic equilibrium exists between HMG1 and chromatin within living cells. Electrophoresis of 125I-HMG1 retrieved from HeLa cells or bovine fibroblasts up to 48 hr after injection showed that more than 80% of the molecules were intact. Autoradiographic analysis of cells fixed over a period of several days after injection produced apparent half-lives for 125I-HMG1 of 80 hr in HeLa cells and 100 hr in bovine fibroblasts.
mesh_terms: D002459:Cell Fusion; D002467:Cell Nucleus / Q000378:metabolism*; D002478:Cells, Cultured; D002868:Chromosomal Proteins, Non-Histone / Q000378:metabolism*; D004912:Erythrocytes; D005260:Female; D005347:Fibroblasts; D006367:HeLa Cells; D006801:Humans; D007700:Kinetics; D008845:Microinjections / Q000379:methods; D008938:Mitosis
chemical_list: D002868:Chromosomal Proteins, Non-Histone