title: Late S phase cells (Chinese hamster ovary) induce early S phase DNA labeling patterns in G1 phase nuclei.
abstract: Cells (Chinese hamster ovary) in G1 phase were fused with cells in late S phase to determine if a cell in late S phase can induce DNA synthesis in the nucleus of a G1 cell and, if so, to determine if the DNA synthesis so induced in a G1 phase nucleus has an autoradiographic pattern characteristic of early or of late S phase synthesis. The results indicate (i) that 89% of the G1 nuclei in late-S/G1 binucleates synthesized DNA, while only 2% of the control unfused G1 cells synthesized DNA, and (ii) that in all late-S/G1 binucleates the G1 nucleus was induced to synthesize early S phase DNA. These results are compatible with the idea that a cytoplasmically transmissible factor initiates DNA synthesis but that an intranuclear mechanism defines the temporal order of replication.
mesh_terms: D002453:Cell Cycle; D002459:Cell Fusion; D002460:Cell Line; D002466:Cell Nucleolus / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism; D002843:Chromatin / Q000378:metabolism; D004261:DNA Replication; D006570:Heterochromatin / Q000378:metabolism; D006822:Hybrid Cells / Q000378:metabolism*
chemical_list: D002843:Chromatin; D006570:Heterochromatin