title: DNA polymerase alpha and the regulation of entry into S phase in heterokaryons.
abstract: We have previously reported that the DNA polymerase alpha activity/unit cellular protein is decreased in late-passage (senescent) human diploid fibroblast-like (HDFL) cultures due to the cellular enlargement associated with in vitro aging. In the studies described here, we have used cell fusion technology to investigate the formal kinetic relationship between the concentration of DNA polymerase alpha and the rate of reinitiation of DNA synthesis in nuclei from senescent cells. Heterokaryons were derived from the fusion of senescent cells to a series of actively dividing cell types with inherently different DNA polymerase alpha activities per cell. A kinetic analysis revealed a first-order relationship between the entry into S phase of senescent nuclei and the concentration of DNA polymerase alpha activity calculated to be in heterokaryons. This result suggests that increases in cell volume may be related to the decline in proliferative activity of late-passage HDFL cells, via "dilution" of factors essential for cellular replication.
authors.affiliation: Department of Pathology, University of Washington, Seattle 98195.
authors.forename: W R
authors.initials: WR
authors.lastname: Pendergrass
authors.forename: J C
authors.initials: JC
authors.lastname: Angello
authors.forename: A C
authors.initials: AC
authors.lastname: Saulewicz
authors.forename: T H
authors.initials: TH
authors.lastname: Norwood
mesh_terms: D002455:Cell Division / Q000502:physiology; D002459:Cell Fusion; D002461:Cell Line, Transformed; D002467:Cell Nucleus / Q000378:metabolism*; D002469:Cell Separation; D002470:Cell Survival / Q000502:physiology; D004257:DNA Polymerase II / Q000502:physiology*; D004261:DNA Replication / Q000502:physiology*; D005347:Fibroblasts / Q000166:cytology / Q000201:enzymology*; D006367:HeLa Cells; D006801:Humans; D007700:Kinetics; D016196:S Phase / Q000235:genetics
chemical_list: D004257:DNA Polymerase II