title: Stimulation of DNA synthesis by an inositol polyphosphate-activated protein phosphatase in calcium-deprived rat liver cells.
abstract: Specific stages of the prereplicative G1 phase of the cell cycle in nonneoplastic cells requires extracellular Ca2+ for successful transition. These are the G0-G1 and the G1-S transitions. A variety of agents are able to replace Ca2+ and to at least partially stimulate cells to replicate their chromosomes. One of these agonist, inositol 1,3,4,5-tetrakisphosphate [Ins(1,3,4,5)P4], has been demonstrated by us to also stimulate the activity of a phosphoprotein phosphatase. The addition of a purified preparation of the protein phosphatase to Ca2(+)-deprived G1-S-blocked T51B rat liver cells stimulates a rapidly responding fraction of cells to enter their S phase, and this effect is blocked by protein phosphatase inhibitors heparin and inhibitor 2.
authors.affiliation: Cancer Research Center, University of Hawaii, Honolulu 96813.
authors.forename: J
authors.initials: J
authors.lastname: Zwiller
authors.forename: R E
authors.initials: RE
authors.lastname: Honkanen
authors.forename: A L
authors.initials: AL
authors.lastname: Boynton
mesh_terms: D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D002453:Cell Cycle / Q000187:drug effects; D002460:Cell Line; D004261:DNA Replication / Q000187:drug effects*; D004847:Epithelial Cells; D004848:Epithelium / Q000187:drug effects / Q000378:metabolism; D006493:Heparin / Q000494:pharmacology; D015544:Inositol 1,4,5-Trisphosphate / Q000494:pharmacology*; D007295:Inositol Phosphates / Q000494:pharmacology*; D007700:Kinetics; D008099:Liver / Q000378:metabolism*; D010749:Phosphoprotein Phosphatases / Q000378:metabolism*; D051381:Rats; D013936:Thymidine / Q000378:metabolism
chemical_list: D007295:Inositol Phosphates; C081655:inositol-1,3,4,5-tetrakisphosphate; D015544:Inositol 1,4,5-Trisphosphate; D006493:Heparin; D010749:Phosphoprotein Phosphatases; D002118:Calcium; D013936:Thymidine