title: Changes in p34cdc2 kinase activity and cyclin A during induced differentiation of murine erythroleukemia cells.
abstract: Hexamethylene bisacetamide (HMBA)-induced murine erythroleukemia (MELC) differentiation is characterized by a prolongation of the initial G1 which follows passage through S phase in the presence of inducer. Commitment to terminal cell division is first detected in a portion of the cell population during this prolonged G1. HMBA-induced commitment is stochastic. This study has examined changes in two known cell cycle regulators, p34cdc2 and cyclin A, in cycle-synchronized MELC in the absence and presence of HMBA. Histone H1 kinase activity of p34cdc2, and the levels of CDC2Mm mRNA, 1.8-kilobase mRNA of cyclin A, and cyclin A protein changed during cell cycle progression in MELC, and all of them were suppressed during G1. The suppression of the H1 kinase activity and cyclin A expression continued through the prolonged G1 in MELC cultured with HMBA, whereas p34cdc2 protein level did not vary through the cell cycle in MELC cultured without or with inducer. Phosphorylation of p34cdc2 in uninduced MELC gradually increased as cells progressed from G1 to S. In induced MELC, an increase in phosphorylation of p34cdc2 occurred during the prolonged G1, and prior to the exit of the bulk of the cells from G1 to S. These results suggest that in HMBA-induced MELC, p34cdc2 phosphorylation per se is not a limiting factor in determining G1 to S progression. The persistent suppression of cyclin A expression and histone H1 kinase activity may play a role in HMBA-induced commitment to terminal differentiation.
authors.affiliation: DeWitt Wallace Research Laboratory, Memorial Sloan-Kettering Cancer Center, New York, New York 10021.
authors.forename: H
authors.initials: H
authors.lastname: Kiyokawa
authors.forename: L
authors.initials: L
authors.lastname: Ngo
authors.forename: T
authors.initials: T
authors.lastname: Kurosaki
authors.forename: R A
authors.initials: RA
authors.lastname: Rifkind
authors.forename: P A
authors.initials: PA
authors.lastname: Marks
mesh_terms: D000081:Acetamides / Q000494:pharmacology; D000818:Animals; D001483:Base Sequence; D016203:CDC2 Protein Kinase / Q000032:analysis*; D002453:Cell Cycle; D002454:Cell Differentiation; D016213:Cyclins / Q000032:analysis*; D004789:Enzyme Activation / Q000187:drug effects; D004915:Leukemia, Erythroblastic, Acute; D051379:Mice; D008969:Molecular Sequence Data; D010766:Phosphorylation; D012333:RNA, Messenger / Q000032:analysis; D014407:Tumor Cells, Cultured / Q000187:drug effects
chemical_list: D000081:Acetamides; D016213:Cyclins; D012333:RNA, Messenger; D016203:CDC2 Protein Kinase; C014026:hexamethylene bisacetamide