tsJT16, a cell-cycle ts mutant defective in a function operating soon after growth stimulation, fails to induce a primarily activated labile nuclear protein.
tsJT16 is a temperature-sensitive (ts) mutant of rat fibroblasts that has a ts defect in a function operating soon after the growth stimulation from the G0 phase. After the growth stimulation, the cells express several cell-cycle-dependent genes at both temperatures while they fail at the nonpermissive temperature to synthesize a protein p70 identified on two-dimensional gel electrophoresis. Here we report that 1) synthesis of p70 began within 1 h of stimulation, continued up to the 7th hour and then decreased; 2) the half-life of p70 was shortened after 6 h after the stimulation; 3) p70 was localized in the nuclear fraction; 4) p70 was likely to be a primarily induced protein; 5) mRNA of p70 was supposed to be synthesized exclusively within 2 h of growth stimulation. These and the previous results suggest that p70 is a nuclear protein responsible for the early stage of transition of cells from the G0 toward the S phase and is induced via a different signal transduction sequence from that for the c-fos gene.
Takasuka
T
T
Department of Physiological Chemistry, Hiroshima University School of Medicine, Japan.
Sakayama
M
M
Ishibashi
S
S
Ide
T
T
D000818:Animals; D001790:Blood Physiological Phenomena; D002453:Cell Cycle / Q000235:genetics; D002455:Cell Division / Q000502:physiology*; D002460:Cell Line; D003609:Dactinomycin / Q000494:pharmacology; D015180:Electrophoresis, Gel, Two-Dimensional; D006207:Half-Life; D008970:Molecular Weight; D009154:Mutation; D009687:Nuclear Proteins / Q000096:biosynthesis*; D012333:RNA, Messenger / Q000096:biosynthesis; D013347:Subcellular Fractions / Q000032:analysis; D013696:Temperature
D009687:Nuclear Proteins; D012333:RNA, Messenger; D003609:Dactinomycin