A nuclear labile protein, p70, is expressed exclusively during G0-S transition but not in G1 phase of a cell cycle ts mutant, tsJT16.
tsJT16 is a cell cycle temperature-sensitive (ts) mutant from a Fischer rat cell line. When it is growth-stimulated from G0 phase it enters S phase at the permissive temperature (34 degrees C) but not at the nonpermissive temperature (40 degrees C). It induces a nuclear labile protein, p70, when it is stimulated from G0 phase at 34 degrees C, but not at 40 degrees C. In growing cell cycle it progresses through the S, G2 and M phases at both temperatures but fails to pass through G1 phase at 40 degrees C. Here we described that p70 was synthesized neither in the randomly growing cycle nor in the G1 phase synchronously progressing from M phase. The cells synchronized at early G1 phase by culturing in serum-free medium for 7.5 h from G1/S boundary induced c-fos and c-myc following serum addition, but under the same condition p70 was not synthesized. These results indicate that the synthesis of p70 is not required for progression of the G1 phase of the growing cycle and can be used as an exclusive marker of G0-S transition.
Takasuka
T
T
Department of Cellular and Molecular Biology, Hiroshima University School of Medicine, Japan.
Sakayama
M
M
Miyake
E
E
Ishibashi
S
S
Ide
T
T
D000818:Animals; D015152:Blotting, Northern; D002460:Cell Line; D002472:Cell Transformation, Viral; D015180:Electrophoresis, Gel, Two-Dimensional; D016193:G1 Phase; D007399:Interphase; D008938:Mitosis; D009154:Mutation; D009687:Nuclear Proteins / Q000096:biosynthesis*; D051381:Rats; D016192:Resting Phase, Cell Cycle; D016196:S Phase; D013696:Temperature
D009687:Nuclear Proteins