Landy-Otsuka F, Scheffler I E
J Cell Physiol. 1980 Nov;105(2):209-20. doi: 10.1002/jcp.1041050204.
A temperature-sensitive (ts) cell cycle mutant of Chinese hamster fibroblasts with a block in G1 was investigated. Attention was on the expression of the activity of three enzymes: ornithine decarboxylase (ODC) S-adenosylmethionine decarboxylase (SAMDC), and thymidine kinase (TK). ODC and SAMDC activities are normally induced in the middle of, or late in, the G1 phase, while TK activity starts to appear at the G1/S boundary. In the ts mutant released from serum starvation at the nonpermissive temperature (40.8 degrees C), we find no effect on the expression of SAMDC activity, a significantly reduced level of ODC activity compared to the control at the permissive temperature (34 degrees C), and no induction of TK activity. Results presented here and in a previous publication (Landy-Otsuka and Scheffler, '78) suggest that the decrease in ODC activity is due to an effect of the nonpermissive temperature on a post-transcriptional step, possibly a very rapid inactivation of the enzyme. The absence of TK activity, on the other hand, appears to be due to a block in transcription at the nonpermissive temperature.
对中国仓鼠成纤维细胞的一种温度敏感（ts）细胞周期突变体进行了研究，该突变体在G1期受阻。研究重点是三种酶的活性表达：鸟氨酸脱羧酶（ODC）、S-腺苷甲硫氨酸脱羧酶（SAMDC）和胸苷激酶（TK）。ODC和SAMDC的活性通常在G1期中期或后期被诱导，而TK活性在G1/S边界开始出现。在非允许温度（40.8摄氏度）下从血清饥饿中释放的ts突变体中，我们发现对SAMDC活性的表达没有影响，与允许温度（34摄氏度）下的对照相比，ODC活性水平显著降低，并且没有诱导TK活性。此处呈现的结果以及之前一篇出版物（Landy - Otsuka和Scheffler，'78）中的结果表明，ODC活性的降低是由于非允许温度对转录后步骤的影响，可能是该酶的非常快速的失活。另一方面，TK活性的缺失似乎是由于在非允许温度下转录受阻。
