Tsukamoto I, Wakabayashi M, Takebayashi K, Nomura S
Department of Food Science and Nutrition, Nara Women's University, Japan.
Biochim Biophys Acta. 1996 Aug 13;1290(3):267-72. doi: 10.1016/0304-4165(96)00029-3.
To elucidate the molecular basis for the periodic change of thymidine kinase (TK) activity, the expressions of TK protein and TK mRNA were examined during liver regeneration. TK protein level, quantified by immunoblotting assay using the polyclonal antiserum against rat TK polypeptide produced in Escherichia coli, increased 13-fold compared with the normal at 24 h after partial hepatectomy. This was closely correlated with a 11-fold increase in TK activity. Northern blot analysis showed that the partial hepatectomy caused 12- and 8-fold increase in 2.6 kb and 1.1 kb TK mRNA at 24 h after surgery, respectively. During next 12 h the levels of both TK mRNA species reduced to 5-fold of the normal base level. This reduction was coupled with a similar decrease in the activity as well as in the amount of TK protein. The TK mRNA levels were strictly proportional to the levels of TK activity and TK protein at 48 h and 72 h after partial hepatectomy. These results demonstrate that the change in TK activity is controlled at the mRNA level during liver regeneration. The injection of alpha-adrenoceptor antagonist, phenoxybenzamine, calcium channel blocker, nifedipine or calmodulin inhibitor, trifluoperazine was also found to inhibit TK activity by the repression of its mRNA level.
为阐明胸苷激酶（TK）活性周期性变化的分子基础，在肝脏再生过程中检测了TK蛋白和TK mRNA的表达。通过使用针对在大肠杆菌中产生的大鼠TK多肽的多克隆抗血清进行免疫印迹分析来定量TK蛋白水平，部分肝切除术后24小时，其水平与正常水平相比增加了13倍。这与TK活性增加11倍密切相关。Northern印迹分析表明，部分肝切除术后24小时，2.6 kb和1.1 kb的TK mRNA分别增加了12倍和8倍。在接下来的12小时内，两种TK mRNA的水平均降至正常基础水平的5倍。这种降低伴随着TK活性以及TK蛋白量的类似下降。部分肝切除术后48小时和72小时，TK mRNA水平与TK活性和TK蛋白水平严格成正比。这些结果表明，在肝脏再生过程中，TK活性的变化在mRNA水平受到控制。还发现注射α-肾上腺素能受体拮抗剂酚苄明、钙通道阻滞剂硝苯地平或钙调蛋白抑制剂三氟拉嗪可通过抑制其mRNA水平来抑制TK活性。
