Ruben M M, Rudnicki M A, Bladon T S, Jardine K, Craig J, McBurney M W
Department of Medicine, University of Ottawa, Canada.
Biochim Biophys Acta. 1988 Sep 7;950(3):374-84. doi: 10.1016/0167-4781(88)90134-0.
The human cardiac-actin (CH-actin) gene was transfected into rat L6 skeletal myoblasts and stable transformants were isolated. The level of the CH-actin transcript varied between clones but changed little during the differentiation of myoblasts into multinucleate myotubes. Chimeric genes were constructed in which the CH-actin promoter, first non-coding exon (44 bp), and first intron (about 700 bp) were linked to the Herpes simplex virus thymidine kinase (tk) coding region. Clones of L6 cells transformed with these chimeric genes contained variable levels of actin-tk mRNA which changed little during differentiation. Thus, the activity of the CH-actin promoter appeared not to be up-regulated upon differentiation of myoblasts into myotubes. In clones of cells expressing the actin-tk mRNA, the TK protein was not detected in myoblasts but appeared in differentiating multinucleate myotubes. We interpret these results as suggesting developmentally regulated translation of the actin-tk mRNA. Since the first 44 nucleotides of the actin-tk mRNA were derived from the 5'-untranslated region of the CH-actin mRNA. These experiments suggest that translation of the actin-tk mRNA may be controlled by this region.
将人心脏肌动蛋白（CH-肌动蛋白）基因转染至大鼠L6骨骼肌成肌细胞，并分离出稳定的转化体。CH-肌动蛋白转录本的水平在各克隆之间有所不同，但在成肌细胞分化为多核肌管的过程中变化不大。构建了嵌合基因，其中CH-肌动蛋白启动子、首个非编码外显子（44 bp）和首个内含子（约700 bp）与单纯疱疹病毒胸苷激酶（tk）编码区相连。用这些嵌合基因转化的L6细胞克隆含有可变水平的肌动蛋白-tk mRNA，其在分化过程中变化不大。因此，CH-肌动蛋白启动子的活性在成肌细胞分化为肌管时似乎未被上调。在表达肌动蛋白-tk mRNA的细胞克隆中，在成肌细胞中未检测到TK蛋白，但在分化的多核肌管中出现。我们将这些结果解释为提示肌动蛋白-tk mRNA的翻译受发育调控。由于肌动蛋白-tk mRNA的前44个核苷酸来自CH-肌动蛋白mRNA的5'非翻译区。这些实验表明肌动蛋白-tk mRNA的翻译可能受该区域控制。
