Thinakaran G, Bag J
Department of Molecular Biology and Genetics, University of Guelph, ON, Canada.
Biochem Cell Biol. 1993 May-Jun;71(5-6):260-9. doi: 10.1139/o93-040.
Skeletal myoblasts undergo terminal differentiation when maintained under low-mitogen conditions. We have examined the expression of c-jun, one of the growth-factor-inducible immediate-early genes, during myogenic differentiation of L6 myoblasts. The steady-state levels of c-jun mRNA, c-Jun polypeptide, and activator protein 1 binding activity were not markedly altered in L6 cells undergoing myogenic differentiation. Although expression of c-jun is induced by serum mitogens in fibroblasts and other cell lines, addition of high serum to proliferating myoblasts resulted in the activation of another immediate early gene junB, but not c-jun mRNA expression. These results indicate that regulation of c-jun may differ from that of other immediate early genes in L6 cells. Manipulation of myogenesis by exposing L6 cells to dimethyl sulfoxide also suggested that expression of myogenin and muscle differentiation could occur in the presence of high levels of c-Jun. Furthermore, expression of c-jun from Moloney murine leukaemia viral long-terminal repeat in transfected L6 cells confirmed that constitutive expression of c-jun does not interfere with myogenesis in L6 myoblasts. Therefore, regulation of c-jun expression in rat L6 cells differs from that in the mouse C2 cell line.
骨骼肌成肌细胞在低丝裂原条件下维持时会经历终末分化。我们检测了生长因子诱导的即刻早期基因之一c-jun在L6成肌细胞成肌分化过程中的表达。在经历成肌分化的L6细胞中，c-jun mRNA、c-Jun多肽的稳态水平以及激活蛋白1结合活性均未发生明显改变。虽然在成纤维细胞和其他细胞系中，c-jun的表达由血清丝裂原诱导，但向增殖的成肌细胞中添加高血清会导致另一个即刻早期基因junB的激活，而不是c-jun mRNA的表达。这些结果表明，L6细胞中c-jun的调控可能与其他即刻早期基因不同。通过将L6细胞暴露于二甲基亚砜来操纵肌生成也表明，在高水平c-Jun存在的情况下，肌细胞生成素的表达和肌肉分化可能会发生。此外，在转染的L6细胞中，莫洛尼鼠白血病病毒长末端重复序列驱动的c-jun表达证实，c-jun的组成型表达不会干扰L6成肌细胞的肌生成。因此，大鼠L6细胞中c-jun表达的调控与小鼠C2细胞系不同。
