Wang D, Liebowitz D, Kieff E
Kovler Viral Oncology Laboratory, University of Chicago, Illinois 60637.
J Virol. 1988 Jul;62(7):2337-46. doi: 10.1128/JVI.62.7.2337-2346.1988.
The gene encoding the Epstein-Barr virus membrane protein LMP, expressed in latent infection, is known to induce morphologic changes and some loss of contact inhibition in NIH 3T3 cells as well as profound loss of contact inhibition and of anchorage dependence in Rat-1 cells. Another form of LMP (D1LMP), deleted for the amino terminus and first four putative transmembrane domains of LMP, was recently shown to be expressed late in Epstein-Barr virus replication. We now demonstrate that D1LMP has no transformation-associated phenotypic effect in Rat-1 cells and does not significantly affect LMP-induced Rat-1 cell transformation. LMP activity and D1LMP inactivity in inducing anchorage-independent growth are not restricted to Rat-1 cells, but are also evident in BALB/c 3T3 cells. In both cell types, loss of contact inhibition and anchorage independence are acutely evident after LMP expression. Although newly transfected polyclonal Rat-1 or BALB/c cells have a lower agar cloning efficiency than established LMP-expressing clones, this is attributable, at least in part, to their lower average LMP expression, since among clones of transfected cells, higher cloning efficiencies correlated with higher levels of LMP. LMP is bound to the vimentin cytoskeletal network in rodent fibroblasts as it is in transformed lymphocytes, whereas D1LMP showed no detectable cytoskeletal binding, suggesting that cytoskeletal association may be integral to LMP-mediated cell transformation. LMP association with the cytoskeleton in latently infected, growth-transformed lymphocytes and LMP-transformed rodent fibroblasts, correlated with the lack of both rodent cell-transforming activity and cytoskeletal association of D1LMP supports working hypothesis that cytoskeletal association is important in LMP transforming activity.
编码爱泼斯坦-巴尔病毒膜蛋白LMP的基因在潜伏感染中表达，已知其可诱导NIH 3T3细胞发生形态变化并部分丧失接触抑制，同时导致大鼠-1细胞完全丧失接触抑制和锚定依赖性。LMP的另一种形式（D1LMP）缺失了LMP的氨基末端和前四个假定的跨膜结构域，最近发现其在爱泼斯坦-巴尔病毒复制后期表达。我们现在证明，D1LMP在大鼠-1细胞中没有转化相关的表型效应，并且对LMP诱导的大鼠-1细胞转化没有显著影响。LMP诱导非锚定依赖性生长的活性和D1LMP的无活性不仅限于大鼠-1细胞，在BALB/c 3T3细胞中也很明显。在这两种细胞类型中，LMP表达后接触抑制和非锚定依赖性的丧失都很明显。尽管新转染的多克隆大鼠-1或BALB/c细胞的琼脂克隆效率低于已建立的LMP表达克隆，但这至少部分归因于它们较低的平均LMP表达，因为在转染细胞的克隆中，较高的克隆效率与较高水平的LMP相关。LMP与啮齿动物成纤维细胞中的波形蛋白细胞骨架网络结合，就像在转化的淋巴细胞中一样，而D1LMP没有可检测到的细胞骨架结合，这表明细胞骨架关联可能是LMP介导的细胞转化所必需的。LMP与潜伏感染、生长转化的淋巴细胞和LMP转化的啮齿动物成纤维细胞中的细胞骨架关联，与D1LMP缺乏啮齿动物细胞转化活性和细胞骨架关联相关，支持了细胞骨架关联在LMP转化活性中很重要的工作假设。
