Tooze J, Tooze S, Haisma H, Hilgers J
Eur J Cell Biol. 1985 Nov;39(1):224-31.
By electron microscopy and immunocytochemistry we have examined the retroviruses endogenous to AtT20 D16V cells, a cloned line of murine pituitary tumour cells. In addition to the C-type retrovirus particles related to Rauscher murine leukemia virus (MuLV) previously reported to bud from these cells we observed cytoplasmic A-type particles and intracisternal A-type particles (IAP). In the cytoplasm the A-type particles occur in large clusters often associated with sheets of material with a fine structure resembling the shells of the particles. At the plasma membrane individual A-type particles bud to give rise to extracellular virions. The IAP are restricted to the rough endoplasmic reticulum (RER) into which they bud: they are not transported out of the RER to the Golgi apparatus and beyond. We describe a new monoclonal antibody (designated 83E7) which is specific for an epitope of the major core protein (MTVp27) of mouse mammary tumour virus (MMTV). Using immunogold labelling procedures we have specifically labelled both the A-type particles and the associated sheets of material with this antibody. We conclude that the A-type particles and the virions they give rise to are MMTV. The sheets of material must also at least in part be made up of the major core protein of MMTV or its precursor polypeptide. AtT20 cells, therefore, contain endogenous MuLV and MMTV as well as IAP.
通过电子显微镜和免疫细胞化学技术，我们检测了AtT20 D16V细胞（一种克隆的小鼠垂体肿瘤细胞系）内源性逆转录病毒。除了先前报道的与劳氏鼠白血病病毒（MuLV）相关的C型逆转录病毒颗粒从这些细胞中出芽外，我们还观察到了胞质A型颗粒和内质网A型颗粒（IAP）。在细胞质中，A型颗粒以大簇形式出现，常常与具有类似于颗粒外壳精细结构的物质片层相关联。在质膜处，单个A型颗粒出芽形成细胞外病毒粒子。IAP局限于糙面内质网（RER），并在其中出芽：它们不会从RER转运到高尔基体及更远的地方。我们描述了一种新的单克隆抗体（命名为83E7），它对小鼠乳腺肿瘤病毒（MMTV）的主要核心蛋白（MTVp27）的一个表位具有特异性。使用免疫金标记程序，我们用这种抗体特异性标记了A型颗粒和相关的物质片层。我们得出结论，A型颗粒及其产生的病毒粒子是MMTV。这些物质片层至少部分也必须由MMTV的主要核心蛋白或其前体多肽组成。因此，AtT20细胞含有内源性MuLV、MMTV以及IAP。
