Günzburg W H, Salmons B
Virology. 1986 Nov;155(1):236-48. doi: 10.1016/0042-6822(86)90183-2.
The mammary gland specific, glucocorticoid controlled expression of MMTV makes it an ideal candidate for the basis of a nonpromiscuous regulated retroviral vector system. We have previously constructed an MMTV proviral variant that gives rise to virus particles upon introduction into cultured cells. This was used to construct a defective MMTV provirus in which the MMTV env gene was replaced by the neomycin resistance gene under the control of the herpes simplex thymidine kinase promotor. The defective provirus was packaged after transfection into two distinct MMTV producing cell lines. Conditioned medium from these cells contains virus particles which are able to infect cells of fibroblast and epithelial origin and to confer neomycin resistance upon them. This indicates that the defective MMTV provirus contains the sequences required for packaging of the genomic viral RNA. Transfection of the same MMTV-neo recombinant provirus into the MoMLV packaging cell line, psi 2, did not result in any infectious virus particles. Thus the packaging signals for MMTV and MoMLV appear to be distinct. Analysis of the MMTV infected cells reveals the presence of the MMTV-neo recombinant provirus. Expression of both MMTV and neomycin is detectable and augmented when the infected cells are grown in the presence of glucocorticoid hormone.
MMTV的乳腺特异性、糖皮质激素控制表达使其成为非混杂调控逆转录病毒载体系统基础的理想候选者。我们之前构建了一种MMTV前病毒变体，将其导入培养细胞后可产生病毒颗粒。这被用于构建一种缺陷型MMTV前病毒，其中MMTV env基因被置于单纯疱疹胸苷激酶启动子控制下的新霉素抗性基因所取代。将缺陷型前病毒转染到两种不同的MMTV产生细胞系后进行包装。这些细胞的条件培养基中含有能够感染成纤维细胞和上皮来源细胞并赋予它们新霉素抗性的病毒颗粒。这表明缺陷型MMTV前病毒包含基因组病毒RNA包装所需的序列。将相同的MMTV-neo重组前病毒转染到MoMLV包装细胞系psi 2中，未产生任何感染性病毒颗粒。因此，MMTV和MoMLV的包装信号似乎是不同的。对MMTV感染细胞的分析揭示了MMTV-neo重组前病毒的存在。当感染细胞在糖皮质激素存在下生长时，可检测到MMTV和新霉素的表达且表达增强。
