Shackleford G M, Varmus H E
Department of Microbiology and Immunology, University of California, San Francisco 94143.
Proc Natl Acad Sci U S A. 1988 Dec;85(24):9655-9. doi: 10.1073/pnas.85.24.9655.
Molecular genetic studies of mouse mammary tumor virus (MMTV) have been hampered by the difficulty of cloning proviruses of milk-borne strains because of inhibitory sequences located in the gag gene. To surmount this barrier we have constructed a hybrid MMTV provirus composed of clonable 5' sequences (encompassing gag) from an endogenous MMTV provirus of C3H mice (Mtv-1) and 3' sequences from the milk-borne strain of MMTV in C3H mice, MMTV(C3H). Virions produced from XC cells transfected with this hybrid provirus are infectious in cell culture and tumorigenic in BALB/cJ mice. A vector derived from this provirus, containing the neomycin phosphotransferase gene (neo) and origins of replication from simian virus 40 and pBR322, is capable of transferring G418 resistance by virus infection in cell culture when supplied with viral proteins from either MMTV(C3H) or the hybrid MMTV. Expression of both hybrid and vector proviruses is inducible by dexamethasone in infected cells.
由于位于gag基因中的抑制序列，克隆乳源性毒株的前病毒存在困难，这阻碍了对小鼠乳腺肿瘤病毒（MMTV）的分子遗传学研究。为了克服这一障碍，我们构建了一种杂交MMTV前病毒，它由C3H小鼠内源性MMTV前病毒（Mtv-1）的可克隆5'序列（包括gag）和C3H小鼠乳源性MMTV毒株MMTV（C3H）的3'序列组成。用这种杂交前病毒转染XC细胞产生的病毒粒子在细胞培养中具有感染性，在BALB/cJ小鼠中具有致瘤性。源自该前病毒的载体，含有新霉素磷酸转移酶基因（neo）以及猿猴病毒40和pBR322的复制起点，当从MMTV（C3H）或杂交MMTV提供病毒蛋白时，能够通过细胞培养中的病毒感染传递G418抗性。杂交前病毒和载体前病毒在受感染细胞中均可被地塞米松诱导表达。
