Etkind P R, Szabo P, Sarkar N H
J Virol. 1982 Mar;41(3):855-67. doi: 10.1128/JVI.41.3.855-867.1982.
Cellular DNA containing integrated murine mammary tumor virus (MuMTV) was isolated from FeI/C6 feline kidney cells and CCL64 mink lung cells infected with milkborne RIII MuMTV. By using restriction enzyme HpaI, intact RIII MuMTV provirus (length, 8.7 kilobases [kb]) was excised from the cellular DNA. Subsequent restriction endonuclease analysis of this HpaI fragment with KpnI, HindIII, EcoRI, BamHI, BglII, PstI, SstI, SalI, and XhoI enabled us to construct a map of the RIII virus genome. A comparison of this map with the maps of the GR and C3H MuMTV's revealed that there are greater sequence differences between the RIII virus and the GR and C3H MuMTV proviruses than there are between the GR and C3H proviruses. The following are features of the restriction map unique to the RIII provirus: the presence of three BamHI and two EcoRI cleavage sites, a HpaI cleavage site in the terminal 3'-5' repeat unit of the provirus, and the absence of an XhoI cleavage site. Another distinguishing feature of the RIII provirus is that the sizes of some of the restriction fragments produced by cleavage of the RIII provirus with PstI are different from the sizes of the fragments obtained by PstI cleavage of the GR and C3H proviruses. Like the GR proviral DNA, the RIII proviral DNA has three SstI (SacI) cleavage sites, whereas the C3H provirus has only two SstI sites. HpaI digestion of MuMTV-infected mink lung cell DNA revealed only one class of provirus (an 8.7-kb fragment); however, we observed several minor classes of RIII proviral DNA in addition to the major class of provirus DNA in infected cat kidney cells. PstI digestion of the HpaI 8.7-kb fragments from both feline and mink cells generated a 3.7-kb DNA fragment identical in size to a PstI-generated fragment that has been found in GR and C3H milkborne virus-infected cells. Although a fragment similar in size to the milkborne 3.7-kb PstI fragment has been found as an endogenous component in many C3H and GR mouse tissues, we did not observe such an endogenous fragment in the RIII mouse strain. Therefore, the 3.7-kb fragment may be useful as a marker for the milkborne RIII MuMTV provirus in RIII mice.
从感染了经乳汁传播的RIII型小鼠乳腺肿瘤病毒（MuMTV）的FeI/C6猫肾细胞和CCL64貂肺细胞中分离出含有整合型鼠乳腺肿瘤病毒的细胞DNA。使用限制性内切酶HpaI，从细胞DNA中切下完整的RIII型MuMTV前病毒（长度为8.7千碱基[kb]）。随后用KpnI、HindIII、EcoRI、BamHI、BglII、PstI、SstI、SalI和XhoI对该HpaI片段进行限制性内切酶分析，使我们能够构建RIII病毒基因组图谱。将该图谱与GR和C3H型MuMTV的图谱进行比较，发现RIII病毒与GR和C3H型MuMTV前病毒之间的序列差异大于GR和C3H型前病毒之间的差异。以下是RIII前病毒限制性图谱独有的特征：存在三个BamHI和两个EcoRI切割位点，在前病毒末端3'-5'重复单元中有一个HpaI切割位点，并且不存在XhoI切割位点。RIII前病毒的另一个显著特征是，用PstI切割RIII前病毒产生的一些限制性片段的大小与用PstI切割GR和C3H型前病毒获得的片段大小不同。与GR前病毒DNA一样，RIII前病毒DNA有三个SstI（SacI）切割位点，而C3H前病毒只有两个SstI位点。用HpaI消化感染MuMTV的貂肺细胞DNA只揭示了一类前病毒（一个8.7-kb片段）；然而，我们在感染的猫肾细胞中除了主要的前病毒DNA类别外，还观察到了几类次要的RIII前病毒DNA。用PstI消化来自猫和貂细胞的HpaI 8.7-kb片段，产生了一个3.7-kb的DNA片段，其大小与在GR和C3H型经乳汁传播的病毒感染细胞中发现的PstI产生的片段相同。尽管在许多C3H和GR小鼠组织中已发现大小与经乳汁传播的3.7-kb PstI片段相似的片段作为内源性成分，但我们在RIII小鼠品系中未观察到这样的内源性片段。因此，3.7-kb片段可能作为RIII小鼠中经乳汁传播的RIII型MuMTV前病毒的标记物。
