Griffin B E, Fried M, Cowie A
Proc Natl Acad Sci U S A. 1974 May;71(5):2077-81. doi: 10.1073/pnas.71.5.2077.
The action of restriction enzymes on polyoma DNA was studied with uniformly (32)P-labeled viral DNA obtained from either infected 3T6 or secondary mouse-embryo cells. Three restriction enzymes were used to construct a physical map of the polyoma genome. An enzyme from Hemophilus parainfluenzae, Hpa(II), cleaved polyma DNA into eight unique fragments (Hpa(II)-1 to Hpa(II)-8), ranging in size from 27.3 to 1.8% of the genome. An enzyme from Hemophilus influenzae, Hin(III), gave two fragments (56 and 44%); and a third enzyme from Escherichia coli, EcoR(I), cut at a single unique site. The physical map of the polyma genome was constructed from methods involving: (1) further digestion of the fragments produced by enzymes EcoR(I) and Hin(III) with Hpa(II), and (2) analysis of the products of partial digestion with Hpa(II). Analysis by electron microscopy of replicating DNA molecules (less than 50% replicated) cut with the Hin(III) enzyme, in combination with other studies, has indicated that the origin of DNA replication is located at 71 +/- 3 map units from the EcoR(I) cleavage site, probably in Hpa(II)-5.
利用从感染的3T6细胞或二代小鼠胚胎细胞中获得的均匀（32）P标记的病毒DNA，研究了限制性内切酶对多瘤病毒DNA的作用。使用三种限制性内切酶构建了多瘤病毒基因组的物理图谱。来自副流感嗜血杆菌的一种酶Hpa（II）将多瘤病毒DNA切割成八个独特的片段（Hpa（II）-1至Hpa（II）-8），大小范围从基因组的27.3%到1.8%。来自流感嗜血杆菌的一种酶Hin（III）产生两个片段（分别为56%和44%）；来自大肠杆菌的第三种酶EcoR（I）在一个独特的位点切割。多瘤病毒基因组的物理图谱是通过以下方法构建的：（1）用Hpa（II）对EcoR（I）和Hin（III）酶产生的片段进行进一步消化，以及（2）分析Hpa（II）部分消化的产物。用Hin（III）酶切割的复制DNA分子（复制少于50%）的电子显微镜分析，结合其他研究表明，DNA复制起点位于距EcoR（I）切割位点71±3个图谱单位处，可能在Hpa（II）-5片段中。
