Burton W G, Roberts R J, Myers P A, Sager R
Proc Natl Acad Sci U S A. 1977 Jul;74(7):2687-91. doi: 10.1073/pnas.74.7.2687.
We have found a unique deoxyribonuclease in extracts of the eukaryotic green alga Chlamydomonas. When incubated with viral DNA from adenovirus-2, this enzyme produces discrete fragments that form bands upon electrophoresis in an agarose gel. Site specificity of the enzymatic cleavage examined by identifying the 5'-terminal nucleotides in cleaved adenovirus-2 DNA and by studies with synthetic polynucleotides of defined sequence, indicates that the initial endonucleolytic cleavage occurs at a site containing a deoxythymidine residue. Electron microscopy of cleaved adenovirus-2 DNA revealed single-strand segments within duplex DNA. We propose that the enzyme acts by making initial site-specific single-strand incisions, followed by subsequent excision on the same strand, producing a gapped duplex molecule; and that double-strand scissions result from limited occurrence of overlapping single-strand gaps on complementary strands.
我们在真核绿藻衣藻的提取物中发现了一种独特的脱氧核糖核酸酶。当与腺病毒2的病毒DNA一起孵育时，这种酶会产生离散的片段，这些片段在琼脂糖凝胶电泳时形成条带。通过鉴定切割后的腺病毒2 DNA中的5'-末端核苷酸以及对特定序列的合成多核苷酸进行研究来检测酶切的位点特异性，结果表明最初的核酸内切酶切割发生在含有脱氧胸苷残基的位点。对切割后的腺病毒2 DNA进行电子显微镜观察，发现双链DNA内有单链片段。我们认为该酶的作用方式是先进行位点特异性的单链切口，随后在同一条链上进行后续切除，产生一个有缺口的双链分子；而双链断裂则是由于互补链上有限的重叠单链缺口的出现所致。
