Dinouël N, Drissi R, Miyakawa I, Sor F, Rousset S, Fukuhara H
Section de Biologie, Institut Curie, Centre Universitaire Paris XI, Orsay, France.
Mol Cell Biol. 1993 Apr;13(4):2315-23. doi: 10.1128/mcb.13.4.2315-2323.1993.
The terminal structure of the linear mitochondrial DNA (mtDNA) from three yeast species has been examined. By enzymatic digestion, alkali denaturation, and sequencing of cloned termini, it was shown that in Pichia pijperi and P. jadinii, both termini of the linear mtDNA were made of a single-stranded loop covalently joining the two strands, as in the case of vaccinia virus DNA. The left and right loop sequences were in either of two orientations, suggesting the existence of a flip-flop inversion mechanism. Contiguous to the terminal loops, inverted terminal repeats were present. The mtDNA from Williopsis mrakii seems to have an analogous structure, although terminal loops could not be directly demonstrated. Electron microscopy revealed the presence, among linear molecules, of a small number of circular DNAs, mostly of monomer length. Linear and circular models of replication are considered, and possible conversion mechanisms between linear and circular forms are discussed. A flip-flop inversion mechanism between the inverted repeat sequences within a circular intermediate may be involved in the generation of the linear form of mtDNA.
对三种酵母的线性线粒体DNA（mtDNA）的末端结构进行了研究。通过酶切、碱变性以及对克隆末端的测序，结果表明，在皮氏毕赤酵母和贾氏毕赤酵母中，线性mtDNA的两个末端均由共价连接两条链的单链环组成，就像痘苗病毒DNA那样。左右环序列存在两种方向，这表明存在一种翻转倒置机制。与末端环相邻的是反向末端重复序列。虽然不能直接证明末端环的存在，但嗜球果伞酵母的mtDNA似乎具有类似的结构。电子显微镜显示，在线性分子中存在少量的环状DNA，大多为单体长度。文中考虑了线性和环状复制模型，并讨论了线性和环状形式之间可能的转换机制。环状中间体中反向重复序列之间的翻转倒置机制可能参与了mtDNA线性形式的产生。
