Sor F, Fukuhara H
Cell. 1983 Feb;32(2):391-6. doi: 10.1016/0092-8674(83)90458-0.
In the rho- mutants of yeast, the mitochondrial genome is made up of a small segment excised from the wild-type mitochondrial DNA. The segment is repeated either in tandem or in palindrome to form a series of multimeric DNAs. We have asked how the palindromic organization arises. From several palindromic rho- mitochondrial DNAs, we have isolated the restriction fragments that contained the head-to-head or tail-to-tail junction of the repeating units, and have determined their nucleotide sequences. We found that the palindromes were not symmetrical right up to the junction points: at the junction, there was always an asymmetrical sequence of variable length. At both ends of this junction sequence, we found inverted oligonucleotide sequences that were variable in each mutant and that were present in the wild-type DNA. At the moment of excision, a single-strand cut seems to occur at each of these short inverted repeats, in such a way that the two complementary strands of the genome are cut unequally and the single-stranded overhangs become the junction sequences between the palindromic repeating units. This scheme may account for the complex structures of many rho- mitochondrial DNAs.
在酵母的rho-突变体中，线粒体基因组由从野生型线粒体DNA切除的一小段组成。该片段以串联或回文形式重复，形成一系列多聚体DNA。我们研究了回文结构是如何产生的。从几个回文rho-线粒体DNA中，我们分离出了包含重复单元头对头或尾对尾连接的限制性片段，并确定了它们的核苷酸序列。我们发现，回文结构直到连接点都不是对称的：在连接点处，总是有一个长度可变的不对称序列。在这个连接序列的两端，我们发现了反向寡核苷酸序列，每个突变体中的这些序列都是可变的，并且存在于野生型DNA中。在切除时，似乎在每个这些短反向重复序列处发生单链切割，使得基因组的两条互补链被不等地切割，单链突出端成为回文重复单元之间的连接序列。这个方案可能解释了许多rho-线粒体DNA的复杂结构。
