Arnberg A C, Van Ommen G J, Grivell L A, Van Bruggen E F, Borst P
Cell. 1980 Feb;19(2):313-9. doi: 10.1016/0092-8674(80)90505-x.
11S and 18S fractions of yeast mitochondrial RNAs, isolated by electrophoresis through agarose gels, have been found by electron microscopy to contain approximately 50% circular molecules. Circles in the 11S fraction have a contour length of 0.36 +/- 0.02 micron, which is approximately equal to the length of the majority of linear molecules also present. Circles in the 18S fraction have an average length of 0.78 +/- 0.11 micron. The size distribution is broader than for the 11S fraction, and we cannot exclude the possibility that more than one size class may be present. The 11S circular RNA forms circular R loops and RNA-DNA hybrids with DNA fragments of the oxi 3 region of mtDNA, which contains the structural gene for subunit 1 of cytochrome oxidase. As judged from the electron micrographs, the complete RNA participates in hybrid formation and the sequences coding for it appear to be continuous. Both 11S and 18S circles withstand treatment with DNAase and pronase. They are not eliminated by treatment with 1 M glyoxal in 50% formamide for 1 hr at 50 degrees C. We conclude that they are covalently closed. The function of the circular RNAs is unknown. They may be active as mRNAs, storage forms, or arise in a cut-and-splice process which generates mRNAs from longer transcripts.
通过琼脂糖凝胶电泳分离得到的酵母线粒体RNA的11S和18S组分，经电子显微镜观察发现约含50%的环状分子。11S组分中的环的轮廓长度为0.36±0.02微米，这大约等于同时存在的大多数线性分子的长度。18S组分中的环平均长度为0.78±0.11微米。其大小分布比11S组分更宽，我们不能排除可能存在不止一种大小类别的可能性。11S环状RNA与线粒体DNA（mtDNA）oxi 3区域的DNA片段形成环状R环和RNA-DNA杂交体，该区域包含细胞色素氧化酶亚基1的结构基因。从电子显微镜照片判断，完整的RNA参与杂交体形成，其编码序列似乎是连续的。11S和18S环都能抵抗DNA酶和链霉蛋白酶的处理。在50℃用1M乙二醛在50%甲酰胺中处理1小时，它们不会被消除。我们得出结论，它们是共价封闭的。环状RNA的功能尚不清楚。它们可能作为mRNA具有活性，或是储存形式，或者产生于从较长转录本生成mRNA的剪切和拼接过程。
