Pont G, Degroote F, Picard G
Laboratoire de Génétique, Université Clermont-Fd. II, UA 360 CNRS, Aubière, France.
J Mol Biol. 1987 May 20;195(2):447-51. doi: 10.1016/0022-2836(87)90665-6.
In Drosophila melanogaster embryos we have identified three classes of extrachromosomal circular DNA molecules homologous to the three main families of tandemly repeated genes, 5 S, rDNA and histone. 5 S genes are present in circular multimeric molecules containing up to 16 copies of the 375(+/- 7) base-pair repeated unit. Circular molecules homologous to rDNA are also multimeric molecules, which contain up to ten copies of the 240 base-pair tandemly repeated sequence of the non-transcribed spacer. The two major genomic classes of histone units (4800 and 5000 bases) are found only as monomeric circular molecules. No circular intermediate of the I transposable element was detected in embryos laid by F1 dysgenic females produced by the I-R system of hybrid dysgenesis. As far as we know, it is the first time that genes have been identified among extrachromosomal circular molecules independently of any specific amplification phenomenon.
在黑腹果蝇胚胎中，我们已经鉴定出三类与串联重复基因的三个主要家族（5S、rDNA和组蛋白）同源的染色体外环状DNA分子。5S基因存在于环状多聚体分子中，这些分子包含多达16个375（±7）碱基对重复单元的拷贝。与rDNA同源的环状分子也是多聚体分子，其中包含多达十个240碱基对的非转录间隔区串联重复序列的拷贝。组蛋白单位的两个主要基因组类别（4800和5000个碱基）仅作为单体环状分子被发现。在由杂种不育的I-R系统产生的F1杂种不育雌性所产的胚胎中，未检测到I转座因子的环状中间体。据我们所知，这是首次在染色体外环状分子中独立于任何特定扩增现象鉴定出基因。
