Pritchard M A, Dura J M, Pélisson A, Bucheton A, Finnegan D J
Department of Molecular Biology, University of Edinburgh, UK.
Mol Gen Genet. 1988 Nov;214(3):533-40. doi: 10.1007/BF00330491.
I-R hybrid dysgenesis in Drosophila melanogaster occurs in female progeny of crosses between reactive strain females and inducer strain males, and is controlled by transposable elements called I-factors. These are 5.4 kb elements that are structurally similar to mammalian LINE elements and other retroposons. We have tested the activity of an I-factor directly, by introducing it into the genome of a reactive strain, using P-element mediated transformation. It confers the complete inducer phenotype on the reactive strain, and can stimulate dysgenesis when transformed males are mated with reactive females. It has transposed in the transformed lines, and we have cloned one of the transposed copies. This is the first time that it has been possible to demonstrate that a particular retroposon is transposition proficient, and to compare donor and transposed elements. We propose a mechanism for I-factor transposition based on these results, and the coding capacity of these elements. We have been unable to detect either autonomous transposition of a complete I-factor from a plasmid injected into reactive strain embryos, or transposition of a marked I-factor when co-injected with a complete element.
黑腹果蝇中的I-R杂种不育现象发生在反应型品系雌性与诱导型品系雄性杂交产生的雌性后代中，并且受称为I因子的转座元件控制。这些元件长度为5.4 kb，在结构上与哺乳动物的长散在核元件（LINE元件）及其他反转录转座子相似。我们通过P因子介导的转化，将一个I因子导入反应型品系的基因组中，从而直接测试了该I因子的活性。它赋予反应型品系完整的诱导型表型，并且当转化后的雄性与反应型雌性交配时能够刺激杂种不育。它已在转化系中发生转座，我们克隆了其中一个转座拷贝。这是首次能够证明某个特定的反转录转座子具有转座能力，并对供体元件和转座后的元件进行比较。基于这些结果以及这些元件的编码能力，我们提出了一种I因子转座的机制。我们既未能检测到注入反应型品系胚胎的质粒中完整I因子的自主转座，也未检测到与完整元件共注射时标记I因子的转座。
