Morrissey D, Askew D, Raj L, Weir M
Department of Biology, Wesleyan University, Middletown, Connecticut 06459.
Genes Dev. 1991 Sep;5(9):1684-96. doi: 10.1101/gad.5.9.1684.
An ectopic expression assay in Drosophila embryos was used to investigate the roles of pair-rule segmentation genes in the spatial regulation of the segment-polarity gene, engrailed (en). It is hypothesized that the regions of overlap in expression of two genes, paired (prd) and even-skipped (eve), define the odd-numbered en expression stripes. Consistent with this combinatorial model, ectopic expression of prd caused these en stripes to be expanded posteriorly. Surprisingly, however, ectopic expression of a prd gene with a deletion of the conserved paired box resulted in loss of these odd-numbered en stripes. This dominant negative effect is a phenocopy of en expression in prd embryos and suggests that the paired box is necessary for normal prd- function. A similar deletion of odd-numbered en stripes was also observed after ectopic expression of a chimeric fushi tarazu (ftz) gene containing a substituted prd gene homeo box; in addition, in these embryos, the even-numbered en stripes were expanded anteriorly, as observed when the unaltered ftz gene is ectopically expressed. These effects suggest that the chimeric protein may have DNA or protein targets of both the normal Ftz and Prd proteins.
利用果蝇胚胎中的异位表达试验来研究成对规则分割基因在节段极性基因engrailed（en）空间调控中的作用。据推测，成对（prd）和偶数跳格（eve）这两个基因表达的重叠区域决定了奇数编号的en表达条纹。与这种组合模型一致，prd的异位表达导致这些en条纹向后扩展。然而，令人惊讶的是，缺失保守成对结构域的prd基因的异位表达导致这些奇数编号的en条纹消失。这种显性负效应是prd胚胎中en表达的拟表型，表明成对结构域对于正常的prd功能是必需的。在异位表达含有替代prd基因同源框的嵌合分节基因（ftz）后，也观察到奇数编号的en条纹有类似缺失；此外，在这些胚胎中，偶数编号的en条纹向前扩展，这与未改变的ftz基因异位表达时观察到的情况一样。这些效应表明，嵌合蛋白可能具有正常Ftz和Prd蛋白的DNA或蛋白质靶点。
