Petersen N S, Lankenau D H, Mitchell H K, Young P, Corces V G
Department of Molecular Biology, University of Wyoming, Laramie 82071.
Genetics. 1994 Jan;136(1):173-82. doi: 10.1093/genetics/136.1.173.
The forked (f) gene of Drosophila melanogaster encodes six different transcripts 6.4, 5.6, 5.4, 2.5, 1.9, and 1.1 kb long. These transcripts arise by the use of alternative promoters. A polyclonal antibody raised against a domain common to all of the forked-encoded products has been used to identify forked proteins on two-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis gels and in Drosophila pupal tissues. The antibody stains fiber bundles present in bristle cells for about 15 hr during normal pupal development. Electron microscopy shows that these fibers are present from 40 to 53 hr in bristles of wild-type flies but are absent in the null f36a mutant. The forked protein(s) thus appear to be an essential part of the bristle fibers. The phenotype of the f36a mutation can be rescued by a 13-kb fragment of the forked locus containing the coding regions for the 2.5, 1.9, and 1.1-kb transcripts, suggesting that the proteins encoded by the three large forked RNAs are dispensable during bristle development. Increasing the copy number of a P[w+,f+] construct containing the 13-kb fragment induces a hypermorphic bristle phenotype whose severity correlates with the number of copies of P[w+,f+] present. These results indicate that alterations in the ratios among the forked proteins, or between forked products and other components of the fiber, result in abnormal assembly of the fibrillar cytoplasmic structures necessary for bristle morphogenesis.
黑腹果蝇的叉状（f）基因编码六种不同的转录本，长度分别为6.4、5.6、5.4、2.5、1.9和1.1千碱基对。这些转录本通过使用替代启动子产生。一种针对叉状编码产物共有的结构域产生的多克隆抗体，已被用于在二维十二烷基硫酸钠-聚丙烯酰胺凝胶电泳凝胶上以及果蝇蛹组织中鉴定叉状蛋白。在正常蛹发育过程中，该抗体对刚毛细胞中存在的纤维束染色约15小时。电子显微镜显示，这些纤维在野生型果蝇的刚毛中从40小时到53小时存在，但在无效的f36a突变体中不存在。因此，叉状蛋白似乎是刚毛纤维的重要组成部分。f36a突变的表型可以通过叉状基因座的一个13千碱基对的片段来挽救，该片段包含2.5、1.9和1.1千碱基对转录本的编码区，这表明由三个大的叉状RNA编码的蛋白质在刚毛发育过程中是可有可无的。增加包含13千碱基对片段的P[w +,f +]构建体的拷贝数会诱导一种超形态刚毛表型，其严重程度与存在的P[w +,f +]拷贝数相关。这些结果表明，叉状蛋白之间的比例变化，或叉状产物与纤维的其他成分之间的比例变化，会导致刚毛形态发生所需的纤维状细胞质结构异常组装。
