Salzberg A, Cohen N, Halachmi N, Kimchie Z, Lev Z
Department of Biology, Technion-Israel Institute of Technology, Haifa.
Development. 1993 Apr;117(4):1309-19. doi: 10.1242/dev.117.4.1309.
The promoter of the Drosophila melanogaster Ras2 gene is bidirectional, regulating an additional gene oriented in the opposite polarity. The two divergently transcribed genes are only 93 bases apart and deletion analysis proved that common cis-acting elements within this promoter region are required for the transcriptional activity of both genes. We cloned the gene paired with Ras2 in the bidirectional promoter and isolated cDNAs corresponding to its mRNA. The Ras opposite (Rop) gene encodes for a 68 x 10(3) M(r) protein which shares sequence homology with the members of a novel Saccharomyces cerevisiae gene family, including the SLY1, SEC1 and VPS33 (SLP1) genes, all of which are involved in vesicle trafficking among yeast cellular compartments. A highly conserved motif in this family is also found in beta-COP, a coat protein isolated from rat Golgi-bound nonclathrin vesicles. Thus, the Rop protein may be a component of one of the vesicle trafficking pathways in Drosophila cells. The Rop gene expression during embryogenesis is restricted to the central nervous system (CNS) and the garland cells, a small group of nephrocytes that takes up waste materials from the haemolymph by endocytosis. Ras2 is also expressed in the embryonic garland cells. In postembryonic stages, the two genes are co-expressed in the larval salivary glands and the central nervous system, and in the adult CNS and reproductive systems. Interestingly, the S. cerevisiae SLY1-20 allele is a suppressor of the loss of the YPT1 gene, a ras-like gene implicated in vesicle translocation, suggesting that the two genes may interact with one another. Since Sec1p and beta-COP may also interact with small GTP-binding proteins of the ras superfamily, it is conceivable that the Rop and Ras2 gene products are not just co-expressed in common tissues, but may also functionally interact with one another in these tissues.
黑腹果蝇Ras2基因的启动子是双向的，调控着另一个极性相反的基因。这两个反向转录的基因仅相隔93个碱基，缺失分析证明该启动子区域内的共同顺式作用元件是这两个基因转录活性所必需的。我们克隆了双向启动子中与Ras2配对的基因，并分离出了与其mRNA对应的cDNA。Ras反向（Rop）基因编码一种68×10³ M（r）的蛋白质，它与一个新的酿酒酵母基因家族的成员具有序列同源性，包括SLY1、SEC1和VPS33（SLP1）基因，所有这些基因都参与酵母细胞区室间的囊泡运输。在从大鼠高尔基体结合的非网格蛋白囊泡中分离出的包被蛋白β-COP中也发现了该家族中的一个高度保守基序。因此，Rop蛋白可能是果蝇细胞中囊泡运输途径之一的一个组成部分。胚胎发育过程中Rop基因的表达仅限于中枢神经系统（CNS）和花环细胞，花环细胞是一小群肾细胞，通过内吞作用从血淋巴中摄取废物。Ras2也在胚胎花环细胞中表达。在胚胎后期阶段，这两个基因在幼虫唾液腺和中枢神经系统、成虫中枢神经系统和生殖系统中共同表达。有趣的是，酿酒酵母SLY1-20等位基因是YPT1基因缺失的抑制子，YPT1是一个与囊泡转运有关的类ras基因，这表明这两个基因可能相互作用。由于Sec1p和β-COP也可能与ras超家族的小GTP结合蛋白相互作用，可以想象Rop和Ras2基因产物不仅在共同组织中共表达，而且在这些组织中可能在功能上相互作用。
