Reymond C D, Gomer R H, Nellen W, Theibert A, Devreotes P, Firtel R A
Nature. 1986;323(6086):340-3. doi: 10.1038/323340a0.
The ras proto-oncogene, found in all eukaryotes so far examined, encode s a protein with guanine nucleotide-binding and GTPase activity. Gene disruption experiments in yeast indicate that ras is essential for cell growth. Anit-sense mutagenesis approaches suggest that this is also true for Dictyostelium. Most mutations causing an amino-acid substitution for Gly 12 result in decreased GTPase activity and produce a transforming phenotype. In yeast, a Gly 19---- Val 19, missense mutation (Gly 19 is similar to Gly 12 in mammalian and Dictyostelium ras proteins) causes a series of dominant phenotypes, including elevated adenylate cyclase activity. In mammalian cells there is no evidence that ras activates adenylate cyclase activity. D. discoideum contains a single ras gene (Dd-ras) that encodes a protein very similar to the mammalian ras protein and identical to c-ras at the potentially transforming positions. Dd-ras is expressed in vegetative cells and later in development in prestalk cells whereas ras protein is found in vegetative and developing cells. In the migrating pseudoplasmodium, ras protein is found in prestalk but not prespore cells, suggesting it is involved in the function and/or differentiation of the anteriorly localized prestalk cells. In this report we examine the effects of expression of a Dd-ras gene carrying a Gly-12----Thr 12 missense mutation.
原癌基因ras存在于迄今所检测的所有真核生物中，它编码一种具有鸟嘌呤核苷酸结合和GTP酶活性的蛋白质。酵母中的基因破坏实验表明，ras对细胞生长至关重要。反义诱变方法表明，盘基网柄菌也是如此。大多数导致甘氨酸12被氨基酸取代的突变会导致GTP酶活性降低，并产生转化表型。在酵母中，甘氨酸19突变为缬氨酸19的错义突变（甘氨酸19在哺乳动物和盘基网柄菌ras蛋白中与甘氨酸12相似）会导致一系列显性表型，包括腺苷酸环化酶活性升高。在哺乳动物细胞中，没有证据表明ras激活腺苷酸环化酶活性。盘基网柄菌含有一个单一的ras基因（Dd-ras），该基因编码一种与哺乳动物ras蛋白非常相似的蛋白质，并且在潜在的转化位置与c-ras相同。Dd-ras在营养细胞中表达，随后在发育过程中的柄细胞前体细胞中表达，而ras蛋白则存在于营养细胞和发育中的细胞中。在迁移的伪原质团中，ras蛋白存在于柄细胞前体细胞中而不存在于孢子细胞前体细胞中，这表明它参与了位于前部的柄细胞前体细胞的功能和/或分化。在本报告中，我们研究了携带甘氨酸12突变为苏氨酸12错义突变的Dd-ras基因表达的影响。
