SDC25, a New Gene of Saccharomyces Cerevisiae, Homologous to CDC25: The 3′-Part of SDC25 Encodes an Exchange Factor Able to Act on ras Proteins
Ras genes were first described as the transforming genes of the Kirsten and Harvey oncogenic retroviruses. They belong to a family of ubiquitous eucaryotic genes involved in growth control and in cell differentiation, ras gene products are GTP-binding proteins with an intrinsic GTPase activity. They activate their effector when bound to GTP but not when bound to GDP (Barbacid 1987). In Saccharomyces cerevisiae, the RAS1 and RAS2 genes are closely related to the ras genes of higher eucaryotic organisms (Dhar, Nieto et al. 1984; Powers, Kataoka et al. 1984) and their products activate adenylate cyclase encoded by the CYR1 gene (allelic to CDC35) (Broek, Samiy et al. 1985). As a result of this activation, cyclic AMP stimulates the cAMP-dependent protein kinase, whose regulatory subunit is encoded by the BCY1 gene (Toda, Cameron et al. 1987a). Three genes TPK1, TPK2 and TPK3 encode interchangeable catalytic subunits (Toda, Cameron et al. 1987b). The cAMP-dependent protein kinase pathway is essential for the cell division cycle since cAMP is required for the G1/S transition (Matsumoto, Uno et al. 1983a). This pathway relays also nutritional information which controls different processes such as carbohydrate storage (Martegani, Vanoni et al. 1986), sporulation (Iida and Yahara 1984) and a G1/G0 switch (Boy-Marcotte, Garreau et al. 1987).
KeywordsSaccharomyces Cerevisiae Adenylate Cyclase Multicopy Plasmid CDC25 Gene Intrinsic GTPase Activity
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