Recent evidence from genetic studies in yeast raises the strong possibility that a new family of GTP-binding proteins related in size and sequence (30-40% homology) to the 21 kD mammalian ras oncogene family catalyzes steps in protein targeting and secretion. One member of this family in yeast (y-YPT) affects transport through the ER and Golgi when mutated. A mammalian gene 85% homologous to the yeast YPT gene has recently been cloned. We propose to test whether this gene's product (termed m-YPT; 'm' = mammalian) functions in secretion in animal cells. We propose to prepare antibodies to m-YPT expressed in E. coli, and to localize the protein in animal cells by immuno-electron microscopy. We also plan to make use of neutralizing monoclonal and polyclonal antibodies in combination with established mammalian cell-free and semi-intact cell systems that reconstitute steps in the secretory pathway to probe the function of m-YPT in secretion. We hope to use the m-YPT gene and it sequence to identify a novel family of ras-related """"""""sec"""""""" genes that may be needed for secretion in mammalian cells. Recent evidence suggests that a human ras oncogene product causes massive uncontrolled secretion in mast cells. This, together with the evidence from yeast, raises the intriguing possibility that the normal function of certain ras and ras-related proteins (currently unknown) may be in controlling secretory and other intracellular transport processes. The potential role of members of this putative ras-related """"""""sec"""""""" gene family as oncogenes will be tested by introducing mutations of a kind that are known to activate classical ras proto-oncogenes. The phenotypes of similar mutations in a new class of ras-related """"""""sec"""""""" genes may well reveal a whole new class of oncogenes associated with cancers. Thus work is likely to be of significance for cell biology, and may also afford novel insights into the basis of malignant transformation.
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