Raf-1 interferes with Ras and Rap1A effector functions in yeast

R Ruggieri, SG Macdonald, M Callow and F McCormick

Onyx Pharmaceuticals, Richmond, California.

Raf-1 is a serine/threonine kinase that acts downstream of Ras in mitogenic signal transduction pathways, but the mechanism by which Ras transmits signals to Raf-1 is not known. We have examined the interaction between Raf-1 and human H-ras in three different systems that utilize H-ras-induced phenotypes in Saccharomyces cerevisiae. In each system, the effects of H-ras depend on guanosine triphosphate and appear to be mediated through the H-ras effector binding region. H-ras effector function was blocked in each case by expression of the N- terminal regulatory domain of Raf-1. These inhibitory effects did not require the Raf-1 kinase domain. Raf-1 also blocked Rap1A effector function in S. cerevisiae. Raf-1, therefore, appears to interact with H- Ras and Rap1A in these in vivo systems with properties that suggest it is an immediate downstream effector.

Volume 5, Issue 2, pp. 173-181, 02/01/1994
Copyright © 1994 by The American Society for Cell Biology

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