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Cell. 1991 Nov 15;67(4):701-16.

Ras1 and a putative guanine nucleotide exchange factor perform crucial steps in signaling by the sevenless protein tyrosine kinase.

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1
Howard Hughes Medical Institute, University of California, Berkeley 94720.

Abstract

We have conducted a genetic screen for mutations that decrease the effectiveness of signaling by a protein tyrosine kinase, the product of the Drosophila melanogaster sevenless gene. These mutations define seven genes whose wild-type products may be required for signaling by sevenless. Four of the seven genes also appear to be essential for signaling by a second protein tyrosine kinase, the product of the Ellipse gene. The putative products of two of these seven genes have been identified. One encodes a ras protein. The other locus encodes a protein that is homologous to the S. cerevisiae CDC25 protein, an activator of guanine nucleotide exchange by ras proteins. These results suggest that the stimulation of ras protein activity is a key element in the signaling by sevenless and Ellipse and that this stimulation may be achieved by activating the exchange of GTP for bound GDP by the ras protein.

PMID:
1934068
[Indexed for MEDLINE]

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