AN ALTERNATIVE TO PHOSPHOTYROSINE-CONTAINING MOTIFS FOR BINDING TO ANSH2 DOMAIN

She is an important signalling protein whose overexpression leads to c ell transformation in NIH 3T3 fibroblasts. Although the formation of S hc/Grb2 complexes involving She tyrosine residue 317 is necessary to i nduce this transformation, the She proteins in these Shc-overexpressin g cells are not substantially tyrosine-phosphorylated. This observatio n led to our hypothesis that the non-phosphorylated Tyr317-containing region of She might have specific affinity for the Grb2 protein. We sh ow here that cell-permeable peptides encompassing the She Tyr317 regio n, (FDD)-F-312-PSYVNVQNL(323), can bind to the SH2 domain of Grb2 rega rdless of the state of tyrosine phosphorylation. When delivered into c ells, both phosphorylated and non-phosphorylated She peptides inhibit growth factor-induced Shc/Grb2 protein-protein interaction, The non-ph osphorylated She peptides with single point mutations at Asp313, Asp31 4, or Tyr317 are inactive, suggesting that these residues play an impo rtant role in Grb2 protein recognition. Our findings represent the fir st paradigm of the specific interaction between an unphosphorylated ty rosine-containing region and an SH2 domain and have important implicat ions for understanding the mechanism of cell transformation by She ove rexpression. (C) 1997 Academic Press.