Biochemical and Biological Analyses of Farnesyl-Protein Transferase Inhibitors

Farnesyl-protein transferase (FPTase) catalyzes the postiranslational addition of the IScarbon isoprenoid, farnesyl, to approx 20 cellular proteins. Farnesylation is essential for the membrane localization and function of the modified proteins. Among these proteins are the products of the ras oncogenes, Harvey (Ha), Kirsten (Ki), and N-Ras. Ras is synthesized in the cytoplasm as a biologically inactive precursor that localizes to the plasma membrane and attains cell-transforming activity upon famesylation (1 –4 ). FPTase has therefore become a target for the development of inhibitors of Ras function, which will be effective against human tumors (5 –7 ), particularly leukemias and pancreatic and colon carcinomas where oncogenically mutated ras genes are frequently found (8 ). Here, we describe a series of in vitro, cell-based, and in vivo assays that permit the identification and characterization of inhibitors of FPTase.