Expression in a RabGAP yeast mutant of two human homologues, one of which is an oncogene

Abstract

The yeast proteins Msb3p and Msb4p are two Ypt/Rab-specific GTPase-activating proteins (GAPs) involved in cell growth polarization. Both proteins share with a wide variety of other proteins the highly conserved TBC domain forming the catalytically active RabGAP domain. In particular, Msb3p and Msb4p are similar to the human proteins oncTre210p (the 786-amino-acid product of the human Tre2 oncogene, implicated in Ewing's sarcoma) and RN-tre (a Rab5-GAP controlling endocytosis of the EGFR). To further understand the biochemical function of Tre2 oncogene, we expressed its cDNA and, as a control, the RN-tre cDNA, in an msb3 msb4 double mutant yeast strain. Complementation data show that RN-tre can, unlike Tre2, replace the function of the MSB3 and MSB4 genes. As two highly conserved amino acids, including the catalytic arginine, are mutated in the oncTre210p TBC domain, we restored these two amino acids and expressed the modified Tre2 cDNA in the yeast mutant.