Abstract
Members of the Rho/Rac/Cdc42Hs family of GTPases have been shown to participate in many aspects of the signaling of cell growth and differentiation. Although the biochemical properties of these GTPases have been extensively studied, very little is known about their gene structure and regulation. RhoG, a member related to Rac and Cdc42Hs, is activated at the transcriptional level in the mid-G1 phase of stimulated fibroblasts. As a first step toward the characterization of the regulatory elements involved in serum-regulated expression, we isolated and determined the structure of the corresponding human locus (ARHG, localized in 11p15.4-p15.5). This is the first gene structure of a member of the Rho/Rac/Cdc42Hs family. At variance with Ras and Rab3A genes, ARHG contains a single intron larger than 20 kb that splits a 62-nt-long 5' noncoding first exon from the rest of the mRNA. The sequences upstream of the cap sites exhibit transcriptional activity. They are G/C-rich and devoid of TATA or CAAT boxes, as found for many housekeeping genes, including Ras genes.