p190-A, a human tumor suppressor gene, maps to the chromosomal region 19q13.3 that is reportedly deleted in some gliomas

To date, two distinct genes coding for Ras GAP-binding phosphoproteins of 190 kDa, p190-A and p190-B, have been cloned from mammalian cells. Rat p190-A of 1513 amino acids shares 50% sequence identity with human p190-B of 1499 amino acids. We have previously demonstrated, using rat p190-A cDNA, that full-length p190-A is a tumor suppressor, reversing v-Ha-Ras-induced malignancy of NIH 3T3 cells through both the N-terminal GTPase (residues 1–251) and the C-terminal Rho GAP (residues 1168–1441) domains. Here we report the cloning of the full-length human p190-A cDNA and its first exon covering more than 80% of this protein, as well as its chromosomal mapping. Human p190-A encodes a protein of 1514 amino acids, and shares overall 97% sequence identity with rat p190-A. Like the p190-B exon, the first exon of p190-A is extremely large (3.7 kb in length), encoding both the GTPase and middle domains (residues 1–1228), but not the remaining GAP domain, suggesting a high conservation of genomic structure between two p190 genes. Using a well characterized monochromosome somatic cell hybrid panel, fluorescent in situ hybridization (FISH) and other complementary approaches, we have mapped the p190-A gene between the markers D19S241E and STD (500 kb region) of human chromosome 19q13.3. Interestingly, this chromosomal region is known to be rearranged in a variety of human solid tumors including pancreatic carcinomas and gliomas. Moreover, at least 40% glioblastoma/astrocytoma cases with breakpoints in this region were previously reported to show loss of the chromosomal region encompassing p190-A, suggesting the possibility that loss or mutations of this gene might be in part responsible for the development of these tumors.