SUBTRACTION CLONING OF H-REV107, A GENE SPECIFICALLY EXPRESSED IN H-RAS RESISTANT FIBROBLASTS

We have isolated by subtractive hybridization a novel gene, called H-r ev107, which is specifically expressed in a phenotypic revertant of H- ras transformed 208F rat fibroblasts. Apart from oncogene revertants, strong expression of H-rev107 was found in REF52 and EK-3 cells, two f ibroblast lines resistant to transformation by activated H-vas oncogen es. In contrast, transformation-sensitive fibroblasts like 208F or NIH 3T3 cells expressed only very little H-rev107 RNA. In H-r as or v-src transformed fibroblasts, H-rev107 RNA was undetectable. Introduction o f the adenovirus E1A nuclear oncogene into ras-resistant REF52 cells a bolished their transformation resistance and repressed the H-rev107 ge ne. H-rev107 encodes a protein with a molecular weight of 18 kDa witho ut any structural similarity to known proteins. p18(H-rev107) exists i n two forms which can be distinguished by their electrophoretic mobili ty; one is localized predominantly in cell membranes, the other in the cytoplasm. In confluent contact-inhibited 208F cells, p18(H-rev107) a ccumulated in cell membranes, while growth arrest induced by serum sta rvation did not induce H-rev107. In REF52, cell density had no influen ce on the expression or localization of p18(H-rev107). Repression of t he H-rev107 gene may be closely associated with the loss of density-de pendent growth inhibition and with the expression of the neoplastic ph enotype.