Cloning and sequencing of the cDNA for the cph oncogene from neoplastic hamster fibroblasts reveal partial homology with the dbl exchange factor

Abstract

The combination of in vitro transformation protocols and transfection assays allowed us to isolate a new transforming gene, cph, from neoplastic Syrian hamster embryo fibroblasts chemically initiated with a single dose of 3-methylcholanthrene. Cosmid clones encompassing cph genomic sequences were able to transform NIH/3T3 cells and showed a synergistic action with H-ras in the transformation of the murine fibroblasts. In the present study, we describe the molecular cloning of the hamster cph oncogene cDNA. Nucleotide sequence analysis of a full-length cDNA clone (pBl-19), isolated from a cDNA library from neoplastic hamster cells with cph genomic probes demonstrated that the cloned cph cDNA does not show any significant global homology to sequences deposited in established databases, confirming that cph is a novel gene. The cph cDNA contained an open reading frame with coding capacity for a protein of about 26 kDa, which was synthesized from pBl-19 by using in vitro transcription-translation assays. The cph protein deduced from the cDNA nucleotide sequence contained a dbl-homologous (DH) domain. The fact that the DH domain has been found primarily among GDP-exchange factors suggests that cph may be a new member of this family of proteins. © 1996 Wiley-Liss, Inc.