Genomewide trapping of genes that encode secreted and transmembrane proteins repressed by oncogenic signaling

A retroviral gene trap containing a human CD2 cell surface antigen/neomycin -phosphotransferase fusion gene in the U3 region of its LTR (U3Ceo) was use d to screen the mammalian genome for genes encoding secreted and/or transme mbrane proteins that are repressed by oncogenic transformation. From an int egration library consisting of Cells transformable by the insulin-like grow th factor 1 (IGF-1), a collection of neomycin resistant (Neo(R)) clones was obtained; 86% also expressed the CD2 cell surface antigen. Molecular analy sis of a random sample of Neo(R) clones revealed that the U3Ceo gene trap p referentially disrupted genes coding for secreted and transmembrane protein s. In each case, the signal sequence of the endogenous gene was fused in-fr ame to the CD2/neomycin-phosphotransferase reporter gene due to a cryptic s plice acceptor site embedded in the coding region of the CD2 cDNA. When the library was transformed by IGF-1 and selected against CD2 expression, inte grations were obtained in genes that are repressed by transformation. Molec ular analysis of six randomly chosen integrations revealed that, in each ca se, U3Ceo captured a Signal sequence from proteins involved in oncogenic tr ansformation and metastatic spread.