Molecular cloning of the feline c-fes proto-oncogene and construction of a chimeric transforming gene

Structure of the feline c-fes/fps proto-oncogene: genesis of a retroviral oncogene

The nucleotide sequence of the feline c-fes/fps proto-oncogene was analyzed. Comparison with v-fes and v-fps revealed that all v-fes/fps homologous sequences were dispersed over 11 kilobase pairs in 19 interspersed segments. All segments, numbered exon 1 to exon 19 as in the chicken and human loci, were flanked by consensus splice junctions. The putative promoter region contained a CATT sequence and three CCGCCC motifs which were also found in the human locus at similar positions. About 200 nucleotides downstream of a translational stop codon in exon 19, a putative poly(A) addition signal was identified. Using the putative translation initiation codon in exon 2, a 93,000-molecular-weight protein could be deduced. This protein resembled very well the putative protein of the human c-fes/fps proto-oncogene (94% overall homology) and, although less well, the putative protein of the chicken c-fes/fps proto-oncogene (70% overall homology). As far as the feline c-fes/fps proto-oncogene sequences transduced to the Gardner-Arnstein (GA) and Snyder-Theilen (ST) strains of feline sarcoma virus (FeSV) are concerned, homology in deduced amino acid sequences between the GA- and ST-v-fes viral oncogenes and the proto-oncogene was 99%. Analysis of the recombination junctions between feline leukemia virus and v-fes sequences in GA- and ST-FeSV proviral DNA revealed for the left-hand junction the involvement of homologous recombination, presumably at the DNA level. The right-hand junction, which appeared identical in the GA-FeSV and ST-FeSV genomes, could have been the result of a site-specific recombination at the RNA level.

Characterization of human c-fes/fps reveals a new transcription unit (fur) in the immediately upstream region of the proto-oncogene

Comparison of nucleotide sequence data of the 5' region of a fes/fps viral oncogene with those of the v-fes/fps homologous regions of man and cat revealed the position of the 3' portion of an as yet unidentified c-fes/fps exon. Comparative Southern blot and heteroduplex analysis of human and feline DNA immediately upstream of the v-fes/fps homologous regions showed extensive but discontinuous homology over a 9 kbp DNA stretch, which we have designated as fur. Northern blot analysis of mRNA from KG-1 myeloid cells with fes/fps- or fur-specific probes revealed a 3.0 kb fes/fps and a 4.5 kb fur transcript. Analysis of a number of tissues of an adult Wistar Lewis rat for the presence of fur transcripts revealed its differential expression pattern. An 0.95 kbp fes/fps-related and a 2.2 kbp fur-related cDNA recombinant clone were isolated from an oligo(dT)-primed KG-1 cDNA library. Comparative nucleotide sequence analysis of the fes/fps cDNA and its human genomic counterpart indicated that the cDNA contained genetic sequences that were identical to and colinear with exon 15-19 and, furthermore, that the poly(A) addition signal near the 3' end of exon 19 was functional. Similar analysis of the 2.2 kbp fur cDNA indicated that the poly(A) addition signal of the fur transcript was in close proximity of the newly discovered fes/fps exon. The region in between contained a CATT sequence but no 'TATA' box. The fur transcript was characterized by a long noncoding region at its 3' end.