Structure, expression, and chromosomal location of the human c-fgr gene.

Abstract

The nucleotide sequence of seven exons of the human c-fgr gene, a cellular homolog of the oncogene of Gardner-Rasheed feline sarcoma virus, was determined. Twenty-six independent genomic clones were obtained from a human gene library with a DNA clone of Y73 avian sarcoma virus oncogene, v-yes, as a probe under relaxed hybridization conditions. Restriction mapping and partial sequence analyses revealed that two of these clones were derived from the c-fgr gene, distinct from the c-yes gene. Interestingly, the splicing points of the c-fgr gene were identical with those of the c-src gene throughout the seven exons, suggesting that the two proto-oncogenes were generated by gene duplication of an ancestral gene containing intervening sequences. On RNA blot hybridization the major transcript was found to be 2.6 kilobases long. Two additional transcripts of 3.5 and 4.7 kilobases were also detected. Furthermore, karyotype analysis of several human-mouse hybrid cells and Southern blot analyses of DNAs of the hybrids with a human c-fgr locus-specific probe showed that this gene is located on chromosome 1.It is widely accepted that an acutely oncogenic retrovirus contains a viral oncogene that is derived from a cellular counterpart and is responsible for the initiation and maintenance of cellular transformation. In animals, cellular oncogenes have been highly conserved throughout evolution, suggesting that they play important roles in normal cells. However, the normal functions of most cellular oncogenes are still unknown (2). More than 10 oncogenes were found to be structurally related to the most well-characterized oncogene, the src gene of Rous sarcoma virus, and so are called the "src family." Most members of this gene family have been found to encode products that are associated with tyrosine kinase activity, and it is generally assumed that kinase activity plays a key role in cell transformation (2).In the src family, the yes gene, identified as an oncogene of avian Y73 sarcoma virus (15) Chromosome mapping. To determine the chromosomal location of the human c-fgr gene, we needed a human c-fgr-specific probe. For this purpose, we used an

Structure and expression of c-fgr protooncogene mRNA in Epstein-Barr virus converted cell lines

“…Sequences from regions of overlap with previously published genomic sequences (Parker et al, 1985;Nishizawa et al, 1986) exhibited 100% homology (data not shown). The sequence of the 5' end of the c-fgr mRNA, derived from clones pFd97 and pFa4, is shown in Figure 3 contain downstream termination codons, and the reading frame indicated is in phase with previously predicted aminoacid sequence .…”

“…Restriction maps of the inserts of the three longest clones (pFal, pFcl l & pFd97), each from the RPMI 4265 cDNA library, are shown in Figure 2. Together, the three clones span 2,347bp and the restriction maps of their central regions are colinear with previously published partial restriction maps of the c-fgr transcript, predicted from the sequences of genomic clones (Parker et al, 1985;Nishizawa et al, 1986).…”

“…In addition, this initiation codon obeys the rules of Kozak (1987). Taking these sequence data with those of Nishizawa et al (1986), the c-fgr protein would contain 529 amino-acids and would have a predicted molecular weight of -58,000. As shown in Figure 4, the N-terminal 75 amino-acids of the predicted cfgr protein have low homology with the N-termini of the predicted human lyn, hck, fyn, c-src and c-yes proteins.…”

Cellular proteins homologous to the viral yes gene product.

“…This is primarily because v-fgr is linked to the actin sequence at its amino terminus in the feline sarcoma virus genome (25,26,28), whereas c-fgr is not fused with actin sequences and may share homology with the amino-terminal region of c-yes. A published sequence of the human c-fgr protein in this region (29) indicates an homology of 20 of 24 amino acids in the carboxyl end of the v-yes polypeptide expressed as cI-yes-lacIZ.…”

The carboxy-terminal sequence of p56lck can regulate p60c-src.

“…Other genes in this family (the src family) are c-yes, c-fgr, fyn, hck, tkl, and lyn (17,25,26,29,34,36,37,40,42,43; for a review, see J. A. Cooper, in B. Kemp and P. F. Alewood, ed., Peptides and Protein Phosphorylation, in press).…”