Human gene (c-fes) related to the onc sequences of Snyder-Theilen feline sarcoma virus

The human c-fps/fes gene product expressed ectopically in rat fibroblasts is nontransforming and has restrained protein-tyrosine kinase activity

A 13-kilobase EcoRI genomic restriction fragment containing the human c-fps/fes proto-oncogene locus was expressed transiently in Cos-1 monkey cells and stably in Rat-2 fibroblasts. In both cases, human c-fps/fes directed synthesis of a 92-kilodalton protein-tyrosine kinase (p92c-fes) indistinguishable from a tyrosine kinase previously identified with anti-fps antiserum which is specifically expressed in human myeloid cells. Transfected Rat-2 cells containing approximately 50-fold more human p92c-fes than is found in human leukemic cells remained morphologically normal and failed to grow in soft agar. Synthesis of p92c-fes in this phenotypically normal line exceeded that of the P130gag-fps oncoprotein in a v-fps-transformed Rat-2 line. Despite this elevated expression, human p92c-fes induced no substantial increase in cellular phosphotyrosine and was not itself phosphorylated on tyrosine. In contrast, p92c-fes immunoprecipitated from these Rat-2 cells or expressed as an enzymatically active fragment in Escherichia coli from a c-fps/fes cDNA catalyzed tyrosine phosphorylation with an activity similar to that of v-fps/fes polypeptides. Thus, p92c-fes is not transforming when ectopically overexpressed in Rat-2 fibroblasts. This lack of transforming activity correlates with a restriction imposed on the kinase activity of the normal c-fps/fes product in vivo which is apparently lifted for v-fps/fes oncoproteins, suggesting that regulatory interactions within the host cell modify fps/fes protein function and normally restrain its oncogenic potential.

The human c-fps/fes gene product expressed ectopically in rat fibroblasts is nontransforming and has restrained protein-tyrosine kinase activity

A 13-kilobase EcoRI genomic restriction fragment containing the human c-fps/fes proto-oncogene locus was expressed transiently in Cos-1 monkey cells and stably in Rat-2 fibroblasts. In both cases, human c-fps/fes directed synthesis of a 92-kilodalton protein-tyrosine kinase (p92c-fes) indistinguishable from a tyrosine kinase previously identified with anti-fps antiserum which is specifically expressed in human myeloid cells. Transfected Rat-2 cells containing approximately 50-fold more human p92c-fes than is found in human leukemic cells remained morphologically normal and failed to grow in soft agar. Synthesis of p92c-fes in this phenotypically normal line exceeded that of the P130gag-fps oncoprotein in a v-fps-transformed Rat-2 line. Despite this elevated expression, human p92c-fes induced no substantial increase in cellular phosphotyrosine and was not itself phosphorylated on tyrosine. In contrast, p92c-fes immunoprecipitated from these Rat-2 cells or expressed as an enzymatically active fragment in Escherichia coli from a c-fps/fes cDNA catalyzed tyrosine phosphorylation with an activity similar to that of v-fps/fes polypeptides. Thus, p92c-fes is not transforming when ectopically overexpressed in Rat-2 fibroblasts. This lack of transforming activity correlates with a restriction imposed on the kinase activity of the normal c-fps/fes product in vivo which is apparently lifted for v-fps/fes oncoproteins, suggesting that regulatory interactions within the host cell modify fps/fes protein function and normally restrain its oncogenic potential.

Expression of cellular oncogenes in primary cells from human acute leukemias

The structure and the expression of 11 cellular oncogenes (protooncogenes) were analyzed in primary cells from 20 acute lymphocytic (ALL) and 31 acute myelogenous (AML) leukemia patients. Neoplastic cells, obtained prior to initiation of therapy, were purified and classified, on the basis of both surface antigen pattern and morphology, into pre-B, B, and T ALL and M1-M5 AML. RNA was extracted and analyzed for expression of cellular oncogenes coding for nuclear proteins (c-myc, c-myb, c-fos), the beta-chain of platelet-derived growth factor (c-sis), growth factor receptors or related proteins (c-src, c-abl, c-fes, c-erbB), or putative intermediate transducers of mitogenic signals (c-Ha-ras, c-Ki-ras, c-N-ras). Quantitative analysis of total RNA was carried out by dot blot hybridization to specific cDNA or genomic probes. Number and size of transcripts were evaluated by blot hybridization of electrophoretically fractionated poly(A)+ RNA. Expression of c-myc and c-myb was detected in all leukemic cells at variable levels and was characterized by well-defined patterns within ALL subtypes. Conversely, significant levels of c-fos transcripts were detected only in myelomonocytic (M4) and monocytic (M5) leukemias. Among the "src-family," c-fes was expressed more in AML than ALL, and c-abl was expressed at variable but not elevated levels in all leukemia types. c-Ha-ras was uniformly expressed at low levels, as in non-neoplastic cells. c-Ki-ras transcription was detected only in T ALL; N-ras expression was barely demonstrable. The structure of these protooncogenes was not grossly modified, as evaluated by Southern analysis, except for c-myc rearrangement in B ALL. These studies indicate that cellular oncogene expression in specific subtypes of leukemic cells may relate to either the proliferative activity (c-myc, c-myb) or the differentiation state (c-fos) of the cells, or possibly to expression of receptors for putative hemopoiesis-related growth factors (c-fes, c-abl). Our data provide a basis for in-depth analysis of protooncogene expression in normal and neoplastic hemopoiesis.

Chromosomal mapping of murine c-fes and c-src genes

The murine homologs of two viral oncogenes associated with tyrosine-specific kinase activity have been assigned to different loci in the mouse genome. The segregation of restriction site polymorphisms, as detected by probes that are specific for endogenous c-fes and c-src sequences, was followed in the DNA of recombinant inbred strains. The c-fes gene was mapped to the proximal portion of chromosome 7, very close to the Gpi-1 locus, whereas c-src was linked to the Psp locus on the distal half of chromosome 2.

Chromosomal mapping of murine c-fes and c-src genes

The murine homologs of two viral oncogenes associated with tyrosine-specific kinase activity have been assigned to different loci in the mouse genome. The segregation of restriction site polymorphisms, as detected by probes that are specific for endogenous c-fes and c-src sequences, was followed in the DNA of recombinant inbred strains. The c-fes gene was mapped to the proximal portion of chromosome 7, very close to the Gpi-1 locus, whereas c-src was linked to the Psp locus on the distal half of chromosome 2.

Transforming potential of a human protooncogene (c-fps/fes) locus

The protooncogene c-fps/fes is a single vertebrate locus homologous to both the fps transforming gene of Fujinami avian sarcoma virus and the fes transforming gene of two feline sarcoma virus isolates. The human c-fps/fes locus has been previously cloned and characterized. We report that a recombinant gene in which 3' human c-fps/fes sequences replace over 80% of the feline sarcoma virus fes sequences transforms NIH 3T3 mouse fibroblasts and encodes a protein kinase. Cells transformed by this recombinant possess increased phosphotyrosine levels. These observations demonstrate that a large carboxyl portion of a human c-fps/fes protein product can functionally complement a retroviral transforming protein.

Structural organization and expression of human DNA sequences related to the transforming gene of avian myeloblastosis virus

Bacteriophage libraries of human DNA were screened for sequences homologous to the transforming gene (v-myb) of avian myeloblastosis virus. The three overlapping clones isolated were shown to contain a total of 1.0 kilobase pair (kbp) of sequence related to v-myb distributed over 6.2 kbp. Restriction enzyme mapping and heteroduplex analysis revealed the presence of five myb-related domains interrupted by four stretches of non-homology. To study the extent of human DNA coding sequences that constitute the myb gene homologue, c-myb (human), probes spanning about 30 kbp were prepared from the clones and used to study transcription in a human hematopoietic cell line (MOLT-4). Each of the probes hybridized a 4.5-kilobase transcript, which suggests that either the c-myb (human) gene encompasses 30 kbp or it contains two or more transcription units that each give rise to a mRNA of 4.5 kilobases.