Characterization of the transformation-specific sequences of avian erythroblastosis virus in normal vertebrate cells

Dispersed chromosomal localization of the proto-oncogenes transduced into the genome of Mill Hill 2 or E26 leukemia virus

Both Mill Hill 2 and E26 retroviruses have transduced two cellular genes--c-myc and c-mil/mht (Mill Hill 2) and c-myb and c-ets (E26). We localized the genes transduced by these viruses to different chromosomes: c-myc and c-myb to relatively large chromosomes and c-mil/mht and c-ets to microchromosomes. Thus, like avian erythroblastosis virus, each of these retroviruses has transduced two cellular genes unlinked in the chicken genome.

Cellular oncogenes (c-erb-A and c-erb-B) located on different chicken chromosomes can be transduced into the same retroviral genome

Avian erythroblastosis virus has transduced two cellular genes, c-erb-A and c-erb-B. Using fractionated chicken chromosomes, we found that the two genes are located on different chromosomes in the chicken genome: c-erb-A is on a microchromosome, and c-erb-B is on a large chromosome. The locations of two other cellular oncogenes (c-fps and c-myb) were also determined: c-fps is on a microchromosome, and c-myb is on chromosome of an intermediate size. Our results suggest that avian erythroblastosis virus had transduced the two cellular genes independently, conforming to previous indications that cellular oncogenes are dispersed among multiple chromosomes in every species that has been examined.

Cellular oncogenes (c-erb-A and c-erb-B) located on different chicken chromosomes can be transduced into the same retroviral genome

Avian erythroblastosis virus has transduced two cellular genes, c-erb-A and c-erb-B. Using fractionated chicken chromosomes, we found that the two genes are located on different chromosomes in the chicken genome: c-erb-A is on a microchromosome, and c-erb-B is on a large chromosome. The locations of two other cellular oncogenes (c-fps and c-myb) were also determined: c-fps is on a microchromosome, and c-myb is on chromosome of an intermediate size. Our results suggest that avian erythroblastosis virus had transduced the two cellular genes independently, conforming to previous indications that cellular oncogenes are dispersed among multiple chromosomes in every species that has been examined.

Chromosomal clustering of five defined endogenous retrovirus loci in White Leghorn chickens

By using in situ hybridization, we localized three endogenous chicken retrovirus loci associated with the gs- chf- phenotype to distinct regions on chromosome 1. These three loci, ev4, ev5, and ev8, along with the two other known gs- chf--associated loci in White Leghorn chickens, ev1 and ev13, appear to be evenly distributed along chromosome 1, occurring approximately every 1.8 X 10(7) base pairs. The presence of all five loci on chromosome 1 represents a highly nonrandom distribution and all but eliminates a mechanism of independent random integration events for the generation of these loci.

Target cells infected by avian erythroblastosis virus differentiate and become transformed

Transformation in vitro of bone marrow cells by avian erythroblastosis virus (AEV) gives rise to rapidly growing cells of erythroid nature. Target cells of neoplastic transformation by AEV are recruited among the early progenitors of the erythroid lineage, the burst-forming units-erythroid (BFU-E). They express a brain-related antigen at a high level and an immature antigen at a low level. We show that AEV-transformed cells express low levels of the brain antigen and high levels of the immature antigen. Their response to specific factors regulating the erythroid differentiation indicates that they are very sensitive to erythropoietin. Furthermore, cells transformed by a temperature-sensitive mutant of AEV differentiate into hemoglobin-synthesizing cells 4 days after being shifted to the nonpermissive temperature. All these properties are similar to those of late progenitors of the erythroid lineage, the colony-forming units-erythroid (CFU-E). These results indicate that the AEV-transformed cells are blocked in their differentiation at the CFU-E stage.