Acquisition of viral DNA sequences in target organs of chickens infected with avian myeloblastosis virus

Genetic control of the organ specificity of lymphoproliferative disease virus (LPDV) of turkeys

In a previous study based on the kinetics of virus replication and tumor formation (Gazit et al., 1982), it was shown that the organotropism of lymphoproliferative disease virus (LPDV) is confined to lymphoid tissues. The present paper demonstrates that this organ specificity is controlled at the level of infection and integration, that is, the lymphoid organs, which are the only organs sustaining virus replication, and also the only organs in whose cells integrated LPDV proviruses are detectable. At the same time, the efficiency of virus replication within the various target organs is regulated both at the level of infection and integration and at the level of viral gene transcription.

Genetic regulation of CFA expression in interspecific avian hybrids and somatic cell hybrids

Chicken fetal-leukemic antigen (CFA) is an oncodevelopmental antigen present on embryonic and neonatal chicken peripheral red blood cells (RBCs) but is not restricted to fetal stages of development in other avian species. Crosses between white Leghorn chickens and Japanese quail resulted in adult hybrids whose peripheral RBCs were positive for CFA. Of the four CFA determinants normally found in adult quail RBCs, only two were present on quail-chicken hybrid RBCs. Adult quail--chicken hybrid RBCs also possessed on CFA determinant associated with early development in both quail and chicken and one chicken-specific CFA determinant. Evidence is presented for the possible association of CFA-positive adult peripheral RBCs and the level of circulating reticulocytes. Crosses between pheasant and turkey (both with CFA-positive adult RBCs) resulted in hybrid adult RBCs expressing only a portion of the parental CFA determinants. Through the formation of somatic cell hybrids between adult chicken and embryonic Japanese quail RBCs, it was possible to induce the appearance of CFA determinants normally restricted to embryonic chicken RBCs. Approximately 50% of the hybrid cells showed reexpression of CFA, and this induction was both time and temperature dependent. Hybridization between RBCs of adult chicken and those of either adult Japanese quail or adult turkey failed to elicit the reexpression of chicken-specific CFA.

Isolation of the mouse mammary tumor virus sequences not transmitted as germinal provirus in the C3H and RIII mouse strains

Radioactive 60-70S RNA from the mouse mammary tumor virus (MMTV) produced by the C3H mouse mammary tumor cell line (Mm5mt) hybridized to a greater extent, and at a lower Cot1/2 value, to the DNA of C3H mammary tumor cells than to the DNA of C3H liver cells. The 125I-labeled MMTV (C3H) 60-40S RNA was annealed to a vast excess of DNA from C3H livers, and single-stranded RNA was eluted from hydroxylapatite and recovered. This "recycled RNA" did not hybridize to the DNA of the apparently normal organs tested from normal or from mammary tumor-bearing C3H mice, but hybridized extensively to both the DNA from the C3H mammary tumor cell line and the DNA from spontaneous C3H mammary tumors. This hybridization could be competed out by the addition of unlabeled MMTV 60-70S RNA but was unaffected by the addition of unlabeled 60-70S RNA of C3H type C virus. Similar experiments were conducted with the RIII mouse strain. We therefore report on the isolation of the sequences of the RNA genomes of the MMTVs from C3H and RIII mice that are transmitted by some mechanism other than via the germ line. These studies further define the differences, via molecular hybridization, between the MMTV-S and the MMTV-L in both C3H and RIII mice.

Effect of Fv-1 gene product on proviral DNA formation and integration in cells infected with murine leukemia viruses

The amounts of unintegrated murine leukemia virus-specific DNA detected by molecular hybridization in extracts of Fv-ln/n (strains NIH/3T3, SIM) or Fv-lb/b (strains JLS-V9, SIM.R) mouse cells after infection with N- or B-tropic viruses were found to be the same in both permissive and resistant cells. Therefore, formation of DNA products from the viral RNA template does not appear to be grossly affected by the Fv-l gene product. Integration of virus-specific DNA into chromosomal cellular DNA was assayed by hybridization of radioactive complementary DNA to DNA from infected cells. With either NIH/3T3 or SIM.R cells infected with N- or B-tropic viruses, integration of proviral DNA could be detected in permissive cells but not in nonpermissive cells. The Fv-l gene product therefore appears to prevent integration of proviral DNA.

Evidence for tandem integration of avian myeloblastosis virus DNA with endogenous provirus in leukemic chicken cells

The integration site of avian myeloblastosis virus (AMV) proviral DNA in DNA from leukemia chicken myeloblasts has been studied by three sequential nucleic acid hybridizations that can localize the proviral DNA according to the repetitiveness of the adjacent cellular DNA regions. First, large denatured cellular DNA fragments (2.1 x 10(6) daltons) were reassociated and fractionated according to sequence reiteration frequenct. Next, DNA remaining single-stranded in each fraction was immobilized on nitrocellulose filters hybridized with an excess of unlabeled 70S RNA from Rous-associated virus-0 to saturate the endogenous proviral DNA sequences.

Germ line integration and Mendelian transmission of the exogenous Moloney leukemia virus

Mice were infected with the exogenous Moloney leukemia virus (M-MuLV) at two different stages of development. Either newborn mice (which can be considered as essentially fully differentiated animals) or preimplantation mouse embryos (at the 4-8 cell stage) were infected with M-MuLV. In both cases, animals that had developed an M-MuLV-induced leukemia were obtained. Two lines of evidence indicate that infection of preimplantation embryos, in contrast to infection of newborns, can lead to integration of the virus into the germ line. 1. Viremic males of the first backcross generation (N-1 generation) transmitted the virus to 50% of their offspring (N-2 generation) when mated with uninfected females. Likewise, a 50% transmission was observed from viremic N-2 and N-3 males to the next generations. 2. Molecular hybridization experiments revealed that viremic N-1 and N-2 animals carried one copy of M-MuLV per diploid mouse genome equivalent in all "non-target" organs tested. Together, both experiments indicate that the exogenous M-MuLV can be converted to an endogenous virus after infection of preimplantation embryos. The available evidence suggests that M-MuLV integrated into the germ line at one out of two possible integration sites. Thus, viremic backcross animals are heterozygous for a single Mendelian locus carrying the M-MuLV gene. During leukemogenesis an amplification of the M-MuLV from one copy to a maximum of four copies per diploid mouse genome equivalent takes place in the tumor tissues.