REV contains multiple sequence classes, some related to uninfected avian cellular DNA, but lacks detectable relatedness to mammalian DNAs despite reported protein similarities.
Reticuloendotheliosis virus (REV) is known to be capable of transforming chicken bone marrow cells in vivo and embryo fibroblasts in vitro. As with spleen necrosis virus, we have found that sequences related to REV are found in DNA of several uninfected avian species. For example, about 15% of the 3HcDNA synthesized in the endogenous reverse transcriptase reaction reassociated with DNA of uninfected chickens. Kinetic analysis revealed only a few (less than five) such sequences per haploid genome, and the thermal stability of the reassociated duplex indicated less than perfect complementarity. Comparison of REV propagated in an avian cell line with REV grown in a canine line has revealed clear differences between the two isolates. Viral RNA and 3HcDNA of REV isolated from the transformed chicken bone marrow cell line appear to consist of at least three sequence classes. The most numerous of these classes is highly related to REV propagated in canine cells. Only slightly less abundant is a class unrelated to RNA isolated from the canine virus but highly related to sequences found in normal uninfected avian cellular DNA. A third component is present at about 1% the level of the most numerous class. Although REV appears to be unrelated to the other known avian retroviruses, distant relatedness between p30's of REV and various mammalian type C viruses has recently been reported. We have asked whether REV-related sequences can be detected in various mammalian DNAs and viral RNAs. Hybridization experiments performed at low stringency have revealed no such sequences.
Simek et al. (Tue,) studied this question.