Expression of endogenous avian myeloblastosis virus information in different chicken cells.

Uninfected chicken cells were found to contain endogenous avian myeloblastosis virus (AMV)-specific information. Different tissues from chicken embryos and chickens expressed different amounts of the AMV-specific information. The endogenous AMV-related RNA was most abundant in bone marrow cells, which contained about 20 copies per cell. About 5 to 10 copies of AMV endogenous RNA per cell were found in embryonic yolk sac cells and bursa cells. The spleen, muscle, liver, and kidney cells of chickens and the fibroblasts of chicken embryos contained about two copies per cell. The amounts of AMV endogenous RNA in bone marrow, yolk sac, and bursa varied with age. From 19-day-old embryos to 2-week-old chickens, the bone marrow contained 20 copies of AMV RNA per cell. Bone marrow cells from 2-year-old chickens contained five copies per cell. Yolk sac cells of 10-day-old embryos and 1-day-old chickens were found to contain two copies per cell, whereas in 15- to 17-day-old embryos, these cells contained 5 to 10 copies. These results indicate that the level of endogenous AMV expression correlates with the development of granulopoiesis of the chicken hemopoietic system. The results of experiments on the thermostability of RNA-DNA hybrids indicated that the endogenous AMV RNA is closely related to viral AMV RNA. The expression of endogenous AMV information is independent of the activity of the chick helper factor. This endogenous AMV information is expressed as 20 to 21S RNA in both bone marrow and yolk sac cells.