Expression of endogenous avian myeloblastosis virus information in different chicken cells

Abstract

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.

Density‐dependent arrest of DNA replication is accompanied by decreased levels of c‐myc mRNA in myogenic but not in differentiation‐defective myoblasts

“…Our results show that the three c-oncogenes c-myc, c-Ki-ras and c-abl are expressed in mouse and rat myoblasts, and that the expression of these genes is related to the state of differentiation and cell growth. In previous studies of muscle tissue from chicken, low levels of expression was found of c-myc, and also of c-erb (total), c-myb and c-yes, whereas no or extremely low amounts of transcripts were found of c-src, c-fps and c-ros (Gonda et al, 1982;Shibuya et al, 1982;Chen, 1980). In our studies of mouse and rat myoblast cultures, we have failed to detect transcripts of c-erbA, c-erbB, c-mos, c-fes and c-src (data not shown).…”

“…Although their precise role is unknown, it has been suggested that proto-oncogenes may be of key importance in the control of cell multiplication and differentiation. Studies of a variety of tissues from chicken and mouse have demonstrated that the expression of proto-oncogenes show various degrees of specificity for tissue (Chen, 1980;Gonda et al, 1982;Shibuya et al, 1982;Muller, 19831, stage of histotypic differentiation (Westin et al, 1983;Coll et al, 1983) and stage of embryogenesis (Chen, 1980;Muller, 1983;Muller et al, 1982;Slamon and Cline, 1984). It is, however, still not clear to what extent proto-oncogene expression is related to cell proliferation as such, to the commitment of cells for specific developmental pathways, and to expression of markers of histotypic differentiation.…”

RAV-1 insertional mutagenesis: disruption of the c-myb locus and development of avian B-cell lymphomas

“…Two examples of normal, early-stage, rapidly proliferating cells that express high levels of c-myb are thymocytes and embryonic yolk sac myeloblasts (12,41). A 25% decline in c-myb expression in total bursal RNA between day 18 of embryogenesis and the day of hatch has been reported (8). A study of murine pre-B-cell and B-cell lymphomas has correlated 10-fold higher c-myb expression with the pre-B-cell tumor and identified differences in transcriptional regulation that account for the expression levels (5,6).…”

Structure and transcription of the cellular homolog (c-myb) of the avian myeloblastosis virus transforming gene (v-myb)

“…Recent evidence suggests that the answer to the second question is positive (10,18); however, the answer to the first is not at all clear at the moment. Studies of the transcriptional expression of c-onc genes (7,13,30) have suggested that one of these genes, cmyb, the cellular homolog of the avian myeloblastosis virus (AMV) oncogene (v-myb), may have a role in hemopoiesis. The c-myb gene is also transcribed in several human hemopoietic tumor cells (29), although there is no evidence to suggest that c-myb expression in these cells has any role in their transformation.…”