Avian myeloblastosis virus and E26 virus oncogene products are nuclear proteins.

Abstract

The defective acute leukemia viruses avian myeloblastosis virus (AMV) and E26 virus each contain an inserted cellular sequence related to the same highly conserved cellular gene, proto-amv. The oncogenes of these two retroviruses differ from this cellular proto-oncogene in gene structure, transcript structure, and gene product. AMV (7,8).In leukemic myeloblasts, the AMV oncogene is expressed as a 2-kb spliced subgenomic mRNA (9, 10). In contrast, proto-amv is expressed as a 4-kb transcript in normal and certain neoplastic hematopoietic tissues (11,12). This protoamv mRNA contains both 5' and 3' genetic information not present in AMV (ref. 13; unpublished data). In addition to differing gene and transcript structure, differing protein products of the AMV oncogene and proto-oncogene have also been found (3, 4).By using three antisera raised against different synthetic peptides predicted from the amv open reading frame, a common 48,000 Mr protein was specifically identified as the AMV oncogene product, p48mY', in AMV-transformed leukemic myeloblasts (3). The same three antisera also specifically precipitated a 110,000 Mr candidate normal cellular homolog, p110Protoa'v, in hematopoietic tissues that express the 4-kb proto-amv message (3).As a first approach to analyzing the functions of the AMV oncogene product, we have determined its-intracellular location. In addition, we have determined the location of the putative transforming protein, p135sag8""I'ts, of the E26 leukemia virus, which contains an oncogene with both amv-related and -unrelated cellular sequences (ets) (14-17). Leghorn chicken embryos (Pacesetter, Anaheim, CA). All cells except for the RP-9 cell line were cultured as described (3). RP-9 was maintained in liquid culture in the same media but supplemented with 20%o heat-inactivated chicken serum and 10% fetal calf serum. Avian erythroblastosis virus (AEV) was kindly provided by P. Duesberg (Molecular Biology Laboratory, University of California, Berkeley). MATERIALS AND METHODSCell Labeling. 4265The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely to indicate this fact.

Transformation by v-Myb

“…The proteins (Figure 1) The 48 kDa v-Myb protein encoded by AMV, the 135 kDa Gag-Myb-Ets protein encoded by the E26 virus, and the 75 kDa c-Myb protein are all nuclear and bind to the same DNA sequence (AACNG) (Biedenkapp et al, 1988;Boyle et al, 1983Boyle et al, , 1984Klempnauer et al, , 1984Klempnauer and Sippel, 1987). The sequence that de®nes the Myb family of proteins is an approximately 50 amino acid motif with a series of conserved residues including three tryptophans separated by a characteristic spacing (reviewed in Lipsick, 1996).…”

Myb binding sites within the N-ras promoter repress transcription

“…The 48 kD v-Myb protein is a truncated form of the 75 kD c-Myb protein which in addition to the N-and Cterminal deletions contains 11 amino acid substitutions. Both the c-Myb and the v-Myb proteins are localized in the nucleus (Klempnauer et al, 1984;Boyle et al, 1984), have short half-lives and bind to DNA in a sequence-speci®c fashion (Klempnauer and Sippel, 1987;Biedenkapp et al, 1988).…”

Transformation by v-myb correlates with trans-activation of gene expression.

“…In rare cases, certain individual sites (e.g., Avall at 960) were never mutagenized by this method, suggesting a strong restriction enzyme site preference during partial digestion in the presence of ethidium bromide. Target DNAs produced by enzymes which generated three-nucleotide 5 (21) and transfected by a modified calcium phosphate precipitation method (9). Two (17).…”