Antibodies to the evolutionarily conserved amino-terminal region of the v-myb-encoded protein detect the c-myb protein in widely divergent metazoan species.

Abstract

Antibodies directed against a bacterial fusion protein that contains the domain encoded by the highly evolutionarily conserved 5' one-third of the v-myb oncogene of avian myeloblastosis virus (AMV) detect the protein products of various members of the myb gene family. Immunoprecipitation or immunoblot analyses with these antibodies yielded the following information. First, the products of the v-myb oncogenes of AMV (p48v-myb) and of E26 virus (p135gag-mybets) contain this highly conserved amino acid sequence, as previously hypothesized. Second, p75c mYb, the product of the chicken c-myb protooncogene, also contains this protein domain. Third, these antibodies have identified the products of the human, murine, and Drosophila c-myb genes, which were all found to be nuclear proteins of Mr 75,000-80,000. The human c-myb protein product is present in immature cells of the erythroid, myeloid, and lymphoid lineages.

A second c-myb protein is translated from an alternatively spliced mRNA expressed from normal and 5'-disrupted myb loci.

“…For our initial experiments, we used an antiserum raised against a bacterially expressed fragment of the N-terminal region of p45v-mYb (anti-Bp52-Myb-specific antibodies [5]) to identify Myb pro- ,. teins from extracts of 70Z mouse pre-B cells.…”

“…The anti-Myb serum was raised in a rabbit against a fusion protein encoding the 115 N-terminal amino acids of avian myeloblastosis virus p48v-m'b (the myb expression vector clone Bp52-Myb was kindly provided by J. Lipsick, University of California at San Diego) and has been previously characterized (5,19). …”

“…The c-myb proto-oncogene encodes a predominantly nuclear protein (c-Myb) with an apparent molecular weight of 75 to 80 kilodaltons in avian, murine, and human cells (5,15,16,18). Translation of murine c-Myb is thought to initiate at the first ATG in c-myb (located in exon UE3) and to terminate in a 3' exon downstream of vE7 (1, 10; Fig.…”

Identification of functional domains in the maize transcriptional activator C1: comparison of wild-type and dominant inhibitor proteins.

“…It is possible that this conservative amino acid change decreases CI DNA binding; however, the Cl-I protein (with Glu^°*) is believed to bind DNA (cited in Paz-Ares et al 1990). This Asp residue is conserved evolutionarily between the various members of the myb oncogene family (Bergmann et al 1981;Klempnauer et al 1982Klempnauer et al , 1986Gonda et al 1985;Boyle et al 1986;Shen-Ong et al 1986;Peter et al 1987) and may occupy a position in the DNA-recognition helix (Ohlendorf et al 1982;Lehming et al 1987;Aggarwal et al 1988;Jordan and Pabo 1988;Otting et al 1988). This conservation suggests that an analogous change in any of the various mammalian or insect myb-homologous domains could also decrease the transcriptional activation function of these proteins dramatically.…”

Hematopoietic lineage-specific heterogeneity in the 5'-terminal region of the chicken proto-myb transcript.

“…Chicken c-myb-related genes probably exist also but could be easily recognized by the extensive divergence of their nucleotide sequences. In metazoans, the c-myb gene encodes a nuclear phosphoprotein of Mr 75,000 to 80,000 that is associated primarily with the nuclear matrix, has a short half-life, binds to DNA, and seems to be a transcription regulator (6,22,26).…”