THE HUMAN DNA LOCUS RELATED TO THE ONCOGENE MYB OF AVIAN MYELOBLASTOSIS VIRUS MOLECULAR CLONING AND STRUCTURAL CHARACTERIZATION

Chicken and human cell DNA contains sequences homologous to the avian myeloblastosis virus oncogene, v-myb. These cellular sequences, c-myb (human) and c-myb (chicken), were isolated from libraries of human or chicken cell DNA fragments, generated by partial digestion with the restriction enzymes AluI and HaeIII and compared. The chicken c-myb locus isolated from 2 distinct overlapping recombinant phages, contained 5 contiguous EcoRI fragments of 5.4, 1.1, 2.1, 2.2 and 9 kbp [kilobase pair], accounting for all the bands seen with a v-myb probe in a complete EcoRI digest of chicken cellular DNA. Screening of the human library yielded a recombinant phage hybridizing with the v-myb specific probe, that contained 5 EcoRI fragments of 2.8, 2.6, 2.0, 1.2 and 5.0 kbp (the last ending with an artificial EcoRI site, due to the construction of the library) belonging to the c-myb (human) locus. Probes using the EcoRI chicken DNA cloned fragments revealed corresponding contiguous EcoRI fragments in the human clone. Subsequent analyses of cellular polyadenylated mRNA extracted from human and chicken cells allowed the identification of single RNA species of 3.8 and 4.0 kb, respectively, as the representative transcripts of the c-myb locus in the 2 spp. Thus, c-myb appears as a single locus in man and chicken, conserved with a similar structure in the 2 distantly related species. The preparation of a specific human c-myb probe with an increased sensitivity on DNA/RNA blots should facilitate analyses concerning this gene in human normal or tumor cells or tissues.