Involvement of the abl oncogene in human chronic myelogenous leukemia.

The Philadelphia chromosome found in essentially all patients with chronic myelogenous leukemia is now known to express a chimeric mRNA of 8.5 kb derived from sequences on chromosome 22 and sequences on chromosome 9. The chromosome 9 component of the chimeric RNA is derived from a subset of the exons of the abl oncogene. A portion of the exonic sequences of a gene referred to as bcr on chromosome 22 make up the amino-terminal portion of this chimeric mRNA and gene product. Our laboratory has recently succeeded in obtaining full-length clones of the 8.5 kb mRNA. The sequence analysis of this large mRNA reveals an exceptionally G-C rich 5' untranslated region. A complete open reading frame initiating in sequences of the bcr gene and reading through the abl oncogene segment has been determined. The sequence also reveals an extremely high percentage of serine residues in the bcr segment of the chimeric protein.