c-myc gene expression in a leukemic T-cell line bearing a t(8;14) (q24;q11) translocation

We have examined the expression of the c-myc protooncogene in human T-cell leukemic KE-37R cells carrying a t(8;14) (q24;q11) translocation. The breakpoint on chromosome 8 is located at 2.2 kb downstream of c-myc exon 3 and the 3′ part of the TcR-α gene (14q11) has been juxtaposed to c-myc. Our results showed that the steady-state levels of c-myc RNA transcripts were increased and the P₁/P₂ ratio of c-myc promoter utilization did not change, indicating that preferential utilization of P₂ was maintained in the rearranged gene. High levels of electrophoretically normal p64 and 67 c-myc proteins were detected and both products kept their instability. In addition, transcription from promoter P₀ was not detectable. Our results suggest that the activation of the gene is likely to result from its juxtaposition to the enhancer element of the TcR-α gene located downstream of the Cα region which stimulates constitutive synthesis of normal c-myc transcripts from the rearranged allele.