Deregulation of c-myc by Translocation of the α-Locus of the T-Cell Receptor in T-Cell Leukemias

Two human T-cell leukemias carrying a t(8;14)(q24;q11) chromosome translocation were studied for rearrangements and expression of the c-myc oncogene. For one leukemia, rearrangement was detected in a region immediately distal (3$^{\prime}$) to the c-myc locus; no rearrangements of c-myc were observed in the second case (DeF). However, studies with hybrids between human and mouse leukemic T cells indicated that in the leukemic cells of DeF, the breakpoint in chromosome 14 occurred between genes for the variable (V$_{\alpha}$) and the constant (C$_{\alpha}$) regions for the α chain of the T-cell receptor. The C$_{\alpha}$ locus had translocated to a region more than 38 kilobases 3$^{\prime}$ to the involved c-myc oncogene. Since human c-myc transcripts were expressed only in hybrids carrying the 8q+ chromosome but not in hybrids containing the normal chromosome 8, it is concluded that the translocation of the C$_{\alpha}$ locus 3$^{\prime}$ to the c-myc oncogene can result in its transcriptional deregulation.