Transcription enhancer identified near the human C_μ immunoglobulin heavy chain gene is unavailable to the translocated c-myc gene in a Burkitt lymphoma

Abstract

In Burkitt lymphoma the c-myc gene, the cellular homologue of the viral oncogene v-myc, has been implicated in the aetiology of this human B-cell malignancy. Burkitt lymphoma cells possess specific chromosomal rearrangements involving the region proximal to the c-myc gene and one of the three human immunoglobulin loci^1–9. The nature of the effect exerted by the immunoglobulin loci on the translocated c-myc gene is controversial: whereas some reports have suggested c-myc transcription is elevated in Burkitt lymphoma cells^10–12, others have suggested the level of transcription is unaffected by the translation⁹. Recently, transcription enhancer elements have been identified in the intron between the J_H and C_μ segments of the heavy-chain immunoglobulin gene in mice^13–15. If similar enhancers exist in humans they may lead to increased transcription of the translocated c- myc gene and thus contribute to oncogenesis in Burkitt lymphoma. We report here the identification of an enhancer element adjacent to the human C_μ gene on normal chromosome 14, but this enhancer does not remain on the abnormal chromosome 14 to which the c-myc gene has been translocated in the Burkitt lymphoma cell line Raji. This element is, therefore, not available for control of the translocated c-myc gene in this case.