Nucleotide sequence of cloned cDNA of human c-myc oncogene

Like other transforming genes of retro viruses, the v-myc gene of the avian virus, MC29, has a homologue in the genome of normal eukaryotic cells. The human cellular homologue, c-myc, located on human chromosome 8, region q24→qter (refs 1, 2), is translocated into the immunoglobulin heavy-chain locus on human chromosome 14 (ref. 3) in Burkitt's lymphoma^1,4,5, suggesting that c-myc has a primary role in transformation of some human haematopoietic cells. In addition, c-myc is amplified in the human promyelocytic leukaemia cell line, HL60 (refs 6, 7) which also contains high levels of c-myc mRNA⁸. Recently, Colby et al.⁹ reported the nucleotide sequence of the human c-myc DNA isolated from a genomic recombinant DNA library derived from human fetal liver¹⁰. This 4,053-base pair (bp) sequence includes two exons and one intron of the myc gene, and the authors have suggested the existence of a human c-myc mRNA of 2,291 nucleotides that has a coding capacity for a protein of molecular weight (M_r) 48,812. We have approached the problem of accurately defining the characteristics of the human c-myc mRNA and c-myc protein by determining the sequence of the c-myc cDNA isolated from a cDNA library prepared from mRNA of a clone of the K562 human leukaemic cell line¹¹. K562 cells are known to contain c-myc mRNA which is similar in size to the c-myc mRNA of other human cell types ⁸. We report here the sequence of 2,121 nucleotides of a human c-myc mRNA and demonstrate that its 5′ noncoding sequence does not correspond to the sequence of the reported genomic human sequence. However, our data confirm that the intact human c-myc mRNA can encode a 48,812-M_r protein with a sequence identical to that reported by Colby et al.⁹.