title: Sequence of the murine and human cellular myc oncogenes and two modes of myc transcription resulting from chromosome translocation in B lymphoid tumours.
abstract: The 15;12 chromosome translocation in murine plasmacytomas and the 8;14 in human Burkitt lymphomas often link the cellular myc oncogene to the locus for constant regions of immunoglobulin heavy chains (CH locus). To clarify how and why c-myc translocation occurs, we have sequenced the mouse and human c-myc genes and correlated c-myc transcription with c-myc rearrangement. Both genes comprise three exons; the second and third encode the myc polypeptide, which is conserved between mammals and birds, particularly in its more basic C-terminal half. Southern blots showed that four of 12 Burkitt lines have c-myc linked near CH switch regions and two near the joining region (JH) locus. Hence, immunoglobulin recombination machinery may participate in translocation, although the common myc breakpoint region around exon 1 does not resemble a switch region. Tumours with breakpoints just 5' to exon 1, or distant from c-myc, had normal c-myc mRNAs of 2.25 and 2.4 kb, which differ at their 5' ends, while tumours with breakpoints within exon 1 or intron 1 had altered c-myc mRNAs (2.1-2.7 kb in Burkitt lines), initiated within intron 1. Both types of mRNAs probably yield the same polypeptide. Since the untranslocated c-myc allele was generally silent, translocation to the CH locus must induce constitutive c-myc expression. The presence of c-myc mRNA in immortal but non-tumorigenic lymphoblastoid cell lines may implicate c-myc in an immortalization step.
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002051:Burkitt Lymphoma / Q000235:genetics*; D002460:Cell Line; D004262:DNA Restriction Enzymes; D006801:Humans; D008223:Lymphoma / Q000276:immunology*; D051379:Mice; D009857:Oncogenes; D010954:Plasmacytoma / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics; D013045:Species Specificity; D014158:Transcription, Genetic; D014178:Translocation, Genetic
chemical_list: D012333:RNA, Messenger; D004262:DNA Restriction Enzymes