CHROMOSOME-TRANSLOCATION ACTIVATES HETEROGENEOUSLY INITIATED, BIPOLAR TRANSCRIPTION OF A MOUSE C-MYC GENE

In many mouse plasmacytomas, the active c-myc gene was truncated by chromosome translocation with the resultant severance of the protein-coding sequence from the normal promoter. Transcripts of such truncated c-myc genes were analyzed by Northern blotting, nuclease S1 mapping, primer extension assays and c [complementary] DNA cloning. Transcription originates from multiple initiation sites on both c-myc coding and non-coding strands with the 2-sets of transcripts derived from adjacent but essentially non-overlapping regions located > 1 kb [kilobase] from the translocation junction. In X63Ag8, where c-myc is translocated to the Ig C.gamma.2b gene, the c-myc non-coding strand transcripts include the translocation junction and then splice directly into the .gamma.2b CH1 exon. Chromosome translocation activates a cryptic promoter in the 1st intron and the heterogeneously initiated, bipolar transcription reflects the absence of a suitably placed TATA box element.