Presence of a c-myc transcript initiated in intron 1 in Friend erythroleukemia cells and in other murine cell types with no evidence of c-myc gene rearrangement.

In Friend murine erythroleukemia cells, although no detectable c-myc gene rearrangement was found, we observed, in addition to the normal 2.3-kilobase c-myc transcript, the presence of a 2.3-kilobase c-myc mRNA initiated in intron 1 at a promoter site called P3. The intron 1-initiated transcript has a longer half-life than the normal c-myc mRNA. This c-myc transcript initiated in intron 1 was also found in other murine cell types where no rearrangement of the c-myc locus has been reported.