Co‐amplification of c‐myc/pvt‐1 in immortalized mouse b‐lymphocytic cell lines results in a novel pvt‐1/aj‐l transcript

Abstract

In a series of mouse pvt‐I cDNA clones prepared from an immortalized B‐cell line that contains an amplified c‐myc/pvt‐I region, we have identified a unique cDNA, AJ‐I, which contains 57 bp of pvt‐I sequence (pvt‐la) spliced to a novel sequence of 2.1 kb. We report here that this 3′ segment (termed AJ‐IX) maps more than 60 kb telomeric to pvt‐la and is encoded by novel locus (AJ‐I) on mouse chromosome 15. The AJ‐IX probe detects a transcript that is expressed only in normal mouse brain and testis. Several mast‐cell tumors, Ly‐I⁺ B‐lymphocytic cell lines and a neuroblastoma also display abundant levels of AJ‐IX‐specific mRNA. However, splicing of pvt‐la to AJ‐IX found exclusively in Ly‐I⁺ B‐cell lines that contain amplified c‐myc/pvt‐I. We conclude that some feature in the generation of this amplicon facilitates the synthesis of a pvt‐I/AJ‐IX chimeric mRNA that may play a role in immortalization of these Ly‐I⁺ B‐cell lines.