Alternative splicing of pvt-1 transcripts in murine lymphocytic-B neoplasms accompanies amplification and chromosomal translocation.

The Pvt-1 region lies approximately 260 kb 3' of the c-myc proto-oncogene on mouse chromosome 15. Chromosomal translocation or viral integration into the region of Pvt-1 in B-cell or T-cell neoplasms appears to up-regulate c-myc expression by some unknown mechanism. Recent isolations of Pvt-1-encoding cDNAs from both mouse and human tissues indicate that transcripts of Pvt-1 can be found in multiple forms. To elucidate the nature of these transcripts in the mouse, we have analyzed cDNAs from AJ9, an immortalized Ly-1+ B-lymphocytic cell line in which myc/Pvt-1 have been co-amplified, and from ABPC20, a plasmacytoma that contains a t(6;15) translocation in the region of Pvt-1. Alternatively spliced transcripts of Pvt-1 are evident, but a stretch of 57 bp makes up the amino-terminus in each of these cDNAs. This region, designated Pvt-1a, is part of exon 1 and is also found within a 140 aa open reading frame (ORF), the longest Pvt-1 ORF established to date. Pvt-1a also shows homology at the amino acid level with two enzymes associated with transport in E. coli, glutamine permease operon protein glnQ and glycerophosphoryl diester phosphodiesterase glpQ. We predict that such chimeric mRNAs generated in mouse B-cell lymphomas and plasmacytomas with amplified or translocated Pvt-1 sequences may encode an in-frame segment of Pvt-1a.