CHIMERIC TRANSCRIPTS WITH AN OPEN READING FRAME ARE GENERATED AS A RESULT OF TRANSLOCATION TO THE PVT-1 REGION IN MOUSE B-CELL TUMORS

Some mouse plasmacytomas exhibit a t(6; 15) chromosomal translocation in which the breakpoint resides within the Pvt-l locus located 260 kilobases (kb) downstream of c-myc on mouse chromosome 15. In this report, we show that the Pvt-l locus does not exhibit allelic exclusion in that Pvt-l transcripts continue to be expressed from the non-translocated allele in t(6;15) plasmacytomas. From the translocated allele, we find chimeric transcripts containing a short 57-bp segment of Pvt-l (termed Pvt-la) spliced directly to the immunoglobulin constant region sequence (Ig-Ck). These short transcripts have replaced a Jk segment with a trytophan residue via RNA splicing and contain a continuous open reading frame (ORF) from Pvt-la through tk. Since this Pvt-la/Ck transcript is found in all 3 t(6;15) plasmacytomas examined, regardless of the location of the chromosomal breakpoint, we suggest that the Pvt-la/Ck chimera may have a functional role in the development of mouse plasmacytomas. (C) 1994 Wiley-Liss, Inc.*