The Ig heavy chain 3' end confers a posttranscriptional processing advantage to Bcl-2-IgH fusion RNA in t(14;18) lymphoma

Abstract

The chromosomal translocation t(14;18) in lymphoma leads to an overproduction of the Bcl-2 protein on the basis of increased Bcl-2 mRNA levels. Whereas the juxtaposition of Bcl-2 with the Ig heavy chain locus causes a transcriptional activation, 70% of the lymphomas also produce Bcl- 2-Ig fusion RNAs with Ig 3' ends. Using S1 nuclease protection assays that can discriminate between nuclear RNA precursors and spliced mRNA, we found that the fusion RNAs in t(14;18) cell lines exhibit an additional posttranscriptional this effect is (1) related to RNA splicing and/or nucleocytoplasmic transport; (2) independent of transcriptional activation by the heavy chain enhancer; (3) dependent on the presence of the J(H)-C(H) and C-γ1 Ig introns; and (4) tissue specific for B cells. This constitutes a novel mechanism of oncogene deregulation unrelated to transcriptional activation or half-life prolongation. The data further support the existence of a tissue-specific posttranscriptional pathway of Ig regulation in B cells.