Premature transcript termination, trans-splicing and DNA repair: a vicious path to cancer.

So far, about 800 different chromosomal translocations have been characterized in hemato-malignant and solid tumors. Chromosomal translocations mostly result in the expression of chimeric fusion proteins associated with enhanced proliferation and/or malignant transformation. Here, we demonstrate that genes frequently involved in such genetic rearrangements exhibit a unique feature: premature transcriptional termination. These early-terminated RNA molecules have an abundance of 10-20% when compared to their cognate full-length transcripts. They exhibit an unsaturated splice donor site that gives rise to trans-splicing events, leading to RNAs displaying exon repetitions or chimeric fusion RNAs. These arbitrary fusion RNAs mimic the presence of a chromosomal translocation in genetically unaffected cells. Based on our and published data, we propose the hypothesis that these artificial "chimeric fusion transcripts" may influence DNA repair processes, resulting in the generation of de novo chromosomal translocations. This idea provides a rational explanation why different individuals suffer from nearly identical genetic rearrangements.