Functions of sense-antisense chimeric transcripts in mRNA translation as a result of their structural characteristics

Chromosomal aberrations, especially the chimeric translocations, have been shown to play a role in the process of tumorigenesis. The joining of exons from two different genes due to the chromosome rearrangement or as a result of a complex splicing process leads to the production of chimeric RNAs. Numerous studies have been published on the functional role of various chimeras in cancer progression, neurological disorders and in other genetic abnormalities. Sense-antisense (SAS) chimeras were first reported in In ChiTaRS-2.1. These chimeric RNAs are produced by the coalescing of exons from two different strands of the same open reading frame and they produce fusion transcripts having both coding and non-coding exons of the same gene. These SAS chimeras are present in normal cells as well, but their appearance rate in cancer cells is significantly higher. We investigated the structural aspects of these SAS chimeras, particularly the role of the palindromic sequences that were present in the junction sites. We also assessed the behaviour of these genes in different cancers, to determine if they were oncogenes or tumour suppressors. From this study, on the basis of the results of gene enrichment, expression analysis and secondary structure evaluation, we hypothesize that these palindromic sequences are critical, as they may play a role similar to that of siRNA, interfering with the gene expression, degrading mRNA after transcription and thereby preventing further translation.