Mechanisms of pre-mRNA splicing: classical versus non-classical pathways

Abstract

Expression of genetic information proceeds through two major biological events, transcription and translation. However, in eukaryotic cells, the primary transcript (pre-mRNA) is not the template that the translational apparatus scans through, in order to produce the corresponding protein. Pre-mRNAs undergo several modifications (cap site addition, poly At tail addition) prior to becoming mature mRNAs, with the most important one being the excision (splicing) of the intronic sequences. Yet, the mechanisms that regulate the splicing process and the generation of alternatively spliced mRNA products are still poorly understood. Moreover recent findings suggest that this process also has the capability to produce an additional set of RNA products that differ from typical mRNA molecules. In these novel RNA transcripts the order of the exons has been changed relative to genomic DNA. Furthermore, the properties of these transcripts suggest that they may represent circular RNA molecules.