Sam68Regulate The Alternative Splicing Of Survival Motor Neuron Gene (SMN)

Alternative splicing (AS) is a biological process which produces splicing isoforms bydifferent splicing ways. As a gene outputting mechanism, alternative splicing has beenfound in over95%of human genes, which increases the protein diversity. It has beenproved that many diseases involves with alternative splicing of pre-mRNA. Alternativesplicing mini system (AS-mini-system) is a new type of research technique in which asmall part of one gene is selected to depict its function, elucidate the regulatoryrelationship between the genes and splicing factors, and uncover the pathogenesis of somediseases. SMA is a common autosomal recessive hereditary disease which caused by thedegeneration of the spinal cord anterior horn motor neuron. The occurrence of this diseasecan be attributed to the homolog deleted of SMN1exons7and8, or exon7. A splicingvariant SMN2is produced by base displacement of SMN1exon7(+6Câ†'T). Molecularmechanism analysis of the SMA pathogenic mechanism certified that through control ofthe SMN splicing variants can promotes the retention of SMN2exon7, increase the SMNfull length protein (comes from SMN2),at last reduce the SMA clinical symptoms. Thesplicing of precursor mRNA was regulated by cis-elements, trans-factors and epigeneticfactors. Sam68is one of the newly discovered RNA metabolism regulatory proteins. Itparticipated in a variety of biological processes such as: signal transduction, cell cycleregulation, tumor suppressor, RNA metabolism, and so on. Besides, Sam68has a highaffinity with the regions in which riched in A or U, such as UAAA and UUUA. Sequenceanalysis of the SMN (exon7) proved that base displacement of SMN2exon7(+6Câ†'T)produced a potential regulatory site for Sam68in upstream of the binding site of hnRNP-A1. In order to test how Sam68to regulate the alternative splicing of SMN2and whether itcan remit the severity order of SMA through increasing the expression quantity of the fulllength protein SMN, both recombinant vectors, pcDNA3.1-SMN and pEGFP-C1-Sam68were constructed. Then, all of them were co-transfected into293T cells, which producedthe AS-mini-system. This system provides an efficient theoretical foundation for the SMA therapy in the alternative splicing level of the SMN pre-mRNA.