Multiple Roles of the SR Protein Family in Splicing Regulation

The serine and arginine-rich proteins (SR proteins) are a highly conserved family of essential pre-mRNA splicing factors. SR proteins have a modular domain structure consisting of RNA binding and protein-protein interaction modules. SR proteins function as molecular adapters, mediating interactions between the pre-mRNA and the assembling spliceosome. Unlike most essential splicing factors, SR proteins have acquired an inherent flexibility that allows them to function at numerous steps in spliceosome assembly and therefore, to play key roles in regulation of splice site selection. In the postgenomics era it is widely accepted that alternative splicing of pre-mRNAs may significantly expand the capacity of the genome to generate the functional complexity of the proteome. Therefore, it is essential to understand both the mechanisms of splice site selection and how trans-acting factors, such as the SR proteins, are regulated. Within this chapter we will discuss how the structure of SR proteins influences their roles in alternative splice site selection.