The exon 2b region of the spinal muscular atrophy protein, SMN, is involved in self-association and SIP1 binding

Spinal muscular atrophy (SMA) is caused by mutations in the SMN (survival o f motor neurons) gene and there is a correlation between disease severity a nd levels of functional SMN protein. Studies of structure-function relation ships in SMN protein may lead to a better understanding of SMA pathogenesis , Self-association of the spinal muscular atrophy protein, SMN, is importan t for its function in RNA splicing. Biomolecular interaction analysis core analysis now shows that SMN self-association occurs via SMN regions encoded by exons 2b and 6, that exon 2b encodes a binding site for SMN-interacting protein-1 and that interaction occurs between exon 2- and 4-encoded region s within the SMN monomer, The presence of two separate self-association sit es suggests a novel mechanism by which linear oligomers or closed rings mig ht be formed from SMN monomers.