Regions essential for the interaction between Bcl-2 and SMN, the spinal muscular atrophy disease gene product

The SMN gene is implicated in spinal muscular atrophy (SMA), and its produc t has been shown to interact with Bcl-2 protein to enhance its anti-apoptot ic activity. In this study, we determined the regions that were essential f or the interaction of Bcl-2 and SMN by co-immunoprecipitation of deletion m utants. Bcl-2 lacking its amino-terminal 20 amino acid residues or its carb oxyl-terminal membrane-anchoring domain showed no or greatly reduced bindin g with SMN, respectively, However, Bcl-2 lacking other regions could still bind to SMN, Because Bcl-2 lacking the membrane-anchoring domain could bind to SMN in a yeast two-hybrid system, the amino-terminal region of Bcl-2 se ems to be the most important domain for binding with SMN, A fragment of SMN encoded by exon 6 could bind to Bcl-2, but SMN lacking this region could n ot. From these results, we concluded that Bcl-2 and SMN proteins bound with each other at the amino-terminal region near the BH4 domain of Bcl-2 and t he region encoded by exon 6 of SMN, both regions known to be important for their function.