Sm and Sm-like (Lsm) proteins are core components of ribonucleoprotein complexes essential to key nucleic acid processing events such as pre-mRNA splicing, mRNA degradation and histone processing. The proteins assemble as multi-unit ring scaffolds that bind RNA substrates and other necessary protein factors. Our recent crystal structure of the octameric yeast Lsm3 ring, alongside solution NMR studies, reveals a new organization for these proteins, as well as a mechanism for recruitment of other protein components to the RNP scaffold. In vivo, seven Lsm proteins form hetero-complexes, the exact components of which dictate their specific biological function. By engineering appropriate polyproteins, we have now begun to probe the structural and functional features of both mRNA-degrading Lsm[1-7] complex, as well as the U6 component Lsm[2-8].