Genetic and molecular study of components of the Caenorhabditis elegans RNAi machinery and their interplay with the NMD pathway

The regulation of accurate mRNA expression is amongst the essential functions of any cell. Recent evidence suggests that two pathways involved in regulating gene expression and controlling mRNA integrity, RNA interference [RNAi] and Nonsense Mediated Decay [NMD], might share common elements. In order to better understand characteristics of the RNAi machinery and its potential connection to NMD, we have utilized a combination of genetic and molecular tools.;We have developed an in-vivo cytolocalization assay to study the interaction between proteic factors required for each of the pathways. We observed several known and novel interactions among components of the RNAi and NMD pathways and found that the NMD component SMG-5 complexes with several proteins essential for RNAi. By testing the RNAi proficiency of animals mutant for each of the core components of the NMD machinery, we have obtained data suggesting that these proteins can have positive and negative effects on RNAi. This suggests a complex and intricate interaction between NMD and RNAi. None of the known RNAi components are essential for NMD, and we found that none of the NMD components are essential for RNAi.;We have performed a detailed domain analysis of the dsRNA binding protein RDE-4 and identified segments that are required for function and protein-protein interaction with its bona-fide binding partner DCR-1 and with SMG-5. Based on this data we have proposed a model for the RDE-4 activity.