Caenorhabditis elegans [ABC.sub.RNAi] transporters interact genetically with rde-2 and mut-7

RNA interference (RNM) mechanisms are conserved and consist of an interrelated network of activities that not only respond to exogenous dsRNA, but also perform endogenous functions required in the fine tuning of gene expression and in maintaining genome integrity. Not surprisingly, RNAi functions have widespread influences on cellular function and organismal development. Previously, we observed a reduced capacity to mount an RNAi response in nine Caenorhabditis elegans mutants that are defective in ABC transporter genes (ABCRNAi mutants). Here, we report an exhaustive study of mutants, collectively defective in 49 different ABC transporter genes, that allowed for the categorization of one additional transporter into the [ABC.sub.RNAi] gene class. Genetic complementation tests reveal functions for [ABC.sub.RNAi] transporters in the mut7/rde-2 branch of the RNAi pathway. These second-site noncomplementation interactions suggest that [ABC.sub.RNAi] proteins and MUT-7/RDE-2 function together in parallel pathways and/or as multiprotein complexes. Like rrtut-7and rde-2, some ABCRNAi mutants display transposon silencing defects. Finally, our analyses reveal a genetic interaction network of [ABC.sub.RNAi] gene function with respect to this part of the RNAi pathway. From out results, we speculate that the coordinated activities of [ABC.sub.RNAi] transporters, through their effects on endogenous RNAi-related mechanisms, ultimately affect chromosome function and integrity.