Systematic Interactome Mapping and Genetic Perturbation Analysis of a C. elegans TGF-β Signaling Network

To initiate a system-level analysis of C. elegans DAF-7/TGF-β signaling, we combined interactome mapping with single and double genetic perturbations. Yeast two-hybrid (Y2H) screens starting with known DAF-7/TGF-β pathway components defined a network of 71 interactions among 59 proteins. Coaffinity purification (co-AP) assays in mammalian cells confirmed the overall quality of this network. Systematic perturbations of the network using RNAi, both in wild-type and daf-7/TGF-β pathway mutant animals, identified nine DAF-7/TGF-β signaling modifiers, seven of which are conserved in humans. We show that one of these has functional homology to human SNO/SKI oncoproteins and that mutations at the corresponding genetic locus daf-5 confer defects in DAF-7/TGF-β signaling. Our results reveal substantial molecular complexity in DAF-7/TGF-β signal transduction. Integrating interactome maps with systematic genetic perturbations may be useful for developing a systems biology approach to this and other signaling modules.