Assigning Protein Function from Domain-Function Associations Using DomFun

Background: Protein function prediction remains a key challenge. Domain composition is key to understanding protein function, and domain-based prediction methods consistently perform well in challenges such as CAFA. Here we present DomFun, a Ruby gem that uses associations between protein domains and functions, calculated using multiple indices based on tripartite network analysis. These domain-function associations are combined at the protein level, to generate protein-function predictions. Results: We analysed 14 tripartite networks connecting homologous superfamily and FunFam domains from CATH-Gene3D with functional annotations from the Gene Ontology, KEGG, Reactome and the Human Phenotype Ontology. We validated the results using the CAFA 2 benchmark platform for GO and HPO annotation, finding Simpson's index combined with Stouffer's method led to the best performance in almost all scenarios. We also found that FunFams led to better performance than superfamilies, and better results were found for GO molecular function compared to GO biological process terms. Results were similar to other high-performing domain-based methods in CAFA 2. We also implemented our own benchmark procedure, Pathway Prediction Performance (PPP), which can be used to validate function prediction for additional annotations sources, such as KEGG and Reactome. Using PPP, we found similar results to those found with CAFA 2 for GO, moreover we found good performance for the other annotation sources. As with CAFA 2, Simpson's index with Stouffer's method led to the top performance in most scenarios. Conclusions: DomFun shows comparable performance to other methods evaluated in CAFA 2 when predicting human proteins function with GO. Through our own benchmark procedure, PPP we have shown it can also make accurate predictions for KEGG and Reactome. It performs best when using FunFams, combining Simpson's index derived domain-function associations combined using Stouffer's method. The tool has been implemented so that it could be easily adapted to incorporate other protein features, such as domain data from other sources. The DomFun Ruby gem is available from https://rubygems.org/gems/DomFun and its code is available at https://github.com/ElenaRojano/DomFun .