title: Comparative analysis of the Saccharomyces cerevisiae and Caenorhabditis elegans protein interaction networks.
abstract: BACKGROUND
  Protein interaction networks aim to summarize the complex interplay of proteins in an organism. Early studies suggested that the position of a protein in the network determines its evolutionary rate but there has been considerable disagreement as to what extent other factors, such as protein abundance, modify this reported dependence.
  
  
  RESULTS
  We compare the genomes of Saccharomyces cerevisiae and Caenorhabditis elegans with those of closely related species to elucidate the recent evolutionary history of their respective protein interaction networks. Interaction and expression data are studied in the light of a detailed phylogenetic analysis. The underlying network structure is incorporated explicitly into the statistical analysis. The increased phylogenetic resolution, paired with high-quality interaction data, allows us to resolve the way in which protein interaction network structure and abundance of proteins affect the evolutionary rate. We find that expression levels are better predictors of the evolutionary rate than a protein's connectivity. Detailed analysis of the two organisms also shows that the evolutionary rates of interacting proteins are not sufficiently similar to be mutually predictive.
  
  
  CONCLUSIONS
  It appears that meaningful inferences about the evolution of protein interaction networks require comparative analysis of reasonably closely related species. The signature of protein evolution is shaped by a protein's abundance in the organism and its function and the biological process it is involved in. Its position in the interaction networks and its connectivity may modulate this but they appear to have only minor influence on a protein's evolutionary rate.
authors.affiliation: Theoretical Genomics Group, Centre for Bioinformatics, Division of Molecular Biosciences, Imperial College London, Wolfson Building, London, SW7 2AZ, UK. ino.agrafioti@imperial.ac.uk
authors.forename: Ino
authors.initials: I
authors.lastname: Agrafioti
authors.forename: Jonathan
authors.initials: J
authors.lastname: Swire
authors.forename: James
authors.initials: J
authors.lastname: Abbott
authors.forename: Derek
authors.initials: D
authors.lastname: Huntley
authors.forename: Sarah
authors.initials: S
authors.lastname: Butcher
authors.forename: Michael P H
authors.initials: MP
authors.lastname: Stumpf
mesh_terms: D000818:Animals; D017173:Caenorhabditis elegans / Q000235:genetics*; D019143:Evolution, Molecular; D016678:Genome; D016013:Likelihood Functions; D015233:Models, Statistical; D010802:Phylogeny; D025941:Protein Interaction Mapping / Q000379:methods*; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D013045:Species Specificity