Figure 2

Protein interaction data are biased toward ubiquitously expressed genes and interactions. A. The fractions of proteins from the indicated interaction datasets that belong to each of three expression classes based on adult tissues: ubiquitous, non-ubiquitous non-specific (NUNS), and specific. B. The fraction of interactions involving tissue specific proteins that interact with ubiquitous, NUNS, or other tissue specific proteins. The tissue specific interactions include those from the same tissue (matched) or another tissue (other). Gene sets included all genes with tissue expression data (All Genes), and all genes with protein interactions in DroID (All Genes in PPI). Interaction data sets included data from yeast two-hybrid array screens (YTH Array), yeast two-hybrid cDNA screens (YTH cDNA), interologs from yeast, C. elegans, or human (Interologs), and protein interactions from co-affinity purification studies (coAP).