Example of network collapse into protein families. We show here part of the Literature Curated S. cerevisiae protein interaction network, involving interactions between certain components of RNA polymerases. A. The sub network in its original state. Nodes are colored according to their age (green: ABE, blue: AE/BE), individual families are in different shades of the same color. B. The subnetwork collapsed into protein families. C. Duplication in a single family: two edges that share a node (RBP5). D. Duplications in both families: non-overlapping edges (RPB2-RPO21, RPA135-RPA190, RET1-RPO31).