Functional alignment of regulatory networks: A study of temperate phages

The relationship between the design and functionality of molecular networks is now a key issue in biology. Comparison of regulatory networks performing similar tasks can give insights into how network architecture is constrained by the functions it directs. We here discuss methods of network comparison based on network architecture and signaling logic. Introducing local and global signaling scores for the difference between two networks we quantify similarities between evolutionary closely and distantly related bacteriophages. Despite the large evolutionary separation between phage $\lambda$ and 186 their networks are found to be similar when difference is measured in terms of global signaling. We finally discuss how network alignment can be used to to pinpoint protein similarities viewed from the network perspective.