Supervisor: Dr. Sarah Teichmann

School: MRC Laboratory of Molecular Biology.

Highly Commended Talk

The basic nature of an organism is determined by its genes and by the regulatory network that governs the expression of these genes. Here we investigate the formation of regulatory networks that are currently known for the bacterium Escherichia coli and the eukaryote Saccharomyces cerevisiae. It is known that new proteins frequently evolve by gene duplication. Since the transcriptional interactions in gene regulatory networks consist of multiple components, the duplication processes generating new interactions are more complex. Here we define the possible duplication scenarios, and show to what extent they can be traced amongst the transcription factors and target genes in the E. coli and S. cerevisiae networks. Thus this work represents the first quantification of these processes across entire gene regulatory networks, and an analysis of how duplications relate to the topology of the networks. We show here that the duplications of genes, sometimes with regulatory regions, have contributed to network growth in over one third of the network in E. coli and almost one half in S. cerevisiae. In addition, we can conclude that duplication, a major driving force for regulatory network growth, is not primarily responsible for the overall network topology or specific topologies of network motifs. Instead, these features are the product of selection acting at a systems level.