Thursday, February 2, 2012
Abstract: Genome-wide biological network has emerged as an important framework to decipher complex biological systems. In this talk we will discuss how the structure of certain biological networks reveals the design principles and evolutionary history of the corresponding biological regulatory systems. Many biological regulatory networks possess a preferred direction of information flow and thus exhibit a hierarchical organization. On the other hand, networks consist of over-represented motifs that are responsible for specific functions. We will examine these topological properties using various regulatory networks (transcriptional, phosphorylation) from simple organisms (E. coli, S. cerevisiae), together with multi-level regulatory networks constructed via systematic integration of the next-generation sequencing data and various high-throughput datasets in higher eukaryotes. To gain further intuition, we shall compare the above biological regulatory networks with commonplace networks such as the corporate hierarchy and the call graph of a computer operating system. Though a variety of design principles could be revealed based on network topology, in many cases one has to move a step forward to consider the underlying dynamical process. As a particular example, we shall address how fluctuations in protein abundance perturb the mass action equilibrium and propagate along the network in a genome-wide protein-binding network; in fact, network topology could be responsible for suppressing undesirable cross-talks.