Dr. Ruth Williams ( UCSD Math Dept)

Tittle: Queueing up for enzymatic processing: correlations through coupled degradation

Abstract: A major challenge for systems biology is to deduce the molecular interactions that underlie correlations observed between concentrations of different intracellular molecules. Although direct explanations such as coupled transcription or direct protein-protein interactions are often considered, potential indirect sources of coupling have received much less attention. Here we show how correlations can arise generically from a posttranslational coupling mechanism involving the processing of multiple protein species by a limited number of copies of a common enzyme. By observing a connection between a stochastic model and a multiclass queue, we obtain a closed form expression for the steady-state distribution of the numbers of molecules of each protein species. From analytic expressions for the moments and correlations associated with this distribution, we observe a striking phenomenon that we call correlation resonance: for small dilution rate, correlations peak near the balance-point where the total rate of influx of proteins into the system is equal to the maximum processing capacity of the enzymes. The talk will describe the theoretical developments and the results of related experiments. As time allows, a generalization to time-dependent distributions for enzymatic processing networks will be discussed.

Based on joint work with Natalie Cookson, Tal Danino, Jeff Hasty, Will Mather, Octavio Mondragon-Palomino, Lev Tsimring.