EXPLORING PROTEIN-PROTEIN INTERACTION NETWORKS IN LIVING CELLS : APPLICATION TO THE UBIQUITIN SYSTEM

Orateur : Gwenaël RABUT (Institute of Genetics & Development, Rennes)

Protein-protein interactions are essential to virtually all cellular processes. In this presentation, I will show how we are investigating the protein interaction network of ubiquitylation enzymes using budding yeast as a model organism. Ubiquitylation is a versatile post-translational protein modification. It is achieved through the concerted action of ubiquitin conjugating and ligating enzymes (E2s and E3s) that transiently interact with each other as well as with their modification substrates. These enzymes constitute a dynamic network that comprises more than 30 E2s and 600 E3s in human cells. Although the molecular determinants of E2-E3 interactions have been investigated for a few prototypical E2-E3 pairs, it is currently not possible to predict which E2s and E3s function together. Moreover, E2-E3 interactions are transient and therefore difficult to capture with classical biochemical approaches. To uncover new physiological E2-E3 pairs, we applied protein fragment complementation assays. I will present how these assays have enabled us to map the E2-E3 network in living cells and discuss their advantages and limitations as well as how they could be used to systematically explore protein-protein interaction networks.

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