Group leader: Ronald Melki
Protein misfolding and subsequent aggregation is at the origin of over 20 human degenerative diseases termed “conformational” diseases. These diseases are intimately associated with ageing, a growing issue that our societies need to deal with. These diseases have high societal costs and lead to an extensive loss of life expectancy and a dramatic reduction in the quality of life.
In the yeast S. cerevisiae, the proteins Ure2 and Sup35 are at the origin of a protein-based structural heredity and give rise to the dominant, invasive and transmissible phenotypic traits [URE3] and [PSI+]. These harmless proteins, beside having prion properties, possess domains, essential for their oligomerization and aggregation, that are rich in Asn and Gln residues. They are therefore excellent models for in vitro and in vivo studies of the aggregation of human proteins rich in Gln and Asn such as huntingtin, a protein involved in the neurodegenerative Huntington’s disease.
Our group aims to better understand the molecular events at the origin of the structural transition from the folded, native and soluble form of polypeptides involved in “conformational diseases” to a persistent misfolded form that assembles into high molecular weight oligomers and fibrils that may cause cell death or the transmission of phenotypic traits. To this aim, a variety of in vitro and in vivo approaches involving molecular dynamics simulations, biochemical, biophysical, molecular and cell biological techniques are used.
Molecular basis of the oligomerization and assembly into fibrils of the prions Ure2p and Sup35p
Structure of Asn- and Gln-rich polypeptides such as Ure2p in their fibrilar state.
Role of the primary structure and key amino acid residues of prion and Asn- and Gln-rich polypeptides in oligomerization and fibrillogenesis
Molecular chaperones and the assembly of prion and Asn- and Gln-rich polypeptides
Role of the cytosolic chaperonin CCT in cell proliferation
Methods and expertise:
Protein expression (in bacteria and yeast) and purification ; site directed mutagenesis and protein labeling ; thermodynamic and kinetic (including rapid, stopped-flow) methods of protein-protein interaction and self-assembly ; Spectroscopy (UV, visible, IR, circular dichroism) ; spectrofluorimetry and light scattering ; proteomic methods (limited proteolysis, cross-linking, mass spectrometry) ; mapping of surface interfaces involved in protein-protein interactions (H/D exchange and mass spectrometry) ; protein crystallography and structural analysis ; electron microscopy