Berger Group

Previous and current research

An intense focus of current biological research efforts is the elucidation of protein interaction networks (interactome). Many large multiprotein complexes are discovered. This poses considerable challenges for molecular level studies, in particular for eukaryotic multiprotein complexes with intracellular quantities refractory to large-scale extraction from source. Our research is focused on developing new technologies to obtain, within a reasonable time-frame, well-defined and homogeneous samples of human multiprotein assemblies in transcription and hereditary disease, which we then use for high-resolution structural and functional analyses.

Our major methodologies include molecular biology and X-ray crystallography. However, we readily apply techniques from other fields that are required for our research, both by ourselves and through collaborative efforts. A prerequisite for successful structural study of many complexes, both by electron microscopy and X-ray crystallography, is production of homogeneous, stable specimens. Present recombinant expression methods often require considerable investment in both labour and materials before multiprotein expression, and after expression and biochemical analysis do not provide flexibility for expressing an altered multiprotein complex. To meet these demands, we have developed our MultiBac system, a modular, baculovirus based technology specifically designed for eukaryotic multiprotein expression. MultiBac is now being used successfully in many laboratories worldwide, not only by structural biologists but also for applications as diverse as the development of vaccines and gene therapy vectors. In our lab, we have recently harnessed homologous and site-specific recombination methods in tandem for all steps involved in multigene assembly, and we have successfully implemented all steps involved in a robotics setup by developing ACEMBL, a proprietary automated suite for multigene recombineering on our TECAN EvoII platform. By using our technology, we produced numerous large multiprotein assemblies in sufficient quantity and quality for structural studies, including large multi component membrane protein complexes and a 1MDa core assembly of human TFIID general transcription factor.

Future projects and goals

At EMBL Grenoble, we continue to advance our expression technologies to entirely automate and standardise the process of production for eukaryotic gene regulatory multiprotein complexes including the entire human TFIID holoenzyme, its various isoforms and other components of the preinitiation complex. In collaboration with the Schaffitzel Group and the Schultz Group at IGBMC Strasbourg, we subject the complex specimens produced to electron microscopic analyses. We use homogenous complexes thus identified for X-ray crystallography. We strive to understand physiological function, and we explore and challenge our structural findings by in vitro and in vivo biochemical analysis.

By enlisting state-of-the-art mass spectrometric methods from systems biology, we are addressing a further bottleneck in complex crystallography, namely the challenge of defining crystallisable core assemblies of multiprotein complexes in a reasonable time frame (a collaboration with ETH Zürich and Lund University). Also, we are expanding our multiprotein expression strategies to prokaryotic and mammalian hosts.