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Professor Eduard Kellenberger (1920-2004) introduced me to classical EM when I was working under his supervision at the University of Lausanne, Switzerland (1996). Since then, my research has focused on 3D electron microscopy and computer-assisted image processing to study the structure, function and dynamics of molecular assemblies involved in fundamental biological processes such as protein folding and transcription. Cryo-EM and more specifically cryo-negative staining, which I helped develop during my thesis work with Dr. Marc Adrian, in Professor Jacques Dubochet's lab in Lausanne (De Carlo et al., 2002), have fostered substantial progress in studies of large biological assemblies. This is especially true in the important topic of gene regulation, upon which I have focused during the past 7 years. Using single-particle 3-D reconstruction techniques based on electron microscopy data, my colleagues and I were able to describe large flexible domains in both yeast RNA polymerase I (De Carlo et al., 2003) and human RNA polymerase II (Kostek et al., 2006).

Using the newly developed cryo-negative staining technique, we were able to solve the structure of a very small human transcription factor, (hTFIIE, Jawhari et al., 2006) whose molecular weight (110kDa) is twice as small as what is still considered the detectable size-limit for cryo-EM of single molecular species. This work demonstrates for the first time that the structure of such relatively small molecules can be obtained by cryo-EM. Recently we also showed that cryo-negative staining allows high-resolution single particles analysis: indeed, GroEL could be reconstructed at 10Å resolution (De Carlo et al., 2008).
This is the only work I could publish with my friend Nicolas Boisset (1964-2008). Unfortunately the paper appeared after he passed away, but it's nevertheless dedicated to him for his mentorship on image processing as well as his kindness towards me (attested by this recommendation letter from him).

Transcription Pre-Initiation Complex from Archaea (EMDB-5025)

In my lab we're mainly interested in transcription regulation in Bacteria (with Tracy Nixon, Penn State). The latter efforts are devoted to understanding a family of molecular motors that are involved in bacterial transcription activation, the enhancer-binding proteins (EBP) of the NtrC family (NtrC, NtrC1). We have made substantial progress in understanding the structural basis of the regulated assembly and function of NtrC (EM DataBase entry 1218) and gained insight about the interaction of EBP with the sigma (σ54) factor. Recent efforts are focused on larger molecular assemblies including the bacterial RNA polymerase (see this poster). We also worked on elucidating transcription initiation/elongation and regulatory mechanisms in Archaea (with D. Taatjes, Univ. of Colorado). Our results directly map the position of the initiation ‘core’ complex (TBP/TFB transcription factors) onto the archaeal RNA polymerase. This was recently confirmed by the Cramer lab (Kostrewa et al., 2009), and the Kornberg Lab (Liu et al., 2010).

Since April 2011 I work for FEI Company Europe, and supporting the Netherlands Center of Electron Nanoscopy at the University of Leiden, NL.

Faculté de Biologie et de Médecine