Hoenger Lab
University of Colorado at Boulder
Department of Molecular, Cellular and Developmental Biology

Biography for Sacha De Carlo

Since the beginning of his scientific career, Dr. De Carlo 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 he helped develop during his thesis work in Prof. Jacques Dubochet's lab in Lausanne (DeCarlo 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 Dr. De Carlo has focused during the past 4 years. Using single-particle 3D reconstruction techniques based on electron microscopy data, he and his colleagues 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, he and his colleagues were able to solve the structure of a very small human transcription factor, (hTFIIE, Jawhari et al. 2006) whose molecular weight (120kDa) 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. Recent work has focused on elucidating transcription initiation and regulatory mechanisms in Archaea (with K. Murakami, Penn State) and 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 of the NtrC family (NtrC, NtrC1, NtrC4). The group has made substantial progress in understanding the structural basis of the regulated assembly and function of NtrC and gained insight about it interaction with the sigma 54 factor.

Ph.D thesis "Cryo-negative staining: advantages & applications for three-dimensional electron microscopy of biological macromolecules", Université de Lausanne (2002). Available on http://www.planetesacha.com.