The French National Research Agency Projects for science

Voir cette page en français

ANR funded project

Blanc - SVSE 5 - Physique, chimie du vivant et innovations biotechnologiques (Blanc SVSE 5)
Edition 2011


Interactions between chromatin and the transcriptional co-activators TFIID, ATAC and SAGA

visualize gene expression to understand the various levels of its regulation
This project aims at studying the fundamental mechanisms that drive eukaryotic gene expression at the level of transcription initiation . Our bjective is to understand how protein nanomachines contribute to gene expression and its regulation

architecture of molecular assemblies that control gene expression
the level of gene expression, also called transcription, controls normal cell life but also its dysfunctions that promote cancer development or some rare genetic diseases. If the transcription of a particular gene could be controlled the cell fate would be mastered. This project aims at generating new knowledge on the fundamental mecanisms that drive gene expression. In the cell nucleus transcription is performed by molecular machines called RNA polymerases that copy faithfully the genetic information encoded by DNA. Other protein molecules, the transcription factors, select the usefull piece of information at each stage of the cell live and position precisely the RNA polymerase at the beginning of the gene of interest. The challenge of our research is to describe the architecture of these molecular complexes in order to understand how they act, and in the long term to be able to modify their action. Other factors affect gene expression, notably the way DNA is packaged into chromatin in the cell nucleus. Our observations aim at understanding the mechanism by which the packaging of DNA is modified to favor or to prevent transcription.

See protein nanomachines to understand their function
We aim at describing the shape and the movements of molecular assemblies controlling gene expresssion. We use an electron microscope to visualize these assemblies and image analysis methods to determine their three-dimensional shape. To prevent the dehydration of the molecules, they are frozen before being introduced into the vacuum of the microscope.


To be described


To be described

Scientific outputs and patents

To be described





ANR grant: 525 824 euros
Beginning and duration: janvier 2012 - 36 mois

Submission abstract

This research project aims at understanding the fundamental mechanisms of eukaryotic gene expression at the initiation step of gene transcription. The efforts of molecular biologists, structural biologists and biological chemists will be joined to explore this question in a multidisciplinary approach. Transcription of protein coding genes is regulated by coactivators; large macromolecular complexes whose action results in the assembly on the gene promoter of a preinitiation complex that contains the catalytic RNA polymerase II molecule and the general transcription factors. To activate gene expression, small activator proteins bind upstream of gene promoters to specific DNA sequences where they recruit the transcriptional coactivators. Interestingly activator binding sites may be located a few hundreds of base pairs upstream of the transcription start site or within enhancer sequences placed several thousands of base pairs away. How these long distance effects are mediated is presently poorly understood. Coactivators not only bridge activators with the preinitiation complex but also modify the chromatin organization of the gene promoters in order to give access to the transcriptional machinery and in addition read specific histone post translational modifications. Little is known on the structural organization of such large chromatin assemblies and on the complex network of interactions between activators, coactivators, chromatin and general transcription factors. Moreover evidence accumulates showing that coactivators collaborate to turn on a gene, suggesting that they play complementary roles. The exact cellular role of coactivators is poorly understood as they could participate in the long distance physical organization of the genome within the cell such as enhancer-promoter interactions or interactions between the 5’ and 3’ ends of a gene resulting in looping out of the gene body.
To answer these questions, the TFIID, SAGA and ATAC coactivators will be studied; each having specific activator, enhancer and promoter recognition characteristics. We plan to use a multi-resolution approach to analyze the molecular architecture of activated transcription initiation complexes that are formed in vitro or in vivo on nucleosome-containing DNA templates. We will combine state-of-the-art macromolecular purification methods, different high resolution electron microscopy and light microscopy imaging modalities, advanced image analysis protocols, high throughput Chromatin ImmunoPrecipitation methods as well as new antibody conjugation and delivery methods to address this biological question by an integrated structural biology approach. High resolution cryo-electron microscopy associated with single particle image analysis protocols will be used to determine structural models of the purified coactivator complexes. These models will be used as references to identify and position the coactivators in larger assemblies that will be either assembled in vitro from purified reagents or formed in vivo. The combination of Chromatin ImmunoPrecipitation and electron microscopy imaging will provide new insights in the role and promoter recognition specificity for each type of coactivator and shed new light on the local chromatin environment of coactivator-bound gene promoters as well as on long range interactions. Finally we aim at delivering antibodies coupled to electron dense particles into living cells in order to label and identify the co-activators in their cellular environment. The challenge of this part of the project is to detect specifically the coactivator complexes which are present in low copy numbers in each cell. The combined use of electron tomography and pre-embedding immunolabelling will constitute a breakthrough for many biological applications since it will permit the detection of nuclear proteins in their 3-D cellular environment at 3-4 nm resolution.


ANR Programme: Blanc - SVSE 5 - Physique, chimie du vivant et innovations biotechnologiques (Blanc SVSE 5) 2011

Project ID: ANR-11-BSV5-0010

Project coordinator:


Back to the previous page


The project coordinator is the author of this abstract and is therefore responsible for the content of the summary. The ANR disclaims all responsibility in connection with its content.