Description du projet
Structure du nucléosome et transcription de la chromatine
Le nucléosome constitue la partie fondamentale de la chromatine et aide à tasser l’ADN pour lui permettre de s’adapter au noyau de la cellule. La structure d’un nucléosome se compose de protéines histones entourées d’ADN. Les mécanismes moléculaires qui sous‑tendent la transcription de la chromatine restent mal compris, les études les plus importantes ayant été menées sur de l’ADN nu et non sur de la chromatine. Le projet CHROMATRANS, financé par l’UE, propose de franchir une nouvelle étape vers la compréhension du mécanisme de transcription et d’étudier la base structurelle de la transcription de la polymérase II (Pol II) de modèles de chromatine. Les principaux objectifs consistent à déterminer les structures des facteurs d’initiation liés aux nucléosomes, la structure du complexe de préinitiation Pol II sur le nucléosome au début de la transcription, ainsi que les structures des complexes d’élongation Pol II chez les mammifères.
Objectif
Transcription of protein-coding genes by RNA polymerase II (Pol II) governs cell identity and fate. We previously provided the structural basis of Pol II transcription initiation (ERC Advanced Grant TRANSIT: Sainsbury, Nature 2012; Lariviere, Nature 2012, Plaschka, Nature 2015) and of Pol II elongation regulation (ERC Advanced Grant TRANSREGULON: Vos, Nature 2018; Vos & Farnung, Nature 2018). These studies elucidated the mechanisms of transcription regulation. However, they were conducted on naked DNA, and not on chromatin, which is the natural template in cells and regulates transcription in many ways. As a consequence, the molecular mechanism underlying chromatin transcription and the regulatory interplay between chromatin and the transcription machinery remain poorly understood. Here I propose to take the next big step towards an understanding of the transcription mechanism and investigate the structural basis for Pol II transcription of chromatin templates. Integrated structural biology will provide structures of the transcription machinery on nucleosomal DNA. Nucleosomes are the building blocks of chromatin and regulate transcription in many ways. In particular, we will solve structures of pioneer factors bound to nucleosomes, to investigate how chromatin is opened locally for transcription (aim 1). We will solve the structure of the Pol II pre-initiation complex on the ‘+1’ nucleosome at the beginning of a gene, to understand how initiation is regulated by this specialized nucleosome (aim 2). Finally, we will determine structures of mammalian Pol II elongation complexes with many factors during nucleosome passage, to elucidate how Pol II transcribes chromatin (aim 3). Together with functional analysis in vitro and in vivo, these ground-breaking efforts will take the structural biology of transcription regulation to the chromatin level. The proposed research will also advance methods for the reconstitution and analysis of transient, higher-order complexes.
Champ scientifique
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Régime de financement
ERC-ADG - Advanced GrantInstitution d’accueil
80539 Munchen
Allemagne