How do disordered proteins contribute to DNA repair?
Proteins are the linchpins of living organisms. These biological macromolecules composed of a chain of amino acids adopt a three-dimensional arrangement, their structure, which allows them to perform their biological function. The structure of each protein is determined above all by the sequence of amino acids that compose it and whose physicochemical properties guide the folding of the protein chain on itself. While a large part of the regions of a protein are structured in folded domains, others are disordered and remain flexible in the native state. These disordered regions of proteins are "invisible" to the characterization methods classically used in structural biology such as X-ray crytallography or cryo-electron microscopy. To overcome this obstacle, the authors of this study used several techniques within the Infranalytics platforms in nuclear magnetic resonance (NMR) and electron paramagnetic resonance (EPR) to characterize these regions and in particular their role in the repair of broken DNA.
Chemists from the Physical Chemistry and Chemistry of Life laboratory (CNRS/ENS – PSL/Sorbonne University), biologists from the Cancer Research Center of Marseille (CNRS/Aix Marseille University/INSERM/Institut Paoli-Calmettes) and their collaborators focused on a group of proteins responsible for repairing these DNA double-strand breaks by the so-called "NHEJ" pathway.* This major pathway is used by human cells to counteract the effect of ionizing radiation such as that used in cancer radiotherapy, or the effect of free oxygen radicals which are by-products of biochemical reactions taking place in the body and particularly in brain cells, or during rearrangements of genes coding for antigen receptors responsible for the adaptive immune response.
In this study, NMR allowed us to show that the disordered regions of three central proteins of the NHEJ pathway participate in a myriad of weak and transient interactions. Together, all these weak interactions form a robust but dynamic network that generates the formation of a compartment around the fragmented DNA, literally a bioreactor that locally concentrates the reagents and greatly accelerates the kinetics of repair.
The new knowledge revealed by this work, published in the journal Nature Structural and Molecular Biology,will allow us to better understand how the NHEJ pathway protects genome integrity, with long-term applications in cancer therapy, immunodeficiency, and neurodegeneration. Potential applications in genome editing technologies, for example to correct a defective gene responsible for a disease, are also to be considered.
*Non-homologous end-joining (NHEJ) is a DNA repair mechanism that repairs lesions that cause double-strand breaks.
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Multivalent interactions of the disordered regions of XLF and XRCC4 foster robust cellular NHEJ and drive the formation of ligation-boosting condensates in vitro
Duc-Duy Vu, Alessio Bonucci, Manon Brenière, Metztli Cisneros-Aguirre, Philippe Pelupessy, Ziqing Wang, Ludovic Carlier, Guillaume Bouvignies, Patricia Cortes, Aneel K Aggarwal, Martin Blackledge, Zoher Gueroui, Valérie Belle, Jeremy M Stark, Mauro Modesti & Fabien Ferrage
Nature Structural and Molecular Biology 2024, 31, 1732-1744. DOI: 10.1101/2023.07.12.548668
Contacts:
Fabien Ferrage, researcher at the Physical Chemistry and Chemistry of Life laboratory (CNRS/ENS – PSL/Sorbonne University), This e-mail address is protected against spambots. You need JavaScript enabled to view it.
Mauro Modesti, INSERM researcher at the Cancer Research Center of Marseille (CNRS/Aix Marseille University/INSERM/Paoli-Calmettes Institute), This e-mail address is protected against spambots. You need JavaScript enabled to view it.