The Roquin protein, discovered in 2005, controls T-cell activation and differentiation by regulating the expression of certain mRNAs. In doing so, it helps to guarantee immunological tolerance and prevents immune responses against the body's own structures that can lead to autoimmune disease. Roquin is thus an immune regulator. Autoimmune diseases affect between five and ten per cent of the population. They usually occur as a result of complex environmental influences when a genetic predisposition exists. Only in rare cases the development of the disease is determined by a single mutated gene. However, a single mutation in the Roquin gene in a mouse model was shown to be responsible for the development of the autoimmune disease systemic lupus erythematosus. This mutation in the Roquin protein also led to a high susceptibility to type 1 diabetes and rheumatoid arthritis and induced angioimmunoblastic T-cell lymphoma.
Elucidation of the three-dimensional structure of the Roquin-RNA complex
An interdisciplinary team comprising the research groups led by Prof. Michael Sattler, Dr. Dierk Niessing and Prof. Vigo Heissmeyer at the Helmholtz Zentrum München, Ludwig-Maximilian University (LMU) and the Technische Universität München (TUM) has now revealed unprecedented insight into how Roquin recognizes its RNA binding partner and thereby controls T-cell functions. To this end, the scientists Dr. Andreas Schlundt, Gitta Heinz, and Dr. Robert Janowski used the X-ray crystallography platform of the Helmholtz Zentrum München to determine the spatial structure of the RNA binding domain of Roquin when bound to its RNA target. The interaction of Roquin with additional RNA binding partners was studied in solution using nuclear magnetic resonance (NMR) spectroscopy at the Bavarian NMR Center, a joint research infrastructure of the Helmholtz Zentrum München and TUM. Furthermore, the researchers could confirm the biological significance of the molecular recognition of the RNA by studying Roquin-dependent gene regulation in cellular systems.
The results obtained reveal for the first time the molecular interactions with which roquin recognizes a binding motif in a gene's mRNA. "To our surprise, these results indicate that a greater range of binding modes plays an important functional role for the gene regulation in T-cells," says Prof. Michael Sattler. "Thus, our findings suggest that Roquin regulates a larger number of genes than was previously assumed," Dr. Niessing adds. In addition to the mRNAs with optimal recognition motifs, which are tightly bound and predominantly regulated by Roquin, there is a potentially much larger number of mRNAs which are more weakly bound, but nevertheless regulated by Roquin. "On the basis of these findings we will now focus on understanding how Roquin levels are regulated in T-cells, since strong and weakly bound target mRNAs will experience a principally different regulation when the availability of the protein varies" explains Prof. Vigo Heissmeyer.
Basis for developing treatment
Defining the molecular interplay between Roquin and RNA is a prerequisite for con-trolling the function of Roquin and using its role for therapeutic strategies to treat autoimmune diseases. To this end, the scientists are now planning follow-up studies to find out how the function of Roquin can be manipulated.
*Autoimmune diseases occur when the immune system is activated to launch a response against normal body tissues and to treat them like a pathogen. In the process, the tissue is then damaged or destroyed, In the case of Type 1 diabetes, for example, an immune reaction is triggered to attack the insulin-producing cells in the pancreas. In the case of lupus, almost any part of the body can be attacked by the immune system.
Schlundt A. et al. (2014). Structural basis for RNA recognition in roquin-mediated post-transcriptional gene regulation, Nat Struct Mol Biol nähere Angaben bitte noch einfügen, doi:10.1038/nsmb.2855
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Institute for Structural Biology (STB) investigates the spatial structures of biological macromolecules, their molecular interactions and dynamics using integrated structural biology by combining X-ray crystallography, NMR-spectroscopy and other methods. Researchers at STB also develop NMR spectroscopy methods for these studies. The goal is to unravel the structural and molecular mechanisms underlying biological function and their impairment in disease. The structural information is used for the rational design and development of small molecular inhibitors in combination with chemical biology approaches. http://www. Media contacts
Communications Dept., Helmholtz Zentrum München - Deutsches Forschungszentrum für Gesundheit und Umwelt (GmbH), Ingolstaedter Landstr. 1, D-85764 Neuherberg - Tel.: +49 89-3187-2238 - Fax: +49 89-3187-3324 - e-mail: firstname.lastname@example.org
Vigo Heissmeyer,Dept. of Molecular Immune Regulation, Institute of Molecular Immunology, Tel.: +49 89 3187 1214, Fax: +49 89 3187-1300, e-mail: email@example.com
Dierk Niessing, Intracellular Transport and RNA Biology Group, Institute for Structural Biology, Tel.: +49 89 3187-2176, e-mail: firstname.lastname@example.org
Michael Sattler, Institute for Structural Biology, Tel: +49 89 3187-3800, Fax: +49 89 28913869, e-mail: email@example.com Helmholtz Zentrum München - Deutsches Forschungszentrum für Gesundheit und Umwelt (GmbH), Ingolstaedter Landstr. 1, D-85764 Neuherberg