Functional analysis of the TTF complex and its role in neurodevelopmental diseases

• Applicant: Professor Dr. Utz Fischer
• Subject Area: General Genetics and Functional Genome Biology ; Molecular Biology and Physiology of Neurons and Glial Cells ; Cell Biology
• Term: from 2015 to 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 271023333

• Final Report Year: 2021

Final Report Abstract

Topoisomerases are enzymes that act predominantly, if not exclusively, on DNA substrates in cells of all kingdoms. It was therefore a surprise when we could show that eukaryotic topoisomerase TOP3ß is a cytosolic RNA binding protein that exhibits enzymatic activity on RNA substrates in vitro. It was further revealed that TOP3ß forms together with TDRD3, a scaffolding protein, and FMRP, affected in Fragile X mental retardation syndrome (FXS) an as yet unknown trimeric complex in vivo. In this project we have elucidated the role of this unit, which we have named TOP3ß-TDRD3-FMRP (TTF)- complex in RNA metabolism by identifying its RNA targets in vivo and determining its catalytic and/or regulatory function in RNA metabolism. We showed that the TTF complex is recruited to mRNPs via the exon junction complex (EJC) in a sequence independent manner. The biochemical composition of TTF-containing mRNPs and their association with polysomes further suggests that they are engaged in the pioneer round of translation. These studies also helped to shed light on a potential RNA-based etiology of neuropsychiatric disorders. In addition, we investigated the cellular functions of the La-related protein Larp4B, as well as the helicase IGHMBP2, linked to the neuromuscular disorder DSMA1. Both proteins were shown to interact with specific sets of cellular mRNA targets and regulate their translational output.

Publications

• „Untersuchung zur Rolle des La-verwandten Proteins LARP4B im mRNA-Metabolismus“
  Maritta Küspert
  
• Accumulated common variants in the broader fragile X gene family modulate autistic phenotypes (2015). EMBO molecular medicine 7 (12), 1565-1579
  Stepniak, Beata; Kästner, Anne; Poggi, Giulia; Mitjans, Marina; Begemann, Martin; Hartmann, Annette; Van der Auwera, Sandra; Sananbenesi, Farahnaz; Krueger‐Burg, Dilja; Matuszko, Gabriela; Brosi, Cornelia; Homuth, Georg; Völzke, Henry; Benseler, Fritz; Bagni, Claudia; Fischer, Utz; Dityatev, Alexander; Grabe, Hans‐Jörgen; Rujescu, Dan; ... & Ehrenreich, Hannelore
  
• LARP4B is an AU-rich sequence associated factor that promotes mRNA accumulation and translation (2015). RNA 21 (7), 1294-1305
  Küspert, Maritta; Murakawa, Yasuhiro; Schäffler, Katrin; Vanselow, Jens T.; Wolf, Elmar; Juranek, Stefan; Schlosser, Andreas; Landthaler, Markus & Fischer, Utz
  
• mRNA metabolism and neuronal disease (2015). FEBS Letters 589 (14), 1598-1606
  Linder, Bastian; Fischer, Utz & Gehring, Niels H.
  
• ProteoPlex: stability optimization of macromolecular complexes by sparse-matrix screening of chemical space (2015). Nature Methods 12 (9), 859-865
  Chari, Ashwin; Haselbach, David; Kirves, Jan-Martin; Ohmer, Juergen; Paknia, Elham; Fischer, Niels; Ganichkin, Oleg; Möller, Vanessa; Frye, Jeremiah J; Petzold, Georg; Jarvis, Marc; Tietzel, Michael; Grimm, Clemens; Peters, Jan-Michael; Schulman, Brenda A; Tittmann, Kai; Markl, Jürgen; Fischer, Utz & Stark, Holger
  
• Loss of LARP4B, an early event in the tumorigenesis of brain cancer? (2016). Translational Cancer Research 5 (S6)
  Blagden, Sarah; Schneider, Cornelius & Fischer, Utz
  
• Deciphering the mRNP code: RNA-bound determinants of post-transcriptional gene regulation (2017). TIBS 42 (5), 369-382
  Gehring, Niels H.; Wahle, Elmar & Fischer, Utz
  
• „Functional characterization of the TTF complex and its role in neurodevelopmental disorders “
  Cornelia Brosi
  
• Impaired local translation of β-actin mRNA in Ighmbp2-deficient motoneurons: implications for spinal muscular atrophy with respiratory distress (SMARD1) (2018). Neuroscience 386, 24-40
  Surrey, Verena; Zöller, Caren; Lork, Alicia Andrea; Moradi, Mehri; Balk, Stefanie; Dombert, Benjamin; Saal-Bauernschubert, Lena; Briese, Michael; Appenzeller, Silke; Fischer, Utz & Jablonka, Sibylle
  
• Crystal Structure of a Variant PAM2 Motif of LARP4B Bound to the MLLE Domain of PABPC1 (2020). Biomolecules 10 (6), 872
  Grimm, Clemens; Pelz, Jann-Patrick; Schneider, Cornelius; Schäffler, Katrin & Fischer, Utz
  
• The SARS-CoV-2 RNA–protein interactome in infected human cells (2020). Nature Microbiology, 1-15
  Schmidt, Nora; Lareau, Caleb A.; Keshishian, Hasmik; Ganskih, Sabina; Schneider, Cornelius; Hennig, Thomas; Melanson, Randy; Werner, Simone; Wei, Yuanjie; Zimmer, Matthias; Ade, Jens; Kirschner, Luisa; Zielinski, Sebastian; Dölken, Lars; Lander, Eric S.; Caliskan, Neva; Fischer, Utz; Vogel, Jörg; Carr, Steven A.; ... & Munschauer, Mathias