Dokument: Dissecting the binding behaviour of the multi-RRM protein Rrm4 during endosomal mRNA transport

Titel:	Dissecting the binding behaviour of the multi-RRM protein Rrm4 during endosomal mRNA transport
URL für Lesezeichen:	https://docserv.uni-duesseldorf.de/servlets/DocumentServlet?id=72537
URN (NBN):	urn:nbn:de:hbz:061-20260318-084033-2
Kollektion:	Dissertationen
Sprache:	Englisch
Dokumententyp:	Wissenschaftliche Abschlussarbeiten » Dissertation
Medientyp:	Text
Autor:	Stoffel, Nina Kim [Autor]
Dateien:	[Dateien anzeigen] Adobe PDF [Details] 50,25 MB in einer Datei [ZIP-Datei erzeugen] Dateien vom 12.03.2026 / geändert 12.03.2026
Beitragende:	Prof. Dr. Feldbrügge, Michael [Gutachter] Prof. Dr. Schaal, Heiner [Gutachter]
Dewey Dezimal-Klassifikation:	500 Naturwissenschaften und Mathematik » 570 Biowissenschaften; Biologie
Beschreibung:	Spatiotemporal gene regulation relies on RNA-binding proteins (RBPs) that coordinate mRNA transport and translation. Many RBPs feature modular architectures with multiple RNA-binding domains (RBDs), yet the domain-specific contributions to RNA and protein interactomes in vivo remain poorly understood. This thesis presents a systematic dissection of the binding behavior of Rrm4, the key RBP that mediates translation-active endosomal mRNA transport during polarized growth in the pathogen Ustilago maydis. To resolve the functions of its three RNA recognition motifs (RRMs), domain-specific mutants were analyzed through a multi-omics strategy combining iCLIP2 (individual-nucleotide resolution UV crosslinking and immunoprecipitation), differential RNA sequencing, endosome- and co-immunoprecipitation mass spectrometry (endo-IP MS, co-IP MS), and cell biological validation. RNA interactome profiling revealed that the tandem domains RRM1/2 recognize functionally important binding sites (RRM12-BS), which are required for mRNA transport and abundance. RRM12-BS are enriched in transcripts linked to polarity, mitochondrial activity, and cell wall plasticity—linking RNA binding to unipolar growth. In contrast, RRM3 enhances RNA affinity via sequence-specific UAUG binding but is largely dispensable for polarity establishment. Moreover, the endosomal proteome depends on Rrm4’s RNA-binding capacity. Mutation of RRM1/2 or deletion of Rrm4 selectively reduced endosome-associated proteins encoded by Rrm4-target mRNAs (e.g., polarity factors) and co-localized ribosomes, whereas neither RRM3 mutation nor proteins encoded by non-target mRNAs showed detectable changes. These findings point to a functional hierarchy among the RRMs, with RRM1/2 mediating endosomal mRNA hitchhiking and local translation, thereby shaping the endosomal proteome. Since RBPs rarely act in isolation, the RRM-dependent Rrm4 protein interactome was dissected. RRM1 mediates RNA-independent interactions with the mRNP scaffold protein Upa2 and the translational repressor Ssd1, positioning RRM1 as a multivalent hub that integrates RNA binding, mRNP assembly, and translational control. The Rrm4–Ssd1 interaction likely facilitates the repressed transport of cell wall–related mRNAs, highlighting a new regulon-specific model of translation-regulated endosomal mRNA trafficking. Beyond mRNAs, Rrm4 binds pre-tRNAs, expanding its interactome to non-coding RNAs. Pre-tRNAs co-localize with endosomes and are delivered to mitochondria, where intron removal occurs. Deletion of Rrm4 impairs splicing efficiency and global translation, revealing a novel link between endosomal transport and tRNA maturation. Together, this work defines how the multi-RRM RBP Rrm4 coordinates RNA and protein networks and expands the concept of endosomal RNA transport in space and time—from fungi to neurons.
Lizenz:	Dieses Werk ist lizenziert unter einer Creative Commons Namensnennung 4.0 International Lizenz
Fachbereich / Einrichtung:	Mathematisch- Naturwissenschaftliche Fakultät » WE Biologie » Mikrobiologie
Dokument erstellt am:	18.03.2026
Dateien geändert am:	18.03.2026
Promotionsantrag am:	14.08.2025
Datum der Promotion:	13.01.2026