The Structural Basis for RNA Binding and Recognition of the Disordered Prion-Like Domain of TDP-43

Though the structural details of how RNA interacts with folded RNA-binding domains are well established, how intrinsically disordered regions (IDRs) found in a large fraction of RNA-binding proteins mediate contacts with RNA and if they contribute to binding specificity has not been extensively characterized. The human RNA-binding protein TDP-43 is associated with many RNA processing functions that require its predominantly disordered C-terminal domain (CTD) that forms disease-associated inclusions in ALS, and other neurodegenerative conditions. Here, we demonstrate that TDP-43 CTD directly interacts with RNA primarily via a region of the IDR composed of clustered positively charged residues. Large RNAs act as a multivalent scaffold for CTD monomers, inducing the -helical segment of TDP-43 CTD to form multimeric protein-protein structures. Additionally, we probe the nucleotide base and amino acid specificity of CTD-RNA interactions, showing that arginine, aromatic and polar residues display a preference for U and G nucleic acid bases over C and A. Finally, we probe the molecular basis for the strong binding interaction between TDP-43 and G4 quadruplex structures and discover similarly avid interactions with cytosine-rich DNA I-motifs. This work deepens our understanding of how disordered regions of proteins contribute to RNA recognition, drive function, and contribute to disease. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=107 SRC="FIGDIR/small/695782v1_ufig1.gif" ALT="Figure 1"> View larger version (26K): org.highwire.dtl.DTLVardef@f1d256org.highwire.dtl.DTLVardef@284c2forg.highwire.dtl.DTLVardef@1a1d715org.highwire.dtl.DTLVardef@2fbb1a_HPS_FORMAT_FIGEXP M_FIG C_FIG