Periodic Reporting for period 2 - RNPdynamics (Multivalent interactions driving RNP dynamics in development and disease)
Berichtszeitraum: 2021-07-01 bis 2022-12-31
Understanding the way how disordered regions contribute to RNA binding is essential in order to understand how mutations in these regions act, and how they initiate the early stages of molecular changes that eventually lead to neurodegeneration. To address this question, we proceeded along five objectives:
1. identifying the functions of disorder-containing RNA-binding proteins during stem cell differentiation.
2. Assessing the importance of multivalency of the bound RNA regions for the formation of protein-RNA condensates.
3. Manipulating protein-RNA assembly through multivalent RNA regions.
4. Manipulating the protein disorder-dependent assembly and dynamics of protein-RNA complexes.
5. Assessing the species-specific roles of multivalent protein-RNA complexes.
Most importantly, we addressed the long-standing question of whether TDP-43 condensation is required for its RNA binding specificity and function, and how this relies on multivalent features of bound RNA regions (Hallegger et al, Cell, 2021). We created variants of TDP-43 containing mutations in its disordered regions with a gradient of condensation properties as evident by in vitro phase separation, and by imaging the condensates of TDP-43 in cells. We then used comparative iCLIP to find that the condensation of TDP-43 is required for its efficient binding to specific, long RNA regions that are highly multivalent with dispersed binding motifs. Thereby, we could explain how the condensation propensity of TDP-43 affects regulation of a select subset of 3’UTR isoforms, including autoregulation of TDP-43 itself.