Low-complexity (LC) domains of RNA-binding proteins are important for their protein functions, including gene expression and mRNA processing. Liquid-liquid phase separation (LLPS) is a process that underlies the formation of intracellular membrane-less organelles and is mediated by LC domains. However, aberrant aggregation of LC domains into amyloid fibrils, which may occur within phase-separated liquid droplets, is known to be connected to neurodegenerative diseases such as ALS and FTD. Interestingly, unlike other pathological amyloid-forming proteins such as Aβ and α-synuclein, LC domains are relatively devoid of hydrophobic residues, which play important roles in stabilizing the amyloid fibril core. Thus, it is largely unknown how LC domains form amyloid fibrils. Recently, the molecular structure of fibrils formed by the 214-residue LC domain of the fused in sarcoma (FUS) RNA-binding protein (FUS-LC) was determined using solid-state NMR (ssNMR)1. Despite the simple and repetitive amino acid composition, the FUS-LC fibril core is formed by a segment of 57-residues from the N-terminal region, while the C-terminal half region remains highly flexible. However, surprisingly, we found that the C-terminal half FUS-LC (FUS-dN8) forms fibrils when the N-terminal half region is truncated. How does the C-terminal half region form fibrils without the N-terminal fibril core? In order to answer this question, we are using ssNMR and cryoEM to characterize the FUS-dN8 fibril structure at atomic resolution. 2D and 3D ssNMR spectra and cryoEM images indicate that the core of FUS-dN8 fibrils contains fewer than 50 amino acid residues from the 104-residue FUS-dN8 sequence. 2D INEPT spectra measured under solution NMR conditions show strong cross-peaks, confirming that certain segments of FUS-dN8 are dynamic. In ongoing experiments, additional NMR measurements using segmentally 15N,13C-labeled FUS-dN8 fibrils and further refinement of the cryoEM data analysis will produce a full molecular structural model, revealing how these fibrils are formed and stabilized on the molecular level. The latest results from this project will be presented.

FUS low complexity (LC) domain fibril structure by solid-state NMR and cryo-electron microscopy

Macromolecular Chemistry: The Second Century

[Author Benefits](https://scimeetings.acs.org/?utm_source=pubs_content_marketing&utm_medium=website&utm_campaign=0320_MCF_NPI_Launch_Spring_Homepage&ref=pubs_content_marketing)

[How to use SciMeetings](https://storage.googleapis.com/dl.morressier.com/acs/SciMeetings-ACSSpring2020-HowToGuide_M3020-Final.pdf)

[Frequently Asked Questions](https://storage.googleapis.com/dl.morressier.com/acs/SciMtng_ACSNMSp2020_FAQ_M3120_Final.pdf)

ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.