Classification of Higher Order Assemblies of FUS and Their Role in Amyotrophic Lateral Sclerosis

Abstract

Mutations in the nuclear RNA-binding protein Fused in Sarcoma (FUS) gene are responsible for 5% of inherited ALS and 1% of spontaneously acquired ALS. FUS proteins contain an intrinsically disordered low complexity (LC) domain. This domain allows the protein to reversibly self-assemble, undergoing phase transition into condensates. This FUS assembly occurs in an RNA-dependent manner, showing little RNA specificity. These assemblies can then bind the CTD of RNA polymerase II and affect transcription. Mutations within the LC domain of FUS can lead to altered assembly formation. It can also cause protein mislocalization to the cytoplasm. We performed experiments to understand more about both mutagenic and wild type FUS, as there is still much that is unknown. We created mutant primers to establish a library of recombinant FUS plasmids. Each of these primers targeted a tyrosine residue in the LC domain. We also used dynamic light scattering (DLS) to investigate the size and structure of monomeric full length, wild-type FUS. Finally, we performed DLS assays on the FUS to induce assembly formation. These assays allowed for an investigation of both FUS-FUS and FUS-RNA interactions in vitro.