PMID: 29610493

Authors:

Luo F, Gui X, Zhou H, Gu J, Li Y, Liu X, Zhao M, Li D, Li X, Liu C

Title:

Atomic structures of FUS LC domain segments reveal bases for reversible amyloid fibril formation.

Journal:

Nat Struct Mol Biol. 2018 Apr;25(4):341-346. doi: 10.1038/s41594-018-0050-8. Epub, 2018 Apr 2.

Abstract:

Thermostable cross-beta structures are characteristic of pathological amyloid fibrils, but these structures cannot explain the reversible nature of fibrils formed by RNA-binding proteins such as fused in sarcoma (FUS), involved in RNA granule assembly. Here, we find that two tandem (S/G)Y(S/G) motifs of the human FUS low-complexity domain (FUS LC) form reversible fibrils in a temperature- and phosphorylation-dependent manner. We named these motifs reversible amyloid cores, or RAC1 and RAC2, and determined their atomic structures in fibrillar forms, using microelectron and X-ray diffraction techniques. The RAC1 structure features an ordered-coil fibril spine rather than the extended beta-strand typical of amyloids. Ser42, a phosphorylation site of FUS, is critical in the maintenance of the ordered-coil structure, which explains how phosphorylation controls fibril formation. The RAC2 structure shows a labile fibril spine with a wet interface. These structures illuminate the mechanism of reversible fibril formation and dynamic assembly of RNA granules.