The SGYS motif of TAF15 prion-like domain is critical to amyloid fibril formation.

Misfolding of TATA-box binding protein-associated factor 15 (TAF15) may cause neurodegenerative diseases, such as amyotrophic lateral sclerosis (ALS). Some mutations of prion-like domain (PrLD) have been detected in patients with sporadic ALS, suggesting the importance of TAF15-PrLD in ALS pathogenesis. Herein, combining experiments and molecular dynamics (MD) simulations, we investigated the influences of several TAF15-PrLD mutations on the amyloid fibril formation of TAF15-PrLD-extracted peptide segments, and identified an essential β-amyloid-forming segment from TAF15-PrLD. A pathogenic mutation T2 E71G resulted in significantly enhanced aggregation of the TAF15-PrLD segment T2 (Y56GQSQSGYSQSYGGYENQ73). In addition, the peptide T2 with a strong β-amyloid-forming tendency was able to induce the liquid to solid phase transition of TAF15-PrLD protein. Further study identified the SGYS motif as a critical segment that promoted the formation of amyloid fibrils, which maintained a stable β-sheet structure through intermolecular hydrogen bonds and π-π stacking interaction. This work provides a clue to elucidate the molecular pathogenic mechanism of TAF15-associated neurodegenerative diseases, and will direct drug development targeting TAF15.