2025 AIChE Annual Meeting

(604e) Molecular Determinants of TAF15 Phase Separation

Authors

Shuo-Lin Weng, Texas A&M University
TATA-box binding protein associated factor 15 (TAF15) is an RNA-binding protein (RBP) belonging to the Fused in Sarcoma (FUS) /Ewing Sarcoma (EWS) /TAF15 (FET) family. The FET family proteins are predominantly found in the nucleus and are essential for transcription and RNA processing but are also linked to neurodegenerative diseases through protein aggregation forming amyloid fibrils. These proteins share a conserved domain architecture consisting of intrinsically disordered regions (IDRs) and folded RNA-binding motifs. The FET family, like other RBPs, exhibits reversible liquid-liquid phase separation (LLPS) forming “membraneless organelles” commonly referred to as biomolecular condensates. In previous years the LLPS behavior of FUS has been extensively characterized, in part due to its clear connection to diseases such as amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration (FTLD). A recent study of FTLD positive brain samples found abundant TAF15 amyloid filaments rather than FUS. Although previously understudied, TAF15 and its associated LLPS behavior are essential to understand in order to elucidate their potential role in the pathological aggregation associated with FTLD.

To investigate TAF15’s LLPS behavior, we performed molecular dynamics (MD) simulations at coarse-grained and atomistic resolutions, with a particular focus on the contributions of its distinct IDRs. In coarse-grained phase coexistence simulations, TAF15 full-length (FL) exhibited a strong LLPS propensity, whereas its LC domain did not, contrary to the behavior of homologs. Additionally, we used all-atom MD simulations with Parallel Tempering in a Well-Tempered Ensemble to effectively sample FL TAF15’s conformational landscape and study the driving forces behind its LLPS behavior. Our results suggest that intradomain interactions between the LC and Arginine-Glycine rich 3 (RGG3) domains play a significant role in modulating LLPS. By establishing foundational insights into TAF15’s LLPS characteristics, we aim to contribute to the broader understanding of RBP condensates and their link to amyloid aggregation.