Phase Separation of FUS with Poly(ADP-ribosyl)ated PARP1 Is Controlled by Polyamines, Divalent Metal Cations, and Poly(ADP-ribose) Structure.

Fused in sarcoma (FUS) is involved in the formation of nuclear biomolecular condensates associated with poly(ADP-ribose) [PAR] synthesis catalyzed by a DNA damage sensor such as PARP1. Here, we studied FUS microphase separation induced by poly(ADP-ribosyl)ated PARP1 [PAR-PARP1] or its catalytic variants PARP1 and PARP1, respectively, synthesizing (short PAR)-PARP1 or (short hyperbranched PAR)-PARP1 using dynamic light scattering, fluorescence microscopy, turbidity assays, and atomic force microscopy. We observed that biologically relevant cations such as Mg, Ca, or Mn or polyamines (spermine or spermidine) were essential for the assembly of FUS with PAR-PARP1 and FUS with PAR-PARP1 in vitro.

RNA and the RNA-binding protein FUS act in concert to prevent TDP-43 spatial segregation.

FUS and TDP-43 are two self-adhesive aggregation-prone mRNA-binding proteins whose pathological mutations have been linked to neurodegeneration. While TDP-43 and FUS form reversible mRNA-rich compartments in the nucleus, pathological mutations promote their respective cytoplasmic aggregation in neurons with no apparent link between the two proteins except their intertwined function in mRNA processing. By combining analyses in cellular context and at high resolution in vitro, we unraveled that TDP-43 is specifically recruited in FUS assemblies to form TDP-43-rich subcompartments but without reciprocity.

Using the structural diversity of RNA: protein interfaces to selectively target RNA with small molecules in cells: methods and perspectives.

In recent years, RNA has gained traction both as a therapeutic molecule and as a therapeutic target in several human pathologies. In this review, we consider the approach of targeting RNA using small molecules for both research and therapeutic purposes. Given the primary challenge presented by the low structural diversity of RNA, we discuss the potential for targeting RNA: protein interactions to enhance the structural and sequence specificity of drug candidates.

FUS RRM regulates poly(ADP-ribose) levels after transcriptional arrest and PARP-1 activation on DNA damage.

PARP-1 activation at DNA damage sites leads to the synthesis of long poly(ADP-ribose) (PAR) chains, which serve as a signal for DNA repair. Here we show that FUS, an RNA-binding protein, is specifically directed to PAR through its RNA recognition motif (RRM) to increase PAR synthesis by PARP-1 in HeLa cells after genotoxic stress. Using a structural approach, we also identify specific residues located in the FUS RRM, which can be PARylated by PARP-1 to control the level of PAR synthesis.

FUS fibrillation occurs through a nucleation-based process below the critical concentration required for liquid-liquid phase separation.

FUS is an RNA-binding protein involved in familiar forms of ALS and FTLD that also assembles into fibrillar cytoplasmic aggregates in some neurodegenerative diseases without genetic causes. The self-adhesive prion-like domain in FUS generates reversible condensates via the liquid-liquid phase separation process (LLPS) whose maturation can lead to the formation of insoluble fibrillar aggregates in vitro, consistent with the appearance of cytoplasmic inclusions in ageing neurons. Using a single-molecule imaging approach, we reveal that FUS can assemble into nanofibrils at concentrations in the nanomolar range.