ZBP1 condensate formation synergizes Z-NAs recognition and signal transduction.

Z-DNA binding protein 1 (ZBP1) is a crucial player in the intracellular recognition of Z-form nucleic acids (Z-NAs) through its Zαβ domain, initiating downstream interactions with RIPK1 and RIPK3 via RHIM domains. This engagement leads to the assembly of PANoptosomes, ultimately inducing programmed cell death to curb pathogen dissemination. How Zαβ and RHIM domain cooperate to trigger Z-NAs recognition and signal transduction remains unclear. Here, we show that ZBP1 condensate formation facilitates Z-NAs binding and antiviral signal transduction. The ZBP1 Zαβ dimerizes in a concentration-dependent manner, forming characteristic condensates in solutions evidenced by DLS and SAXS methods. ZBP1 exhibits a binding preference for 10-bp length CG (10CG) DNA and Z-RNA ligand, which in turn enhanced Zαβ dimerization, expediting the formation of droplet condensates in vitro and amyloid-like puncta in cells. Subsequent investigations reveal that Zαβ could form condensates with liquid-liquid phase separation property upon HSV and IAV infections, while full-length ZBP1 forms amyloid-like puncta with or without infections. Furthermore, ZBP1 RHIM domains show typical amyloidal fibril characterizations and cross-polymerize with RIPK1 depending on the core motif of 206 IQIG 209 , while mutated ZBP1 could impede necroptosis and antiviral immunity in HT-29 cells. Thus, ZBP1 condensate formation facilitates the recognition of viral Z-NAs and activation of downstream signal transduction via synergic action of different domains, revealing its elaborated mechanism in innate immunity.