SPATA2 restricts OTULIN-dependent LUBAC activity independently of CYLD.

SPATA2 mediates the recruitment of CYLD to immune receptor complexes by bridging the interaction of CYLD with the linear ubiquitylation assembly complex (LUBAC) component HOIP. Whether SPATA2 exhibits functions independently of CYLD is unclear. Here, we show that, while Cyld-/- and Spata2-/- mice are viable, double mutants exhibit highly penetrant perinatal lethality, indicating independent functions of SPATA2 and CYLD. Cyld-/- Spata2-/- fibroblasts show increased M1-linked TNFR1-SC ubiquitylation and, similar to Cyld-/- Spata2-/- macrophages and intestinal epithelial cells, elevated pro-inflammatory gene expression compared with Cyld-/- or Spata2-/- cells. We show that SPATA2 competes with OTULIN for binding to HOIP via its PUB-interacting motif (PIM) and its zinc finger domain, thereby promoting autoubiquitylation of LUBAC. Consistently, increased pro-inflammatory signaling in Cyld-/- Spata2-/- cells depends on the presence of OTULIN. Our data therefore indicate that SPATA2 counteracts, independently of CYLD, the deubiquitylation of LUBAC by OTULIN and thereby attenuates LUBAC activity and pro-inflammatory signaling.