Inflammasome-activated caspase 7 cleaves PARP1 to enhance the expression of a subset of NF-κB target genes

Caspase 1 is part of the inflammasome, which is assembled upon pathogen recognition, while caspases 3 and/or 7 are mediators of apoptotic and nonapoptotic functions. PARP1 cleavage is a hallmark of Apoptosis yet not essential, suggesting it has another physiological role. Here we show that after LPS stimulation, Caspase 7 is activated by Caspase 1, translocates to the nucleus, and cleaves PARP1 at the promoters of a subset of NF-κB target genes negatively regulated by PARP1. Mutating the PARP1 cleavage site D214 renders PARP1 uncleavable and inhibits PARP1 release from chromatin and chromatin decondensation, thereby restraining the expression of cleavage-dependent NF-κB target genes. These findings propose an apoptosis-independent regulatory role for Caspase 7-mediated PARP1 cleavage in proinflammatory gene expression and provide insight into inflammasome signaling.