Inflammasome-Activated Caspase 7 Cleaves PARP1 to Enhance the Expression of a Subset of NF-κB Target Genes

SummaryCaspase 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.

► LPS causes NLRP3 and caspase 1 activation and nuclear translocation of caspase 7 ► Caspase 7 mediates nonapoptotic PARP1 cleavage at a subset of NF-κB target genes ► Upon cleavage at D214, both PARP1 fragments (p24, p89) dissociate from chromatin ► PARP1 chromatin release derepresses NF-κB target genes and enhances gene expression