SPARCLE, a p53-induced lncRNA, controls apoptosis after genotoxic stress by promoting PARP-1 cleavage

p53, master transcriptional regulator of the genotoxic stress response, controls cell cycle arrest and apoptosis following DNA damage. Here we identify a p53-induced lncRNA SPARCLE (Suicidal PARP-1 Cleavage Enhancer) adjacent to miR-34b/c required for p53-mediated apoptosis. SPARCLE is a ~770 nucleotide, nuclear lncRNA induced one day after DNA damage. Despite low expression (<15 copies/cell), SPARCLE deletion increases DNA repair and reduces DNA damage-induced apoptosis as much as p53 deficiency, while its over-expression restores apoptosis in p53-deficient cells. SPARCLE does not alter gene expression. SPARCLE causes apoptosis by acting as a caspase-3 cofactor for PARP-1 cleavage, which separates its N-terminal (NT) DNA binding domain from PARP-1 catalytic domains. NT-PARP-1 binds to DNA breaks but, lacking its PARylation domains, does not initiate DNA repair. In fact, expressing NT-PARP-1 in SPARCLE-deficient cells increases unrepaired DNA damage and restores apoptosis after DNA damage. Thus, as a PARP-1 cleavage cofactor, SPARCLE enhances p53-induced apoptosis. Overall design: Strand-specific RNA-seq of HCT116 cells treated with doxorubicin (1 uM) or control media for 48h. Cells are WT, KO or Over-express SPARCLE. Two biological replicates per condition are sequenced