Poly (ADP-Ribose) Polymerase-1 (PARP-1) Induction by Cocaine Is Post-Transcriptionally Regulated by miR-125b

Abstract Cocaine exposure alters gene expression in the brain via methylation and acetylation of histones along with methylation of DNA. Recently, Poly (ADP-ribose) polymerase-1 (PARP-1) catalyzed PARylation has been reported as an important regulator of cocaine-mediated gene expression. In this study, we report that the cellular microRNA “miR-125b” plays a key role for cocaine-induced PARP-1 expression. Acute and chronic cocaine exposure resulted in the downregulation of miR-125b concurrent with upregulation of PARP-1 in dopaminergic neuronal cells and nucleus accumbens of mice but not in the medial prefrontal cortex or ventral tegmental area. In silico analysis predicted a binding site of miR-125b in a conserved 39-untranslated region (3’UTR) of the PARP-1 mRNA. Knockdown and overexpression studies showed that miR-125b levels negatively correlate with PARP-1 protein expression. Luciferase reporter assay using a vector containing the 3’UTR of PARP-1 mRNA confirmed regulation of PARP-1 by miR-125b. Specific nucleotide mutations within the binding site abrogated miR-125b’s regulatory effect on PARP-1 3’UTR. Finally, we established that downregulation of miR-125b and concurrent upregulation of PARP-1 is dependent on binding of cocaine to the dopamine transporter (DAT). Collectively, these results identify miR-125b as a post-transcriptional regulator of PARP-1 expression and establish a novel mechanism underlying the molecular effects of cocaine action. Significance Statement PARP-1 plays critical roles in neuronal function. Recently, PARP-1 and PARylation have been described as a novel regulator of cocaine addiction and reward. However, the cellular pathways and mechanisms that regulate PARP-1 expression in neurons are unknown. We have identified that the cellular miRNA “miR-125b” negatively regulates PARP-1 protein expression. In addition, we have established that cocaine-induced upregulation of PARP-1 is dependent on miR-125b expression. These results elucidate the mechanism of PARP-1 regulation by cocaine and uncover a novel pathway for the cellular and molecular effects of cocaine.