Molecular mechanisms of Id2 down-regulation in rat liver after acetaminophen overdose. Protection by N-acetyl-L-cysteine

Abstract

Id2 is a pleiotropic protein whose function depends on its expression levels. Id2-deficient cells show increased cell death. This study explored the molecular mechanisms for the modulation of Id2 expression elicited by GSH and oxidative stress in the liver of acetaminophen (APAP)-intoxicated rats. APAP-overdose induced GSH depletion, Id2 promoter hypoacetylation, RNApol-II released and, therefore, Id2 down-regulation. Id2 expression depends on c-Myc binding to its promoter. APAP-overdose decreased c-Myc content and binding to Id2 promoter. Reduction of c-Myc was not accompanied by decreased c-myc mRNA, suggesting a mechanism dependent on protein stability. Administration of N-acetyl-cysteine prior to APAP-overload prevented GSH depletion and c-Myc degradation. Consistently, c-Myc was recruited to Id2 promoter, histone-H3 was hyperacetylated, RNApol II was bound to Id2 coding region and Id2 repression prevented. The results suggest a novel transcriptional-dependent mechanism of Id2 regulation by GSH and oxidative stress induced by APAP-overdose through the indirect modulation of the proteasome pathway.