An unexpected role for Dicer as a reader of the unacetylated DNA binding domain of p53 in transcriptional regulation

Here, we identified Dicer as a major cellular factor that recognizes the DNA binding domain (DBD) of p53 in a manner dependent on its acetylation status. Upon binding the unacetylated DBD, Dicer is recruited to the promoters of p53 target genes, where it represses p53-mediated transcriptional activation. Conversely, knockdown or knockout of endogenous Dicer leads to up-regulation of p53-mediated transcriptional activation without increasing its protein levels. Moreover, Dicer-mediated repression is independent of its intrinsic endoribonuclease activity; instead, Dicer directly represses transcription by recruiting the SUV39H1 histone methyltransferase. However, upon DNA damage, Dicer-mediated repression is abrogated by stress-induced acetylation at the DBD of p53. Notably, the inability of acetylation-defective p53-3KR in transcription is partially but significantly restored upon loss of Dicer expression. Our study reveals that Dicer acts as an unexpected acetylation “reader” for p53 and thus has important implications regarding the mechanism of acetylation-mediated regulation of p53 transcriptional program.