ABSTRACT
The role of chromatin-associated RNAi components in the nucleus of mammalian cells and in particular in the context of developmental programs remains to be elucidated. Here, we investigate the function of nuclear Argonaute 1 (Ago1) in gene expression regulation during skeletal muscle differentiation. We show that Ago1 is required for activation of the myogenic program by supporting chromatin modification mediated by developmental enhancer activation. Mechanistically, we demonstrate that Ago1 directly controls global H3K27 acetylation (H3K27ac) by regulating enhancer RNA (eRNA)-CREB-binding protein (CBP) acetyltransferase interaction, a key step in enhancer-driven gene activation. In particular, we show that Ago1 is specifically required for myogenic differentiation 1 (MyoD) and downstream myogenic gene activation, whereas its depletion leads to failure of CBP acetyltransferase activation and blocking of the myogenic program. Our work establishes a role of the mammalian enhancer-associated RNAi component Ago1 in epigenome regulation and activation of developmental programs.
Subject(s)
Argonaute Proteins/metabolism , Epigenome , Eukaryotic Initiation Factors/metabolism , Gene Expression Regulation , Histones/metabolism , Membrane Proteins/metabolism , Myoblasts/cytology , Phosphoproteins/metabolism , RNA, Untranslated/metabolism , Acetylation , Animals , Argonaute Proteins/genetics , Cell Differentiation , Cell Nucleus/genetics , Cell Nucleus/metabolism , Chromatin/genetics , Chromatin/metabolism , Enhancer Elements, Genetic , Eukaryotic Initiation Factors/genetics , Histones/genetics , Membrane Proteins/genetics , Mice , Muscle Development , Myoblasts/metabolism , Phosphoproteins/genetics , RNA, Untranslated/genetics , Transcription, GeneticABSTRACT
The impact of mammalian RNA interference components, particularly, Argonaute proteins, on chromatin organization is unexplored. Recent reports indicate that AGO1 association with chromatin appears to influence gene expression. To uncover the role of AGO1 in the nucleus, we used a combination of genome-wide approaches in control and AGO1-depleted HepG2 cells. We found that AGO1 strongly associates with active enhancers and RNA being produced at those sites. Hi-C analysis revealed AGO1 enrichment at the boundaries of topologically associated domains (TADs). By Hi-C in AGO1 knockdown cells, we observed changes in chromatin organization, including TADs and A/B compartment mixing, specifically in AGO1-bound regions. Distinct groups of genes and especially eRNA transcripts located within differentially interacting loci showed altered expression upon AGO1 depletion. Moreover, AGO1 association with enhancers is dependent on eRNA transcription. Collectively, our data suggest that enhancer-associated AGO1 contributes to the fine-tuning of chromatin architecture and gene expression in human cells.
