Genes Dev. 2019 Jun 1;33(11-12):669-683. doi: 10.1101/gad.322024.118. | PubMed

Charles Ng¹, Martin Aichinger², Tung Nguyen¹, Christy Au¹, Tariq Najar¹, Lin Wu¹, Kai R Mesa¹, Will Liao³, Jean-Pierre Quivy⁴, Benjamin Hubert³, Genevieve Almouzni⁴, Johannes Zuber², Dan R Littman^1,5

1. The Kimmel Center for Biology and Medicine of the Skirball Institute, New York University School of Medicine, New York, New York 10016, USA.
2. Research Institute of Molecular Pathology (IMP), Vienna BioCenter (VBC), 1030 Vienna, Austria.
3. New York Genome Center, New York, New York 10013, USA.
4. UMR3664, Centre National de la Recherche Scientifique, Equipe Labellisée Ligue Contre le Cancer, Institut Curie, PSL Research University, F-75005 Paris, France.
5. Howard Hughes Medical Institute, New York, New York 10016, USA.

Abstract

The transcriptional repression of alternative lineage genes is critical for cell fate commitment. Mechanisms by which locus-specific gene silencing is initiated and heritably maintained during cell division are not clearly understood. To study the maintenance of silent gene states, we investigated how the Cd4 gene is stably repressed in CD8+ T cells. Through CRISPR and shRNA screening, we identified the histone chaperone CAF-1 as a critical component for Cd4 repression. We found that the large subunit of CAF-1, Chaf1a, requires the N-terminal KER domain to associate with the histone deacetylases HDAC1/2 and the histone demethylase LSD1, enzymes that also participate in Cd4 silencing. When CAF-1 was lacking, Cd4 derepression was markedly enhanced in the absence of the de novo DNA methyltransferase Dnmt3a but not the maintenance DNA methyltransferase Dnmt1. In contrast to Dnmt1, Dnmt3a deficiency did not significantly alter levels of DNA methylation at the Cd4 locus. Instead, Dnmt3a deficiency sensitized CD8+ T cells to Cd4 derepression mediated by compromised functions of histone-modifying factors, including the enzymes associated with CAF-1. Thus, we propose that the heritable silencing of the Cd4 gene in CD8+ T cells exploits cooperative functions among the DNA methyltransferases, CAF-1, and histone-modifying enzymes.

Presented by Charles Ng