Alvarez-Errico, D. | Search bioRxiv

bioRxiv2023

The catalytic-independent function of LSD1 modulates the epigenetic landscape of mouse embryonic stem cells

Lysine-specific histone demethylase 1 (LSD1), which demethylates mono- or di-methylated histone H3 on lysine 4 (H3K4me1/2), is essential for early embryogenesis and development. Here we show that LSD1 is dispensable for embryonic stem cell (ESC) self-renewal but is required for ESC growth and differentiation. Reexpression of a catalytically-dead LSD1 (LSD1MUT) recovers the proliferation capability of ESCs, yet the enzymatic activity of LSD1 is essential to ensure proper differentiation. Indeed, a gain of H3K4me1 in Lsd1 knockout (KO) ESCs does not lead to major changes in global gene expression programs related to stemness. However, ablation of LSD1 but not LSD1MUT results in decreased DNMT1 and UHRF1 proteins coupled to global hypomethylation. We show that both LSD1 and LSD1MUT control protein stability of UHRF1 and DNMT1 through interaction with the ubiquitin-specific peptidase 7 (USP7) and, consequently, inhibiting DNMT1 and UHRF1 ubiquitylation. Our studies elucidate for the first time a novel mechanism by which the scaffolding function of LSD1 controls DNA methylation in ESCs.

molecular biology↗

bioRxiv2020

The JAK2-STAT pathway epigenetically regulates tolerized genes during the first encounter with bacterial antigens

Microbial challenges, such as widespread bacterial infection, induce endotoxin tolerance. This state of hyporesponsiveness to subsequent infections is mainly displayed by monocytes and macrophages. Endotoxin tolerance is generally acquired following a septic episode. In this study, we investigated DNA methylation changes during the acquisition of in vitro tolerance. We identified a set of TET2-mediated demethylation events that are specific to toll-like receptor (TLR) 2 and TLR4 stimulation. Lipopolysaccharide (LPS)-specific demethylation occurs at genomic sites that have low accessibility in quiescent monocytes, concomitantly with the transcriptional activation of many inflammation-related genes, and they are enriched in binding motifs for several signal transducer and activator of transcription (STAT) family members. Indeed, STAT1, STAT3 and STAT5, elements of the JAK2 pathway, are phosphorylated in association with the acquisition of endotoxin tolerance. Inhibition of the JAK2 pathway impairs the activation of tolerized genes on the first encounter with LPS. This is evidence of a crucial role for this pathway in determining the initial response of these genes to bacterial antigens and provides a pharmacological target to prevent exacerbated responses, allowing regulated responses upon subsequent challenges. Finally, we assess the pathological relevance of the JAK2 pathway in monocytes from patients with sepsis.

immunology↗