Modulation of activated T cells by transient EZH2 inhibition [RNA-Seq]

The histone methyltransferase enhancer of zeste homolog 2 (EZH2)-mediated epigenetic regulation of T cell differentiation in acute infection has been extensively investigated. However, the role of EZH2 in T cell exhaustion remains under-explored. Here, using in vitro exhaustion models, we demonstrate that transient inhibition of EZH2 in T cells prior to the phenotypic onset of exhaustion with a clinically approved inhibitor, Tazemetostat, delays their dysfunctional progression and preserves T cell stemness and polyfunctionality while having no negative impact on cell proliferation. Tazemetostat induces T-cell epigenetic reprogramming and increases the expression of the self-renewal T cell transcription factor TCF1 by reducing its promoter H3K27 methylation preferentially in rapidly dividing T cells. Transcriptomic profiling revealed a cell division-dependent upregulation of genes associated with thymocytes, memory and effector T cell subsets. Mapping of EZH2-associated genomic regions by ChIP-seq showed an enrichment of promoters among H2K27me3 loci reduced in abundance by tazemetostat, including those genes upregulated in taz-treated T cells. OT-I splenocytes were activated with OVA257-264 (SIINFEKL, 500 nM) with 60 IU/mL of IL-2 for three days to obtain CD8+ T cells. The cells were further cultured with or without 1 µM Taz for 24 or 48 h before they are harvested for RNA extraction with the Arcturus™ PicoPure™ RNA Isolation Kit (KIT0204, ThermoFisher Scientific). Traces of genomic DNA were removed using RNase-Free DNase Set (79254, QIAGEN) following the on-column digesting protocol of the RNA isolation kit. Library construction and RNAseq data acquisition was done by the Novogene Corporation (Sacramento, CA) using Illumina HiSeq platform and PE150 strategy.