Oestrogen controls Foxp3 expression in regulatory T cells (Treg cells) via a mechanism thought to involve oestrogen receptor alpha (ERα), but the molecular basis and functional impact of ERα signalling in Treg cells remain unclear. We report that ERα ligand oestradiol (E2) is significantly increased in human cervical cancer (CxCa) tissues and tumour-infiltrating Treg cells (CD4+CD25hiCD127low), whereas blocking ERα with the antagonist ICI 182,780 abolishes FOXP3 expression and impairs the function of CxCa infiltrating Treg cells. Using a novel approach of co-immunoprecipitation with antibodies to E2 for capture, we identified binding of E2:ERα complexes to FOXP3 protein in CxCa-derived Treg cells. Chromatin immunoprecipitation analyses of male blood Treg cells revealed ERα occupancy at the FOXP3 promoter and conserved non-coding DNA elements 2 and 3. Accordingly, computational analyses of the enriched regions uncovered eight putative oestrogen response elements predicted to form a loop that can activate the FOXP3 promoter. Together, these data suggest that E2-mediated ERα signalling is critical for the sustenance of FOXP3 expression and Treg cell function in human CxCa via direct interaction of ERα with FOXP3 promoter. Overall, our work gives a molecular insight into ERα signalling and highlights a fundamental role of E2 in controlling human Treg cell physiology.

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Viruses use miRNAs to enable efficient replication, control host defense mechanisms, and regulate latent infection. Herpes simplex virus 1 (HSV-1) expresses multiple miRNAs, whose functions are largely unknown. The evolutionary conservation of many HSV-1 miRNAs in the closely related HSV-2 suggests their functional importance. miRNAs, similar to other transcripts, can undergo various posttranscriptional modifications that may affect their biogenesis, stability and targeting. To investigate whether ADAR mediated editing occurs in HSV-1 miRNAs, we sequenced samples from latently infected human ganglia. We show that one of the six HSV-1 miRNAs (miR-H2-H8) that define HSV-1 latency, miR-H2, exhibits A-to-I hyperediting within the miRNA seed sequence. We observed the same specific miR-H2 hyperediting phenomenon in miRNAs isolated from the ganglia of latently infected mice and, to a lesser extent, during productive infection in cultured cells. Curiously, we found no evidence of editing of the encoded HSV-2 homolog in latently infected mice or in cultured cells. The efficient loading of the edited miRNAs onto the RISC complex, indicates their ability to function as miRNAs. Therefore, to investigate the potential of the edited miRNA to alter mRNA targeting, we predicted the host and viral targets. Nucleotide substitution in the seed region significantly increased the number of potential host and viral targets. Most notably, ICP4, an essential viral protein, was predicted to be an additional target. Using transfection assays, we demonstrated that edited miRNAs have the potential to regulate ICP4 in addition to the previously identified target ICP0. Our study identifies a specific hyperedited HSV-1 mRNA, miR-H2, and highlights how the virus can use a single miRNA to target multiple transcripts during persistent, latent infection.