ChIP-seq analysis of KAP1 binding and H3K9me3 modifications in mouse T cell progenitors. Mus musculus

Chromatin remodelling at specific genomic loci controls lymphoid differentiation. Here, we investigated the role played in this process by Kruppel-Associated Box (KRAB)- Associated Protein 1 (KAP1), the universal cofactor of KRAB-zinc finger proteins (-ZFPs), a tetrapod-restricted family of transcriptional repressors. T cell-specific Kap1-deleted mice displayed a significant expansion of immature thymocytes, imbalances in CD4+/CD8+ cell ratios and impaired responses to TCR stimulation when compared to littermate KAP1 control mice. Transcriptome and chromatin studies revealed that KAP1 binds T cell-specific cis-acting regulatory elements marked by the H3K9me3 repressive mark and enriched in Ikaros/NuRD complexes. Also, KAP1 directly controls the expression of several genes involved in TCR and cytokine signalling. Among these, regulation of FoxO1 seems to play a major role in this system. Likely responsible for tethering KAP1 to at least part of its genomic targets, a small number of KRAB-ZFPs are selectively expressed in T lymphoid cells. These results reveal the so-far unsuspected yet important role of KAP1-mediated epigenetic regulation in T lymphocyte differentiation and activation. Overall design: Examination of KAP1 binding sites and H3K9me3-enriched regions in wild type and KAP1 KO mouse thymocytes.