Gene expression analysis of wild type and KAP1 KO splenic B cells

Chromatin remodeling is fundamental for B cell differentiation. Here, we explored the role in this process of KAP1, the cofactor of KRAB-ZFP transcriptional repressors. B lymphoid-specific Kap1 knockout mice displayed reduced numbers of mature B cells, lower steady-state levels of antibodies and accelerated rates of decay of neutralizing antibodies following viral immunization. Transcriptome analyses of Kap1-deleted B splenocytes revealed an upregulation of PTEN, the enzymatic counter-actor of PIK3 signaling, and of genes encoding DNA damage response factors, cell-cycle regulators and chemokine receptors. ChIP/seq studies established that KAP1 bound at or close to a number of these genes, and controlled chromatin status at their promoters. Genome-wide, KAP1-binding sites avoided active B cell-specific enhancers and were enriched in repressive histone marks, further supporting a role for this molecule in gene silencing in vivo. Likely responsible for tethering KAP1 to at least some of these targets, a discrete subset of KRAB-ZFPs is enriched in B lymphocytes. This work thus reveals the role of KRAB/KAP1-mediated epigenetic regulation in B cell development and homeostasis.

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Santoni de Sio FR, Massacand J, Barde I, Offner S, Corsinotti A, Kapopoulou A, Bojkowska K, Dagklis A, Fernandez M, Ghia P, Thomas JH, Pinschewer D, Harris N, Trono D