The regulatory role of Ctbp2-interacting zinc finger proteins, Zfp217 and Zfp516, in embryonic stem cell differentiation

Abstract

Transcription factors and chromatin remodeling proteins control the transcriptional variability for embryonic stem cell (ESC) lineage commitment. During ESC differentiation, chromatin modifiers are recruited to the regulatory regions by transcription factors, thereby activating the lineage-specific genes or silencing active ESC genes. On differentiation cue, active ESC genes are silenced by C-terminal binding protein 2 (Ctbp2) and its binding complexes, the nucleosome remodeling and deacetylation (NuRD) complex and the polycomb repressive complex 2 (PRC2), which each modify H3K27 deacetylation and tri-methylation mediated repression. However, Ctbp2 itself is unable to bind to the DNA, which leaves a missing link in Ctbp2-mediated epigenetic regulation during stem cell differentiation. Also, the underlying mechanisms that link transcription factors to the exit from pluripotency are not yet identified. Thus, it is necessary to search for transcription factors that fine-tune Ctbp2 and these epigenetic regulators on active ESC genes. In this study, we analyzed the role of the Ctbp2-interacting zinc finger proteins, Zfp217 and Zfp516, as linkers for the chromatin regulators during ESC differentiation. CRISPR-Cas9-mediated double knock-outs of both Zfp217 and Zfp516 in ESCs prevented the exit from pluripotency. Both zinc finger proteins cooperatively regulated the Ctbp2-mediated NuRD complex and PRC2 complex recruitment to active ESC genes, subsequently switching the H3K27ac to H3K27me3 during ESC differentiation. Therefore, we suggest that zinc finger proteins, Zfp217 and Zfp516, orchestrate with Ctbp2 to control the concise epigenetic states on active ESC genes during differentiation, resulting in natural lineage commitment.