USP7 represses lineage differentiation genes of mouse embryonic stem cells through both catalytic and non-catalytic activity

USP7, a ubiquitin-specific peptidase (USP), plays an important role in many cellular processes through its catalytic deubiquitination of various substrates. However, its nuclear function to regulate gene expression in mouse embryonic stem cells (mESCs) remains largely unknown. Here, we report that USP7 maintains mESCs identity through both catalytic activity-dependent and -independent repression of lineage differentiation genes. Usp7 depletion attenuates SOX2 level and derepresses lineage differentiation genes thereby compromising mESCs identity. Mechanistically, USP7 deubiquitinates and stabilizes SOX2 to repress mesoendodermal (ME) lineage genes. Moreover, USP7 assembles into RYBP-variant polycomb repressive complex 1 (vPRC1) and contributes to Polycomb chromatin domain-mediated repression of ME lineage genes in a catalytic activity-dependent manner. However, USP7 deficient in its deubiquitination function is able to maintain RYBP binding on chromatin to represses primitive endoderm-associated genes in mESCs. Overall, our study demonstrates that USP7 harbors both catalytic and non-catalytic scaffold activity to repress lineage differentiation genes thereby revealing a previously unrecognized role in controlling gene expression and maintaining mESCs identity. mRNA profiles of mESCs with auxin inducible degradation to rapidly deplete Usp7 protein, and overexpressed a Usp7 with HA-C224S enzyme catalytic center mutation (HA-C224S) and a HA-Usp7 wild type full length (HA-Usp7-FL) after IAA addition for 3 days mRNA profiles of mESCs transfected with shRNA lentiviruses for Usp7 and vector (Negtive control) after 7 days.