Polycomb group RING finger proteins 3/5 activate transcription via an interaction with the pluripotency factor Tex10 in embryonic stem cells

Abstract

Polycomb group (PcG) proteins are epigenetic transcriptional repressors that orchestrate numerous developmental processes and have been implicated in the maintenance of embryonic stem (ES) cell state. More recent evidence suggests that a subset of PcG proteins engages in transcriptional activation in some cellular contexts, but how this property is exerted remains largely unknown. Here, we generated ES cells with single or combined disruption of polycomb group RING finger protein 3 (Pcgf3) and Pcgf5 with the CRISPR-Cas9 technique. We report that although these mutant cells maintained their self-renewal and colony-forming capacity, they displayed severe defects in mesoderm differentiation and Using RNA-seq to analyze transcriptional profiles of ES cells with single or combined Pcgf3/5 deficiencies, we found that in contrast to the canonical role of the related polycomb repressive complex 1 (PRC1) in gene repression, Pcgf3/5 mainly function as transcriptional activators driving expression of many genes involved in mesoderm differentiation. Proteomic approaches and promoter occupancy analyses helped to establish an extended Pcgf3/5 interactome and identified several novel Pcgf3/5 interactors. These included testis-expressed 10 (Tex10), which may directly contribute to transcriptional activation via the transcriptional co-activator p300. Furthermore, Pcgf3/5 deletion in ES cells substantially reduced the occupancy of Tex10 and p300 at target genes. Finally, we demonstrated that Pcgf3/5 are essential for regulating global levels of the histone modifier H2AK119ub1 in ES cells. Our findings establish Pcgf3/5 as transcriptional activators that interact with Tex10 and p300 in ES cells and point to redundant activity of Pcgf3/5 in pluripotency maintenance.

Polycomb/Trithorax Antagonism: Cellular Memory in Stem Cell Fate and Function

“…Recent studies have suggested that PRC1 and PRC2 can be found associated with actively transcribed genes (Cohen et al, 2018;Frangini et al, 2013;Gao et al, 2014;Stojic et al, 2011;van den Boom et al, 2016;Zhao et al, 2017). We note that in many of those cases, PRC1 and PRC2 complexes appear to act as rheostats to help control (reduce) transcriptional output from active genes, thus in fact still mechanistically acting as repressors (Cohen et al, 2018).…”

Polycomb group RING finger protein 5 influences several developmental signaling pathways during the in vitro differentiation of mouse embryonic stem cells

“…Previous reports have shown that Pcgf5 is dispensable for mESC self‐renewal by checking cell morphology and expression of core pluripotency markers (Yao et al, 2018; Zhao et al, 2017). In our study, we also did not detect any major morphological changes between Pcgf5 −/− and WT mESCs grown in 2i/L medium.…”

“…Using different mESC differentiation strategies, two previous studies have reported inconsistent views about whether loss of Pcgf5 results in the maintenance of primed pluripotency and repression of ectodermal generation (Yao et al, 2018; Zhao et al, 2017). Those conflicting results may be due to the distinct cellular contexts of the respective EB models.…”

From Flies to Mice: The Emerging Role of Non-Canonical PRC1 Members in Mammalian Development

“…Not only the similar interaction network, but also the regulated gene sets and distinctive function indicate closer connection between the indicated pairs of complexes. For example, PRC1.3-PRC1.5 mainly function as a transcriptional activator in ES cells, promoting the expression of many genes involved in mesoderm differentiation via interaction of TEX10 transcription factor [180]. Only ncPRC1.6 complex provides link to heterochromatin control system, with its HP1 homolog subunits CBX1 and CBX3.…”

“…In recent studies, it was shown that the association of the complexes with the TEX10 transcription factor plays important role in targeting. TEX10 and p300 connection with ncPRC1.3-ncPRC1.5 necessary for promoting the expression of many genes involved in mesoderm differentiation [180].…”