Abstract
Brpf-histone acetyltransferase (HAT) complexes have important roles in embryonic development and regulating differentiation in ESCs. Among Brpf family, Brpf3 is a scaffold protein of Myst2 histone acetyltransferase complex that plays crucial roles in gene regulation, DNA replication, development as well as maintaining pluripotency in embryonic stem cells (ESCs). However, its biological functions in ESCs are not elucidated. In this study, we find out that Brpf3 protein level is critical for Myst2 stability and E3 ligase Huwe1 functions as a novel negative regulator of Myst2 via ubiquitin-mediated degradation. Importantly, Brpf3 plays an antagonistic role in Huwe1-mediated degradation of Myst2, suggesting that protein–protein interaction between Brpf3 and Myst2 is required for retaining Myst2 stability. Further, Brpf3 overexpression causes the aberrant upregulation of Myst2 protein levels which in turn induces the dysregulated cell-cycle progression and also delay of early embryonic development processes such as embryoid-body formation and lineage commitment of mouse ESCs. The Brpf3 overexpression-induced phenotypes can be reverted by Huwe1 overexpression. Together, these results may provide novel insights into understanding the functions of Brpf3 in proper differentiation as well as cell-cycle progression of ESCs via regulation of Myst2 stability by obstructing Huwe1-mediated ubiquitination. In addition, we suggest that this is a useful report which sheds light on the function of an unknown gene in ESC field.
Highlights
These authors contributed : Hye In Cho, Min Seong KimEdited by G
Our findings demonstrate for the first time that Brpf3 regulates protein stability of Myst2 by inhibiting Huwe1-mediated degradation and that it is required for differentiation and cell-cycle progression in mouse ESCs (mESCs)
We investigated whether Brpf3 deficiency affects Myst2 expression using western blot and RNA isolation and quantitative reverse transcription PCR (RT-qPCR) analyses in both shRNA-based knockdown (KD) cell lines and Brpf3 haploinsufficient mESCs created by CRISPR-CAS9 (Supplementary Fig. S1b, c)
Summary
The Brpf2/ MOZ complex is required for differentiation induced by retinoic acid in mouse ESCs (mESCs) [6]. Huwe ubiquitinates N-Myc and the knockout of Huwe induces impairment of neuronal differentiation in ESCs. protein expression of Huwe increases during differentiation [10], implying that Huwe is involved in differentiation. Regulation of pluripotency-related factor such as Myst by Huwe has not been reported yet. We investigated the function of Brpf in mESCs. Our data showed that Brpf regulates protein stability of Myst by protein–protein interaction. Our findings demonstrate for the first time that Brpf regulates protein stability of Myst by inhibiting Huwe1-mediated degradation and that it is required for differentiation and cell-cycle progression in mESCs
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