Maintenance of Nucleolar
Homeostasis by CBX4 Alleviates Senescence and Osteoarthritis.
Abstract
CBX4, a component of polycomb repressive complex
1 (PRC1), plays important roles in the maintenance of cell identity and organ
development through gene silencing. However, whether CBX4 regulates human stem
cell homeostasis remains unclear. Here, we demonstrate that CBX4 counteracts
human mesenchymal stem cell (hMSC) aging via the maintenance of nucleolar
homeostasis. CBX4 protein is downregulated in aged hMSCs, whereas CBX4 knockout
in hMSCs results in destabilized nucleolar heterochromatin, enhanced ribosome
biogenesis, increased protein translation, and accelerated cellular senescence.
CBX4 maintains nucleolar homeostasis by recruiting nucleolar protein
fibrillarin (FBL) and heterochromatin protein KRAB-associated protein 1 (KAP1)
at nucleolar rDNA, limiting the excessive expression of rRNAs. Overexpression
of CBX4 alleviates physiological hMSC aging and attenuates the development of
osteoarthritis in mice. Altogether, our findings reveal a critical role of
CBX4 in counteracting cellular senescence by maintaining nucleolar homeostasis,
providing a potential therapeutic target for aging-associated disorders.
https://www.blogger.com/blogger.g?blogID=7133329557719394967#editor/target=post;postID=3309817050533485115
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