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<p>The Polycomb group (PcG) protein chromobox 8 (CBX8) is the subunit of Polycomb repressive complex 1 (PRC1) and recognizes the trimethylation of histone H3 on Lysine 27 (H3K27me3), and coordinates with PRC2 complex to function as an epigenetic gene silencer. CBX8 plays a key role in cell proliferation, stem cell biology, cell senescence, and cancer development. However, the post-translational modifications of CBX8 remain poorly understood. Here, we report that protein kinase D1 (PKD1) interacts and phosphorylates CBX8 at Thr234 and Ser256 /311 residues. PKD1-mediated CBX8 phosphorylation at Thr234 reduced its expression level by promoting its ubiquitination-mediated degradation, whereas Ser256/311 phosphorylation decreased CBX8 binding to other PRC1 components BMI1 and RING1A. Overall, CBX8 phosphorylation by PKD1 impaired PRC1 complex integrity and activity, mitigated H2AK119ub1 level, caused the upregulation of multiple target genes repressed by CBX8, and decreased CBX8, H2AK119ub1, and H3K27me3 enrichment at INK4A/ARF locus, thereby derepressing p16<sup>INK4A</sup> and facilitating cellular senescence. Collectively, these results suggest that PKD1-mediated CBX8 phosphorylation at T234 and S256/311 is a key mechanism governing CBX8 function, including cell senescence.</p>

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Phosphorylation of CBX8 by PKD1 suppresses PRC1 activity and promotes cell senescence

  • 期刊论文

  • 发表日期：

    2025年12月15日

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  • Zhiqiang Fang,
  • Doudou Liu,
  • Yuanyuan Su,
  • Fengxin Hao,
  • Ruodong Qin,
  • Guodong Li,
  • Jun Chen

摘要

The Polycomb group (PcG) protein chromobox 8 (CBX8) is the subunit of Polycomb repressive complex 1 (PRC1) and recognizes the trimethylation of histone H3 on Lysine 27 (H3K27me3), and coordinates with PRC2 complex to function as an epigenetic gene silencer. CBX8 plays a key role in cell proliferation, stem cell biology, cell senescence, and cancer development. However, the post-translational modifications of CBX8 remain poorly understood. Here, we report that protein kinase D1 (PKD1) interacts and phosphorylates CBX8 at Thr234 and Ser256 /311 residues. PKD1-mediated CBX8 phosphorylation at Thr234 reduced its expression level by promoting its ubiquitination-mediated degradation, whereas Ser256/311 phosphorylation decreased CBX8 binding to other PRC1 components BMI1 and RING1A. Overall, CBX8 phosphorylation by PKD1 impaired PRC1 complex integrity and activity, mitigated H2AK119ub1 level, caused the upregulation of multiple target genes repressed by CBX8, and decreased CBX8, H2AK119ub1, and H3K27me3 enrichment at INK4A/ARF locus, thereby derepressing p16INK4A and facilitating cellular senescence. Collectively, these results suggest that PKD1-mediated CBX8 phosphorylation at T234 and S256/311 is a key mechanism governing CBX8 function, including cell senescence.