Update publication information. Molecular mechanisms of HIV-1 latency have been studied extensively to achieve a functional cure for the acquired immunodeficiency syndrome (AIDS). To develop more promising latency-reversing agents (LRAs) to efficiently reactivate the latent reservoir which is subsequently eliminated by immune surveillance, new therapeutic targets need to be evaluated. Here, we found that the Polycomb group (PcG) protein CBX4 contributes to HIV-1 latency in many latency models and primary CD4+ T cells. CBX4 forms nuclear bodies with liquid–liquid phase separation (LLPS) properties on the HIV-1 long terminal repeat (LTR). Further proteomics analysis revealed that CBX4 recruits EZH2 to CBX4 bodies and SUMOylates EZH2 utilizing its SUMO E3 ligase activity, which enhances the H3K27 methyltransferase activity of EZH2. Our results indicated that CBX4 bridges the Polycomb repressive complex 1 (PRC1) and PRC2, resulting in synergistically maintaining HIV-1 latency. Dissolution of phase-separated CBX4 bodies could be a potential intervention to reactivate latent HIV-1.