Disruption of PRC1 components RING1A and RING1B promotes angiogenesis via relieving BMP4 repression.

INTRODUCTION: Angiogenesis is crucial for tissue homeostasis and vascular regeneration following ischemia or injury. Epigenetic regulation has emerged as a key determinant of angiogenic gene expression. The Polycomb repressive complex 1 (PRC1) is a major epigenetic regulator that mediates gene silencing through monoubiquitylation of histone H2A at lysine 119 (H2AK119ub), a process primarily catalyzed by its core components RING1A and RING1B. However, the role of RING1A and RING1B in angiogenesis remains unclear. OBJECTIVES: In this study, we aimed to investigate the function and underlying mechanism of RING1A and RING1B in regulating endothelial cell functions and angiogenesis. METHODS: We performed loss-of-function experiments using siRNAs targeting RING1A and RING1B in vitro and in vivo. Endothelial function was evaluated by tube formation, acetylated low-density lipoprotein (ac-LDL) uptake, nitric oxide production, proliferation, and migration. To identify downstream targets, we integrated RNA sequencing data from RING1A or RING1B knockdown endothelial cells with Cleavage Under Targets and Tagmentation profiling of RING1A, RING1B, and H2AK119ub. In vivo angiogenesis was examined using a Matrigel plug model and a corneal alkali-burn injury model in mice. RESULTS: Knockdown of RING1A and RING1B significantly promoted tube formation, ac-LDL uptake, and nitric oxide production. Notably, only RING1A knockdown impaired endothelial proliferation and migration. Both RING1A and RING1B knockdown drastically promoted angiogenesis in vivo. Integrative analysis identified BMP4 as a direct transcriptional target of PRC1-mediated repression during angiogenesis. CONCLUSION: Our findings indicate that RING1A and RING1B play a repressive role in angiogenesis by epigenetically silencing BMP4 gene expression through H2AK119ub. Targeting PRC1-mediated repression may represent a novel therapeutic approach to promote angiogenesis in ischemic diseases.