Ring1, also known as ring finger protein 1, is an E3 ubiquitin-protein ligase. It is a core component of the Polycomb repressive complex 1 (PRC1), which modifies chromatin through catalyzing histone H2A lysine 119 monoubiquitination (H2AK119ub1). Ring1 is involved in various biological processes such as development, cell cycle regulation, and is associated with pathways like Wnt/β-catenin, Notch, and DNA damage repair pathways [1,3,6]. It plays a vital role in carcinogenesis, stem cell self-renewal, and plant defense mechanisms [1,2,3,4]. Genetic models, especially knockout models, are valuable for studying Ring1's functions.

In a mouse model, depletion of RING1 proteins (RING1A and RING1B) led to severe forelimb formation defects along the proximal-distal axis, suggesting its role in early forelimb bud patterning by restricting Meis2 expression [5]. In an in vitro neurodevelopment model, hypomorphic RING1 in PRC1 complexes reduced H2AK119ub1, causing delayed DNA damage repair and cell cycle progression in neural progenitor cells, highlighting its importance in neurogenesis [1]. In hepatic progenitor cells, overexpression of Ring1 promoted their transformation into cancer stem-like cells via the Wnt/β-catenin signaling pathway [3]. In tomato plants, ring1 mutants showed increased susceptibility to root-knot nematodes, indicating its positive role in plant defense [4].

In conclusion, Ring1 is crucial for multiple biological functions including development, neurogenesis, carcinogenesis, and plant defense. Knockout models in mice and other organisms have significantly contributed to understanding its role in these processes. These findings have implications for diseases related to abnormal development, neural disorders, and cancer [1,3,4,5].