低氧是实体肿瘤的标志，导致癌细胞的代谢重组。低氧与结直肠癌(CRC)中异常胆固醇代谢的表观遗传调控作用仍不清楚。通过高通量RNA测序在正氧和低氧下培养的CRC细胞之间鉴定低氧响应的环状RNA(circRNA)。通过多聚体分析和液相色谱-质谱法确定了circINSIG1的蛋白编码潜力。通过增加或减少circINSIG1的功能实验在体内和体外验证了其功能。通过免疫沉淀分析得出了机械结果。鉴定了一个新的低氧响应circRNA，名为circINSIG1，它在CRC组织中上调，与晚期临床分期和不良生存率相关。在机械上，circINSIG1编码一个121个氨基酸的蛋白质circINSIG1-121，通过招募泛素E3连接酶CUL5-ASB6复合体来促进临界胆固醇代谢调节器INSIG1的K48-连接泛素化，从而诱导胆固醇合成以促进CRC增殖和转移。原位移植瘤模型和患者来源的移植瘤模型进一步确认了circINSIG1在CRC进展中的作用，并成为CRC的潜在治疗靶点。circINSIG1提出了一种表观遗传机制，揭示了低氧和胆固醇代谢之间的相互作用，并为CRC的治疗提供了有希望的治疗靶点。©2023. 作者。

Hypoxia is a hallmark of solid tumors and leads to the metabolic reprogramming of cancer cells. The role of epigenetic regulation between hypoxia and aberrant cholesterol metabolism in colorectal cancer (CRC) remains elusive.Hypoxia-responsive circular RNAs (circRNAs) were identified by high throughput RNA sequencing between CRC cells cultured under normoxia or hypoxia. The protein-coding potential of circINSIG1 was identified by polysome profiling and LC-MS. The function of circINSIG1 was validated in vitro and in vivo by gain or loss of function assays. Mechanistic results were concluded by immunoprecipitation analyses.A novel hypoxia-responsive circRNA named circINSIG1 was identified, which was upregulated in CRC tissues and correlated with advanced clinical stages and poor survival. Mechanistically, circINSIG1 encoded a 121 amino acid protein circINSIG1-121 to promote K48-linked ubiquitination of the critical cholesterol metabolism regulator INSIG1 at lysine 156 and 158 by recruiting CUL5-ASB6 complex, a ubiquitin E3 ligase complex, thereby inducing cholesterol biosynthesis to promote CRC proliferation and metastasis. The orthotopic xenograft tumor models and patient-derived xenograft models further identified the role of circINSIG1 in CRC progression and potential therapeutic target of CRC.circINSIG1 presents an epigenetic mechanism which provides insights into the crosstalk between hypoxia and cholesterol metabolism, and provides a promising therapeutic target for the treatment of CRC.© 2023. The Author(s).