LINC00955 通过作为 TRIM25 和 Sp1 的分子支架来抑制 DNMT3B 介导的 PHIP 启动子甲基化，从而抑制结直肠癌细胞生长。

BACKGROUND: Long non-coding RNAs play an important role in the development of colorectal cancer (CRC), while many CRC-related lncRNAs have not yet been identified. METHODS: The relationship between the expression of LINC00955 (Long Intergenic Non-protein Coding RNA 955) and the prognosis of colorectal cancer patients was analyzed using the sequencing results of the TCGA database. LINC00955 expression levels were measured using qRT-PCR. The anti-proliferative activity of LINC00955 was evaluated using CRC cell lines in vitro and xenograft models in nude mice in vivo. The interaction of TRIM25-Sp1-DNMT3B-PHIP-CDK2 was analyzed by western blotting, protein degradation experiment, luciferase, RNA-IP, RNA pull-down assays and immunohistochemically analysis. The biological roles of LINC00955, tripartite motif containing 25 (TRIM25), Sp1 transcription factor (Sp1), DNA methyltransferase 3 beta (DNMT3B), pleckstrin homology domain interacting protein (PHIP), cyclin dependent kinase 2 (CDK2) in colorectal cancer cells were analyzed using ATP assays, Soft agar experiments and EdU assays. RESULTS: The present study showed that LINC00955 is downregulated in CRC tissues, and such downregulation is associated with poor prognosis of CRC patients. We found that LINC00955 can inhibit CRC cell growth both in vitro and in vivo. Evaluation of its mechanism of action showed that LINC00955 acts as a scaffold molecule that directly promotes the binding of TRIM25 to Sp1, and promotes ubiquitination and degradation of Sp1, thereby attenuating transcription and expression of DNMT3B. DNMT3B inhibition results in hypomethylation of the PHIP promoter, in turn increasing PHIP transcription and promoting ubiquitination and degradation of CDK2, ultimately leading to G0/G1 growth arrest and inhibition of CRC cell growth. CONCLUSIONS: These findings indicate that downregulation of LINC00955 in CRC cells promotes tumor growth through the TRIM25/Sp1/DNMT3B/PHIP/CDK2 regulatory axis, suggesting that LINC00955 may be a potential target for the therapy of CRC.

背景：长非编码 RNA 在结直肠癌（CRC）的发展中发挥重要作用，而许多与 CRC 相关的 lncRNA 尚未被确定。

方法：使用 TCGA 数据库的测序结果分析 LINC00955（长基因间非蛋白编码 RNA 955）的表达与结直肠癌患者预后的关系。使用 qRT-PCR 测量 LINC00955 的表达水平。在体外使用 CRC 细胞系和体内裸鼠移植瘤模型评估 LINC00955 的抗增殖活性。通过 Western blot、蛋白降解实验、荧光素酶报告基因、RNA-IP、RNA 下拉实验和免疫组织化学分析分析 TRIM25-Sp1-DNMT3B-PHIP-CDK2 的相互作用。使用 ATP 测定、软琼脂实验和 EdU 测定分析 LINC00955、三肽重复含 25 个氨基酸（TRIM25）、Sp1 转录因子（Sp1）、DNA 甲基转移酶 3β（DNMT3B）、pleckstrin 同源结构域相互作用蛋白（PHIP）、细胞周期蛋白依赖性激酶 2（CDK2）在结直肠癌细胞中的生物学作用。

结果：本研究表明 LINC00955 在 CRC 组织中下调，这种下调与 CRC 患者的不良预后相关。我们发现 LINC00955 可以在体外和体内抑制 CRC 细胞的生长。对其作用机制的评估表明，LINC00955 作为一种支架分子，直接促进 TRIM25 与 Sp1 的结合，并促进 Sp1 的泛素化和降解，从而减弱 DNMT3B 的转录和表达。DNMT3B 抑制导致 PHIP 启动子的低甲基化，进而增加 PHIP 转录并促进 CDK2 的泛素化和降解，最终导致 G0/G1 生长停滞并抑制 CRC 细胞生长。

结论：这些发现表明 CRC 细胞中 LINC00955 的下调通过 TRIM25/Sp1/DNMT3B/PHIP/CDK2 调节轴促进肿瘤生长，表明 LINC00955 可能是 CRC 治疗的潜在靶点。