Department of Biomedical Engineering, Indian Institute of Technology Ropar, Rupnagar, Punjab, India.
J Transl Med. 2024 Oct 5;22(1):904. doi: 10.1186/s12967-024-05715-5.
Hyperactive RNA Polymerase I (Pol I) transcription is canonical in cancer, associated with malignant proliferation, poor prognosis, epithelial-mesenchymal transition, and chemotherapy resistance. Despite its significance, the molecular mechanisms underlying Pol I hyperactivity remain unclear. This study aims to elucidate the role of long noncoding RNAs (lncRNAs) in regulating Pol I transcription in lung adenocarcinoma (LUAD).
Bioinformatics analyses were applied to identify lncRNAs interacting with Pol I transcriptional machinery. Fluorescence in situ hybridization was employed to examine the nucleolar localization of candidate lncRNA in LUAD cells. RNA immunoprecipitation assay validated the interaction between candidate lncRNA and Pol I components. Chromatin isolation by RNA purification and Chromatin Immunoprecipitation (ChIP) were utilized to confirm the interactions of candidate lncRNA with Pol I transcriptional machinery and the rDNA core promoter. Functional analyses, including lncRNA knock-in and knockdown, inhibition of Pol I transcription, quantitative PCR, cell proliferation, clonogenicity, apoptosis, cell cycle, wound-healing, and invasion assays, were performed to determine the effect of candidate lncRNA on Pol I transcription and associated malignant phenotypes in LUAD cells. ChIP assays and luminometry were used to investigate the transcriptional regulation of the candidate lncRNA.
We demonstrate that oncogenic LINC01116 scaffolds essential Pol I transcription factors TAF1A and TAF1D, to the ribosomal DNA promoter, and upregulate Pol I transcription. Crucially, LINC01116-driven Pol I transcription activation is essential for its oncogenic activities. Inhibition of Pol I transcription abrogated LINC01116-induced oncogenic phenotypes, including increased proliferation, cell cycle progression, clonogenicity, reduced apoptosis, increased migration and invasion, and drug sensitivity. Conversely, LINC01116 knockdown reversed these effects. Additionally, we show that LINC01116 upregulation in LUAD is driven by the oncogene c-Myc, a known Pol I transcription activator, indicating a functional regulatory feedback loop within the c-Myc-LINC01116-Pol I transcription axis.
Collectively, our findings reveal, for the first time, that LINC01116 enhances Pol I transcription by scaffolding essential transcription factors to the ribosomal DNA promoter, thereby driving oncogenic activities in LUAD. We propose the c-Myc-LINC01116-Pol I axis as a critical oncogenic pathway and a potential therapeutic target for modulating Pol I transcription in LUAD.
高度活跃的 RNA 聚合酶 I（Pol I）转录在癌症中是典型的，与恶性增殖、预后不良、上皮-间充质转化和化疗耐药有关。尽管其意义重大，但 Pol I 过度活跃的分子机制仍不清楚。本研究旨在阐明长非编码 RNA（lncRNA）在调节肺腺癌（LUAD）中 Pol I 转录中的作用。
应用生物信息学分析鉴定与 Pol I 转录机制相互作用的 lncRNA。应用荧光原位杂交检测候选 lncRNA 在 LUAD 细胞中的核仁定位。RNA 免疫沉淀测定验证候选 lncRNA 与 Pol I 成分的相互作用。通过 RNA 纯化和染色质免疫沉淀（ChIP）分离染色质，证实候选 lncRNA 与 Pol I 转录机制和 rDNA 核心启动子的相互作用。进行 lncRNA 敲入和敲低、Pol I 转录抑制、定量 PCR、细胞增殖、集落形成、细胞凋亡、细胞周期、划痕愈合和侵袭测定等功能分析，以确定候选 lncRNA 对 LUAD 细胞中 Pol I 转录和相关恶性表型的影响。ChIP 测定和发光测定用于研究候选 lncRNA 的转录调节。
我们证明致癌的 LINC01116 支架必需的 Pol I 转录因子 TAF1A 和 TAF1D 到核糖体 DNA 启动子，并上调 Pol I 转录。至关重要的是，LINC01116 驱动的 Pol I 转录激活对于其致癌活性是必需的。Pol I 转录抑制消除了 LINC01116 诱导的致癌表型，包括增殖增加、细胞周期进程加快、集落形成能力增强、凋亡减少、迁移和侵袭增加以及药物敏感性降低。相反，LINC01116 的敲低逆转了这些效应。此外，我们表明，LUAD 中 LINC01116 的上调是由癌基因 c-Myc 驱动的，c-Myc 是一种已知的 Pol I 转录激活剂，表明 c-Myc-LINC01116-Pol I 转录轴内存在功能调节反馈环。
总的来说，我们的研究结果首次揭示，LINC01116 通过将必需的转录因子支架到核糖体 DNA 启动子上来增强 Pol I 转录，从而在 LUAD 中驱动致癌活性。我们提出 c-Myc-LINC01116-Pol I 轴作为一个关键的致癌途径，并作为调节 LUAD 中 Pol I 转录的潜在治疗靶点。
