Department of Biochemistry and Molecular Biology, University of Florida, Gainesville, FL 32610, USA; UF Health Cancer Center, University of Florida, Gainesville, FL 32610, USA.
Department of Molecular Genetics & Microbiology, University of Florida, Gainesville, FL 32610, USA; UF Genetics Institute, University of Florida, Gainesville, FL 32610, USA.
Mol Cell. 2023 Nov 2;83(21):3818-3834.e7. doi: 10.1016/j.molcel.2023.09.020. Epub 2023 Oct 10.
N-methyladenosine (mA) modifications play crucial roles in RNA metabolism. How mA regulates RNA polymerase II (RNA Pol II) transcription remains unclear. We find that 7SK small nuclear RNA (snRNA), a regulator of RNA Pol II promoter-proximal pausing, is highly mA-modified in non-small cell lung cancer (NSCLC) cells. In A549 cells, we identified eight mA sites on 7SK and discovered methyltransferase-like 3 (METTL3) and alkB homolog 5 (ALKBH5) as the responsible writer and eraser. When the mA-7SK is specifically erased by a dCasRx-ALKBH5 fusion protein, A549 cell growth is attenuated due to reduction of RNA Pol II transcription. Mechanistically, removal of mA leads to 7SK structural rearrangements that facilitate sequestration of the positive transcription elongation factor b (P-TEFb) complex, which results in reduction of serine 2 phosphorylation (Ser2P) in the RNA Pol II C-terminal domain and accumulation of RNA Pol II in the promoter-proximal region. Taken together, we uncover that mA modifications of a non-coding RNA regulate RNA Pol II transcription and NSCLC tumorigenesis.
N6-甲基腺苷（m6A）修饰在 RNA 代谢中发挥着关键作用。m6A 如何调节 RNA 聚合酶 II（RNA Pol II）转录尚不清楚。我们发现，7SK 小核 RNA（snRNA）是 RNA Pol II 启动子近端暂停的调节剂，在非小细胞肺癌（NSCLC）细胞中高度 m6A 修饰。在 A549 细胞中，我们在 7SK 上鉴定了八个 m6A 位点，并发现甲基转移酶样 3（METTL3）和 alkB 同源物 5（ALKBH5）是负责写入和擦除的酶。当 mA-7SK 被 dCasRx-ALKBH5 融合蛋白特异性擦除时，由于 RNA Pol II 转录减少，A549 细胞生长受到抑制。在机制上，m6A 的去除导致 7SK 结构重排，从而促进正转录延伸因子 b（P-TEFb）复合物的隔离，导致 RNA Pol II C 末端结构域丝氨酸 2 磷酸化（Ser2P）减少和 RNA Pol II 在启动子近端区域积累。总之，我们揭示了非编码 RNA 的 m6A 修饰调节 RNA Pol II 转录和 NSCLC 肿瘤发生。
