Department of Cell Systems and Anatomy, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229, USA.
Greehey Children's Cancer Research Institute, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229, USA.
Sci Adv. 2018 Oct 3;4(10):eaar8263. doi: 10.1126/sciadv.aar8263. eCollection 2018 Oct.
The importance of RNA methylation in biological processes is an emerging focus of investigation. We report that altering mA levels by silencing either -adenosine methyltransferase METTL14 (methyltransferase-like 14) or demethylase ALKBH5 (ALKB homolog 5) inhibits cancer growth and invasion. METTL14/ALKBH5 mediate their protumorigenic function by regulating mA levels of key epithelial-mesenchymal transition and angiogenesis-associated transcripts, including transforming growth factor-β signaling pathway genes. Using MeRIP-seq (methylated RNA immunoprecipitation sequencing) analysis and functional studies, we find that these target genes are particularly sensitive to changes in mA modifications, as altered mA status leads to aberrant expression of these genes, resulting in inappropriate cell cycle progression and evasion of apoptosis. Our results reveal that METTL14 and ALKBH5 determine the mA status of target genes by controlling each other's expression and by inhibiting mA reader YTHDF3 (YTH -methyladenosine RNA binding protein 3), which blocks RNA demethylase activity. Furthermore, we show that ALKBH5/METTL14 constitute a positive feedback loop with RNA stability factor HuR to regulate the stability of target transcripts. We discover that hypoxia alters the level/activity of writers, erasers, and readers, leading to decreased mA and consequently increased expression of target transcripts in cancer cells. This study unveils a previously undefined role for mA in cancer and shows that the collaboration among writers-erasers-readers sets up the mA threshold to ensure the stability of progrowth/proliferation-specific genes, and protumorigenic stimulus, such as hypoxia, perturbs that mA threshold, leading to uncontrolled expression/activity of those genes, resulting in tumor growth, angiogenesis, and progression.
RNA 甲基化在生物过程中的重要性是一个新的研究焦点。我们报告称，沉默腺苷甲基转移酶 METTL14（甲基转移酶样 14）或去甲基酶 ALKBH5（ALKB 同源物 5）均可改变 mA 水平，从而抑制癌症的生长和侵袭。METTL14/ALKBH5 通过调节关键上皮-间充质转化和血管生成相关转录物的 mA 水平，发挥其促肿瘤功能，包括转化生长因子-β信号通路基因。通过 MeRIP-seq（甲基化 RNA 免疫沉淀测序）分析和功能研究，我们发现这些靶基因对 mA 修饰的变化特别敏感，因为改变的 mA 状态导致这些基因的异常表达，从而导致细胞周期进程不当和逃避细胞凋亡。我们的结果表明，METTL14 和 ALKBH5 通过相互控制表达和抑制 mA 阅读器 YTHDF3（YTH-甲基腺苷 RNA 结合蛋白 3）来决定靶基因的 mA 状态，YTHDF3 会阻止 RNA 去甲基酶的活性。此外，我们还表明，ALKBH5/METTL14 与 RNA 稳定性因子 HuR 构成正反馈回路，以调节靶转录本的稳定性。我们发现缺氧会改变书写器、橡皮擦和阅读器的水平/活性，导致 mA 减少，从而导致癌细胞中靶转录本的表达增加。这项研究揭示了 mA 在癌症中的一个以前未定义的作用，并表明书写器-橡皮擦-阅读器之间的协作设定了 mA 阈值，以确保与生长/增殖相关基因的稳定性，而缺氧等促肿瘤刺激会破坏该 mA 阈值，导致这些基因的不受控制的表达/活性，从而导致肿瘤生长、血管生成和进展。
