Cross-talk among writers, readers, and erasers of m ⁶ A regulates cancer growth and progression

Abstract

The importance of RNA methylation in biological processes is an emerging focus of investigation. We report that altering m⁶A levels by silencing either <i>N</i> ⁶-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 m⁶A 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 m⁶A modifications, as altered m⁶A 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 m⁶A status of target genes by controlling each other's expression and by inhibiting m⁶A reader YTHDF3 (YTH <i>N</i> ⁶-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 m⁶A and consequently increased expression of target transcripts in cancer cells. This study unveils a previously undefined role for m⁶A in cancer and shows that the collaboration among writers-erasers-readers sets up the m⁶A threshold to ensure the stability of progrowth/proliferation-specific genes, and protumorigenic stimulus, such as hypoxia, perturbs that m⁶A threshold, leading to uncontrolled expression/activity of those genes, resulting in tumor growth, angiogenesis, and progression.