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

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