N 6 -Methyladenosine landscape of glioma stem-like cells: METTL3 is essential for the expression of actively transcribed genes and sustenance of the oncogenic signaling

Despite recent advances in N 6 -methyladenosine (m 6 A) biology, the regulation of crucial RNA processing steps by the RNA methyltransferase-like 3 (METTL3) in glioma stem-like cells (GSCs) remains obscure. An integrated analysis of m 6 A-RIP (RNA immunoprecipitation) and total RNA-Seq of METTL3-silenced GSCs identified that m 6 A modification in GSCs is principally carried out by METTL3. The m 6 A-modified transcripts showed higher abundance compared to non-modified transcripts. Further, we showed that the METTL3 is essential for the expression of GSC-specific actively transcribed genes. Silencing METTL3 resulted in the elevation of several aberrant alternative splicing events. We also found that putative m 6 A reader proteins play a key role in the RNA stabilization function of METTL3. METTL3 altered A-to-I and C-to-U RNA editing events by differentially regulating RNA editing enzymes ADAR and APOBEC3A. Similar to protein-coding genes, lincRNAs (long intergenic non-coding RNAs) with m 6 A marks showed METTL3-dependent high expression. m 6 A modification of 30UTRs appeared to result in a conformation-dependent hindrance to miRNA binding to their targets. The integrated analysis of the m 6 A regulome in METTL3-silenced GSCs showed global disruption in tumorigenic pathways that are indispensable for GSC maintenance and glioma progression. We conclude that METTL3 plays a vital role in many steps of RNA processing and orchestrates successful execution of oncogenic pathways in GSCs. © 2019 by the authors. Licensee MDPI, Basel, Switzerland