Qi L1,2, Song Y1, Chan THM1, Yang H1, Lin CH3, Tay DJT1, Hong H1, Tang SJ1, Tan KT1, Huang XX1, Lin JS1, Ng VHE1, Maury JJP4, Tenen DG1,5, Chen L1,6.
1 Cancer Science Institute of Singapore, National University of Singapore, Singapore.
2 Duke-NUS Medical School, National University of Singapore, Singapore.
3 Centre for Genomic Sciences, the University of Hong Kong, Hong Kong.
4 Institute of Molecular and Cell Biology, A*STAR, Singapore.
5 Harvard Stem Cell Institute, Harvard Medical School, Boston, MA, USA.
6 Department of Anatomy, National University of Singapore, Singapore.
Adenosine-to-inosine (A-to-I) RNA editing, catalyzed by Adenosine DeAminases acting on double-stranded RNA(dsRNA) (ADAR), occurs predominantly in the 3′ untranslated regions (3’UTRs) of spliced mRNA. Here we uncover an unanticipated link between ADARs (ADAR1 and ADAR2) and the expression of target genes undergoing extensive 3’UTR editing. Using METTL7A (Methyltransferase Like 7A), a novel tumor suppressor gene with multiple editing sites at its 3’UTR, we demonstrate that its expression could be repressed by ADARs beyond their RNA editing and double-stranded RNA (dsRNA) binding functions. ADARs interact with Dicer to augment the processing of pre-miR-27a to mature miR-27a. Consequently, mature miR-27a targets the METTL7A 3’UTR to repress its expression level. In sum, our study unveils that the extensive 3’UTR editing of METTL7A is merely a footprint of ADAR binding, and there are a subset of target genes that are equivalently regulated by ADAR1 and ADAR2 through their non-canonical RNA editing and dsRNA binding-independent functions, albeit maybe less common. The functional significance of ADARs is much more diverse than previously appreciated and this gene regulatory function of ADARs is most likely to be of high biological importance beyond the best-studied editing function. This non-editing side of ADARs opens another door to target cancer.