The mA-methylase complex recruits TREX and regulates mRNA export.

N-methyladenosine (mA) is the most abundant internal modification of eukaryotic mRNA. This modification has previously been shown to alter the export kinetics for mRNAs though the molecular details surrounding this phenomenon remain poorly understood. Recruitment of the TREX mRNA export complex to mRNA is driven by transcription, 5' capping and pre-mRNA splicing. Here we identify a fourth mechanism in human cells driving the association of TREX with mRNA involving the mA methylase complex. We show that the mA complex recruits TREX to mA modified mRNAs and this process is essential for their efficient export. TREX also stimulates recruitment of the mA reader protein YTHDC1 to the mRNA and the mA complex influences the interaction of TREX with YTHDC1. Together our studies reveal a key role for TREX in the export of mA modified mRNAs.