The <i>Drosophila</i> Nab2 RNA binding protein inhibits m⁶A methylation and male-specific splicing of <i>Sex lethal</i> transcript in female neuronal tissue.

Abstract

The <i>Drosophila</i> polyadenosine RNA binding protein Nab2, which is orthologous to a human protein lost in a form of inherited intellectual disability, controls adult locomotion, axon projection, dendritic arborization, and memory through a largely undefined set of target RNAs. Here, we show a specific role for Nab2 in regulating splicing of ~150 exons/introns in the head transcriptome and focus on retention of a male-specific exon in the sex determination factor <i>Sex-lethal</i> (<i>Sxl</i>) that is enriched in female neurons. Previous studies have revealed that this splicing event is regulated in females by N6-methyladenosine (m⁶A) modification by the Mettl3 complex. At a molecular level, Nab2 associates with <i>Sxl</i> pre-mRNA in neurons and limits <i>Sxl</i> m⁶A methylation at specific sites. In parallel, reducing expression of the Mettl3, Mettl3 complex components, or the m⁶A reader Ythdc1 rescues mutant phenotypes in <i>Nab2</i> flies. Overall, these data identify Nab2 as an inhibitor of m⁶A methylation and imply significant overlap between Nab2 and Mettl3 regulated RNAs in neuronal tissue.