Xio is a component of the Drosophila sex determination pathway and RNA N 6 -methyladenosine methyltransferase complex

Significance RNAs contain over 100 types of chemical modifications, and N 6 -methyladenosine (m 6 A) is the most common internal modification in eukaryotic mRNA. m 6 A is involved in a variety of important biological processes, including sex determination in Drosophila , by modifying Sxl pre-mRNA and regulating its alternative splicing. m 6 A is installed by a large methyltransferase complex called the m 6 A “writer.” We have identified xio as a component of the Drosophila sex determination pathway based on its female-to-male transformation phenotypes. Xio interacts with other m 6 A writer subunits, and its loss of function shows typical phenotypes associated with other m 6 A factors, such as Sxl splicing misregulation, adult defects, and reduced m 6 A levels. Therefore, we conclude that Xio is a member of the m 6 A writer complex.