Abstract

N6-methyladenosine (m 6 A), the most abundant internal modification in eukaryotic mRNA, is installed by a multi-component writer complex; however, the exact roles of each component remain poorly understood. Here we show that a potential E3 ubiquitin ligase Hakai colocalizes and interacts with other m 6 A writer components, and Hakai mutants exhibit typical m 6 A pathway defects in Drosophila , such as lowered m 6 A levels in mRNA, aberrant Sxl alternative splicing, wing and behavior defects. Hakai, Vir, Fl(2)d and Flacc form a stable complex, and disruption of either Hakai, Vir or Fl(2)d led to the degradation of the other three components. Furthermore, MeRIP-seq indicates that the effective m 6 A modification is mostly distributed in 5’ UTRs in Drosophila , in contrast to the mammalian system. Interestingly, we demonstrate that m 6 A modification is deposited onto the Sxl mRNA in a sex-specific fashion, which depends on the m 6 A writer. Together, our work not only advances the understanding of mechanism and regulation of the m 6 A writer complex, but also provides insights into how Sxl cooperate with the m 6 A pathway to control its own splicing.