Hrp48 and eIF3d contribute to msl-2 mRNA translational repression

Szóstak, Emilia, 1984-; García Beyaert, Marina, 1983-; Guitart, Tanit; Graindorge, Antoine; Coll, Olga; Gebauer, Fátima

doi:http://dx.doi.org/10.1093/nar/gky246

Hrp48 and eIF3d contribute to msl-2 mRNA translational repression

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Szostak E, García-Beyaert M, Guitart T, Graindorge A, Coll O, Gebauer F. Hrp48 and eIF3d contribute to msl-2 mRNA translational repression. Nucleic Acids Res. 2018;46(8):4099-113. DOI: 10.1093/nar/gky246

Abstract

Translational repression of msl-2 mRNA in females of Drosophila melanogaster is an essential step in the regulation of X-chromosome dosage compensation. Repression is orchestrated by Sex-lethal (SXL), which binds to both untranslated regions (UTRs) of msl-2 and inhibits translation initiation by poorly understood mechanisms. Here we identify Hrp48 as a SXL co-factor. Hrp48 binds to the 3' UTR of msl-2 and is required for optimal repression by SXL. Hrp48 interacts with eIF3d, a subunit of the eIF3 translation initiation complex. Reporter and RNA chromatography assays showed that eIF3d binds to msl-2 5' UTR, and is required for efficient translation and translational repression of msl-2 mRNA. In line with these results, eIF3d depletion -but not depletion of other eIF3 subunits- de-represses msl-2 expression in female flies. These data are consistent with a model where Hrp48 inhibits msl-2 translation by targeting eIF3d. Our results uncover an important step in the mechanism of msl-2 translation regulation, and illustrate how general translation initiation factors can be co-opted by RNA binding proteins to achieve mRNA-specific control.