title: A co-repressor assembly nucleated by Sex-lethal in the 3'UTR mediates translational control of Drosophila msl-2 mRNA.
abstract: Drosophila Sex-lethal (dSXL)-mediated translational repression of male-specific lethal 2 (msl-2) mRNA is essential for X-chromosome dosage compensation. Binding of dSXL to specific sites in both untranslated regions of msl-2 mRNA is necessary for inhibition of translation initiation. We describe the organization of dSXL as a translational regulator and show that the RNA binding and translational repressor functions are contained within the two RRM domains and a C-terminal heptapeptide extension. The repressor function is dormant unless dSXL binds to msl-2 mRNA with its own RRMs, because dSXL tethering via a heterologous RNA-binding peptide does not elicit translational inhibition. We reveal proteins that crosslink to the msl-2 3' untranslated region (3'UTR) and co-immunoprecipitate with dSXL in a fashion that requires its intact repressor domain and correlates with translational regulation. Translation competition and UV-crosslink experiments show that the 3'UTR msl-2 sequences adjacent to dSXL-binding sites are necessary to recruit titratable co-repressors. Our data support a model where dSXL binding to the 3'UTR of msl-2 mRNA activates the translational repressor domain, thereby enabling it to recruit co-repressors in a specific fashion.
authors.affiliation: Gene Expression Programme, European Molecular Biology Laboratory, Meyerhofstrasse 1, 69117 Heidelberg, Germany.
authors.forename: Marica
authors.initials: M
authors.lastname: Grskovic
authors.forename: Matthias W
authors.initials: MW
authors.lastname: Hentze
authors.forename: Fátima
authors.initials: F
authors.lastname: Gebauer
mesh_terms: D020413:3' Untranslated Regions / Q000235:genetics*; D000818:Animals; D003001:Cloning, Molecular; D004268:DNA-Binding Proteins; D004330:Drosophila / Q000235:genetics*; D029721:Drosophila Proteins / Q000235:genetics* / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics; D007301:Insect Hormones / Q000235:genetics / Q000378:metabolism; D008297:Male; D009687:Nuclear Proteins / Q000235:genetics* / Q000378:metabolism*; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000235:genetics*; D016601:RNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012097:Repressor Proteins / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism*; D014158:Transcription, Genetic
chemical_list: D020413:3' Untranslated Regions; D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D007301:Insect Hormones; D009687:Nuclear Proteins; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D011993:Recombinant Fusion Proteins; D012097:Repressor Proteins; C067777:Sxl protein, Drosophila; D014157:Transcription Factors; C094166:msl-2 protein, Drosophila