Structure and novel functional mechanism of Drosophila SNF in sex-lethal splicing

• Published in: PloS one 2009-09, Vol.4 (9), p.e6890-e6890
• Main Authors: Hu, Jicheng, Cui, Gaofeng, Li, Congmin, Liu, Cong, Shang, Erchang, Lai, Luhua, Jin, Changwen, Wang, Jiwu, Xia, Bin
• Format: Article
• Language: English
• Subjects: Alternative Splicing; Animals; Automation; Binding; Biochemistry/Biomacromolecule-Ligand Interactions; Biophysics/Biomacromolecule-Ligand Interactions; Chemistry; Drosophila; Drosophila melanogaster - genetics; Drosophila melanogaster - metabolism; Engineering; Exon skipping; Exons; Female; Females; Homology; Insects; Introns; Life sciences; Magnetic Resonance Spectroscopy; Male; Males; Messenger RNA; Models, Genetic; Molecular Biology/RNA Splicing; Molecular Biology/RNA-Protein Interactions; Molecular Conformation; mRNA; Mutation; Next-generation sequencing; NMR; Nuclear magnetic resonance; Nucleotide sequence; Protein Binding; Proteins; Ribonucleic acid; Ribonucleoproteins (small nuclear); RNA; RNA - chemistry; RNA - metabolism; RNA Splicing; RNA-Binding Proteins - metabolism; Sex; Sex determination; Sex Determination Processes; snRNA; Splicing factors; Uridine - metabolism
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0006890

Sans-fille (SNF) is the Drosophila homologue of mammalian general splicing factors U1A and U2B'', and it is essential in Drosophila sex determination. We found that, besides its ability to bind U1 snRNA, SNF can also bind polyuridine RNA tracts flanking the male-specific exon of the master switch gene Sex-lethal (Sxl) pre-mRNA specifically, similar to Sex-lethal protein (SXL). The polyuridine RNA binding enables SNF directly inhibit Sxl exon 3 splicing, as the dominant negative mutant SNF(1621) binds U1 snRNA but not polyuridine RNA. Unlike U1A, both RNA recognition motifs (RRMs) of SNF can recognize polyuridine RNA tracts independently, even though SNF and U1A share very high sequence identity and overall structure similarity. As SNF RRM1 tends to self-associate on the opposite side of the RNA binding surface, it is possible for SNF to bridge the formation of super-complexes between two introns flanking Sxl exon 3 or between a intron and U1 snRNP, which serves the molecular basis for SNF to directly regulate Sxl splicing. Taken together, a new functional model for SNF in Drosophila sex determination is proposed. The key of the new model is that SXL and SNF function similarly in promoting Sxl male-specific exon skipping with SNF being an auxiliary or backup to SXL, and it is the combined dose of SXL and SNF governs Drosophila sex determination.