title: siRNAs from an X-linked satellite repeat promote X-chromosome recognition in Drosophila melanogaster.
abstract: Highly differentiated sex chromosomes create a lethal imbalance in gene expression in one sex. To accommodate hemizygosity of the X chromosome in male fruit flies, expression of X-linked genes increases twofold. This is achieved by the male- specific lethal (MSL) complex, which modifies chromatin to increase expression. Mutations that disrupt the X localization of this complex decrease the expression of X-linked genes and reduce male survival. The mechanism that restricts the MSL complex to X chromatin is not understood. We recently reported that the siRNA pathway contributes to localization of the MSL complex, raising questions about the source of the siRNAs involved. The X-linked 1.688 g/cm(3) satellite related repeats (1.688(X) repeats) are restricted to the X chromosome and produce small RNA, making them an attractive candidate. We tested RNA from these repeats for a role in dosage compensation and found that ectopic expression of single-stranded RNAs from 1.688(X) repeats enhanced the male lethality of mutants with defective X recognition. In contrast, expression of double-stranded hairpin RNA from a 1.688(X) repeat generated abundant siRNA and dramatically increased male survival. Consistent with improved survival, X localization of the MSL complex was largely restored in these males. The striking distribution of 1.688(X) repeats, which are nearly exclusive to the X chromosome, suggests that these are cis-acting elements contributing to identification of X chromatin.
authors.affiliation: Department of Biological Sciences, Wayne State University, Detroit, MI 48020;
authors.forename: Debashish U
authors.initials: DU
authors.lastname: Menon
authors.affiliation: Molecular and Cellular Biology Department, Baylor College of Medicine, Houston, TX 77030; and.
authors.forename: Cristian
authors.initials: C
authors.lastname: Coarfa
authors.affiliation: Department of Biology and Biochemistry, University of Houston, Houston, TX 77204.
authors.forename: Weimin
authors.initials: W
authors.lastname: Xiao
authors.affiliation: Department of Biology and Biochemistry, University of Houston, Houston, TX 77204.
authors.forename: Preethi H
authors.initials: PH
authors.lastname: Gunaratne
authors.affiliation: Department of Biological Sciences, Wayne State University, Detroit, MI 48020; vmeller@biology.biosci.wayne.edu.
authors.forename: Victoria H
authors.initials: VH
authors.lastname: Meller
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D020029:Base Pairing; D001483:Base Sequence; D002874:Chromosome Mapping; D004276:DNA, Satellite / Q000235:genetics; D004268:DNA-Binding Proteins / Q000032:analysis; D004303:Dosage Compensation, Genetic; D004330:Drosophila / Q000145:classification / Q000235:genetics; D029721:Drosophila Proteins / Q000032:analysis / Q000235:genetics / Q000502:physiology; D004331:Drosophila melanogaster / Q000196:embryology / Q000235:genetics* / Q000254:growth & development / Q000648:ultrastructure; D022041:Euchromatin / Q000235:genetics; D005260:Female; D018507:Gene Expression Regulation, Developmental; D005804:Genes, Lethal; D007814:Larva; D008297:Male; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000032:analysis; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000096:biosynthesis / Q000235:genetics / Q000494:pharmacology / Q000502:physiology*; D016601:RNA-Binding Proteins / Q000235:genetics / Q000502:physiology; D012091:Repetitive Sequences, Nucleic Acid; D016415:Sequence Alignment; D012689:Sequence Homology, Nucleic Acid; D013045:Species Specificity; D020080:Tandem Repeat Sequences; D014157:Transcription Factors / Q000032:analysis / Q000235:genetics / Q000502:physiology; D019076:Transgenes; D014960:X Chromosome / Q000235:genetics*
chemical_list: D004276:DNA, Satellite; D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D022041:Euchromatin; D009687:Nuclear Proteins; C092595:Pabp2 protein, Drosophila; D034741:RNA, Small Interfering; D016601:RNA-Binding Proteins; D014157:Transcription Factors; C094166:msl-2 protein, Drosophila; C454144:roX1 protein, Drosophila
keywords: X chromosome recognition; dosage compensation; epigenetics; roX RNA; siRNA