Project description:There is considerable evidence that insulator elements are likely to play a key role in the organisation of the regulatory architecture of the genome. In Drosophila, one of the best studied insulator elements is the gypsy insulator in the gypsy retrotransposon whose function is dependent on the Su(Hw) Zn-finger DNA binding protein. Although there are several hundred Su(Hw) sites in the genome which are proposed to act as endogenous insulator elements, analysis of the role of the Su(Hw) protein has focussed on the gypsy insulator and few endogenous sites have yet been identified. We have used chromatin immunopurification coupled to genomic microarray analysis to identify Su(Hw) binding sites within a representative region of the Drosophila genome; the 3MB Adh region on chromosome 2L. We have located about 60 Su(Hw) binding sites across this region and this has enabled us to construct a robust new Su(Hw) binding site consensus based on these in vivo sites. In contrast to the gypsy insulator which contains 12 Su(Hw) binding sites within 340bp, the endogenous sites are not present in clusters. We identify two key features of these endogenous Su(Hw) sites. Firstly, in contrast to most analyses of DNA binding protein specificity, we find that strong matches to the binding consensus are good predictors of binding site occupancy. Secondly, examination of Su(Hw) binding site occupancy in 0-20hr embryos, 3rd larval instar brains or 3rd larval imaginal discs reveals a constant pattern of Su(Hw) binding indicating that most , if not all Su(Hw) sites are constitutively occupied. These two features support a constant genomic architectural role for the Su(Hw) protein. Keywords: ChIP-chip
Project description:Suppressor of Hairy-wing [Su(Hw)] is a globally expressed twelve-zinc finger transcription factor in Drosophila. Su(Hw) is well-known for its role in establishing the gypsy insulator within the gypsy retrotransposon. A direct role of Su(Hw) in gene activation and repression was uncovered through the study in the Drosophila oogenesis, revealing that Su(Hw)-dependent repression of neuronal genes is essential for egg production. Motivated from the spatially restricted expression of Su(Hw) in the testis, we investigated the role of Su(Hw) in spermatogenesis. We discovered that Su(Hw) is required for sperm development and male fertility. Data presented here examined the transcriptional role of Su(Hw) in the Drosophila testis. These studies identified ~400 genes with altered expression in the absence of Su(Hw). Coupled with whole-genome Su(Hw) binding profiles, we identified 145 direct targets of Su(Hw) regulation, of which ~80% show increased transcription upon Su(Hw) loss. Upregulated Su(Hw) targets are enriched for neuronal expression, emphasizing that Su(Hw) represents a functional homolog of mammalian REST that represses neuronal gene expression in non-neuronal tissues.
Project description:Suppressor of Hairy-wing [Su(Hw)] is a multi-zinc finger DNA binding factor required for gypsy insulator function and female germline development in Drosophila. The enhancer-blocking and barrier functions of the gypsy retrotransposon involve Su(Hw) binding to twelve clustered Su(Hw) binding sites (SBSs) and recruitment of the Centrosomal Protein of 190 kD (CP190) and Modifier of mdg4 67.2 kD isoform (Mod67.2) insulator proteins. In contrast, the Su(Hw) germline function involves binding to non-clustered genomic SBSs and does not require CP190 or Mod67.2. Here, we use genome-wide expression analyses in the ovary to identify the first Su(Hw) regulated target genes.
Project description:The twelve zinc finger Suppressor of Hairy-wing [Su(Hw)] protein binds thousands of sites in Drosophila genome and is essential for the function of the gypsy insulator. Loss of the globally expressed Su(Hw) protein causes female sterility due to tissue-specific defect limited to female germline. Using chromatin immunoprecipitation followed by next generation sequencing (ChIP-Seq), we determine the extent of tissue-specific binding of Su(Hw) in Drosophila ovary. We demonstrate that Su(Hw) binding sites (SBSs) are largely constitutively occupied in the germline and soma. Our analyses indicate that SBSs fall into several non-uniform classes, as determined by the partner protein distribution and DNA sequence conservation. Further, we show that only a subset of SBSs is required for the female fertility. These sites are maintained in the su(Hw)f zinc finger 10 mutant background, which is fertile but does not support gypsy insulator function. Together, our data are consistent with the model where Su(Hw) serves multiple regulatory roles in the genome, and contribute to understanding of how loss of a single zinc finger affects chromosome localization of a DNA binding protein. Examination of Su(Hw) localization in the ovaries of less than 6 hour old wild type and su(Hw)f mutant Drosophila females
Project description:The twelve zinc finger Suppressor of Hairy-wing [Su(Hw)] protein binds thousands of sites in Drosophila genome and is essential for the function of the gypsy insulator. Loss of the globally expressed Su(Hw) protein causes female sterility due to tissue-specific defect limited to female germline. Using chromatin immunoprecipitation followed by next generation sequencing (ChIP-Seq), we determine the extent of tissue-specific binding of Su(Hw) in Drosophila ovary. We demonstrate that Su(Hw) binding sites (SBSs) are largely constitutively occupied in the germline and soma. Our analyses indicate that SBSs fall into several non-uniform classes, as determined by the partner protein distribution and DNA sequence conservation. Further, we show that only a subset of SBSs is required for the female fertility. These sites are maintained in the su(Hw)f zinc finger 10 mutant background, which is fertile but does not support gypsy insulator function. Together, our data are consistent with the model where Su(Hw) serves multiple regulatory roles in the genome, and contribute to understanding of how loss of a single zinc finger affects chromosome localization of a DNA binding protein.
Project description:Suppressor of Hairy wing (Su(Hw)) is an insulator protein that participates in regulating chromatin architecture and gene repression in Drosophila. In previous studies we have shown that Su(Hw) is also required for pre-replication complex (pre-RC) recruitment on Su(Hw)-bound sites (SBSs) in Drosophila S2 cells and pupa. Here, we describe the effect of Su(Hw) on developmentally regulated amplification of 66D and 7F Drosophila amplicons in follicle cells (DAFCs), widely used as models in replication studies. We show Su(Hw) binding co-localizes with all known DAFCs in Drosophila ovaries, whereas disruption of Su(Hw) binding to 66D and 7F DAFCs causes a two-fold decrease in the amplification of these loci. The complete loss of Su(Hw) binding to chromatin violates pre-RC recruitment to all amplification regulatory regions of 66D and 7F loci at early oogenesis (prior to DAFCs amplification). These changes coincide with a considerable Su(Hw)-dependent condensation of chromatin at 66D and 7F loci. Although we observed the Brm, ISWI, Mi-2, and CHD1 chromatin remodelers at SBSs genome wide, their remodeler activity does not appear to be responsible for chromatin decondensation at the 66D and 7F amplification regulatory regions. We have discovered that, in addition to the CBP/Nejire and Chameau histone acetyltransferases, the Gcn5 acetyltransferase binds to 66D and 7F DAFCs at SBSs and is dependent on Su(Hw). We propose that the main function of Su(Hw) in developmental amplification of 66D and 7F DAFCs is to establish a chromatin structure that is permissive to pre-RC recruitment.
Project description:Suppressor of Hairy-wing [Su(Hw)] is a multi-zinc finger DNA binding factor required for gypsy insulator function and female germline development in Drosophila. The enhancer-blocking and barrier functions of the gypsy retrotransposon involve Su(Hw) binding to twelve clustered Su(Hw) binding sites (SBSs) and recruitment of the Centrosomal Protein of 190 kD (CP190) and Modifier of mdg4 67.2 kD isoform (Mod67.2) insulator proteins. In contrast, the Su(Hw) germline function involves binding to non-clustered genomic SBSs and does not require CP190 or Mod67.2. Here, we use genome-wide expression analyses in the ovary to identify the first Su(Hw) regulated target genes. Ovaries for RNA isolation were dissected from 4-6 hour old virgin females of wild type (Canton S and BL15598) and su(Hw) null sterile mutants (su(Hw)A2663/v and su(Hw)Pb/2) Drosophila melanogaster. At this stage of development, ovaries only contain egg chamber stages 1-8. Loss of Su(Hw) causes apoptosis at stage 9. Thus, the experimental design compares transcriptional changes in the ovary prior to induction nof apoptosis in su(Hw) mutants.
Project description:Insulators delimit independent transcriptional domains within genomes by constraining enhancer and silencer action. These transcriptional effects depend upon DNA recognition by insulator binding proteins that recruit partners that protect against inappropriate long range modulation of non-target promoters. Insulator binding proteins are broadly expressed during development, with largely constitutive binding to thousands of genomic sites. Yet, tissue-specific transcriptional changes result from the loss of individual insulator binding proteins. To understand the molecular basis for such effects, we are studying the classic Drosophila insulator protein Suppressor of Hairy-wing [Su(Hw)]. Genetic studies show that loss of this broadly expressed insulator protein prevents oocyte development. To determine the basis for the block in oogenesis, we coupled transcriptional analyses in su(Hw) mutant ovaries with genome-wide definition of Su(Hw) binding in this tissue. These studies identified 71 direct targets of Su(Hw) regulation, with nearly 70% of these genes showing increased RNA accumulation when Su(Hw) is lost. Surprisingly, derepressed Su(Hw) target genes correspond to genes normally highly expressed in neural tissues, suggesting that Su(Hw) has a critical role in silencing neural genes in the ovary. Support for this postulate was obtained by genetic studies. We found that oocyte production was restored in su(Hw) mutant females that carry a deletion of one allele of the elav family RNA binding protein 9 (Rbp9) gene. These su(Hw) null oocytes can be fertilized, with evidence that embryos lacking Su(Hw) show compromised development. Our studies extend the known transcriptional activities of Su(Hw), indicating that Su(Hw) can function as an insulator, activator and repressor, the latter function being essential for oogenesis. These findings highlight that insulator proteins are versatile transcriptional regulatory proteins, suggesting that tissue specific contributions to transcription result from direct regulation of individual genes.