Project description:We performed ChIP-sequencing with antibodies targeting Su(H) to assess the genomic binding sites of this protein in S2 cells as a reference for the comparison with published data of this cell line
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:Identification of the interaction partners of the protein ecdysoneless (Ecd) in Drosophila melanogaster S2 cells as well as profiling of the changes in binding for mutant, truncated Ecd del34 protein.
Project description:ChIP-chip experiments with NimbleGen whole-genome tiling arrays to compare Su(Hw), dCTCF, BEAF, and CP190 localization on DNA in Kc and Mbn2 cells revealed that BEAF is a third subclass of CP190-containing insulators. The DNA binding proteins, Su(Hw), dCTCF, and BEAF show unique distribution patterns with respect to the location and expression level of genes, suggesting diverse roles for these three subclasses of insulators in genome organization. Notably, cell line specific localization sites for all three DNA binding proteins as well as CP190 indicate multiple levels at which insulators can be regulated to affect gene expression.
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