Project description:Chromatin insulators and Polycomb group (PcG) complexes control nuclear organization to effect changes in gene expression. In Drosophila, RNA silencing pathways influence long range interactions mediated by PcG proteins and nuclear localization of the gypsy insulator; however, the underlying mechanisms are unknown. Here, we identify a singular requirement for Argonaute2 (AGO2) for the activity of the CCCTC-binding factor (CTCF)/Centrosomal protein 190 (CP190) dependent Fab-8 insulator. AGO2 and CP190 interact physically, and genome wide localization of AGO2 by chromatin immunoprecipitation and sequencing (ChIP-seq) reveals extensive colocalization of AGO2 with insulators and Polycomb Response Elements (PREs) but minimal overlap with regions of endogenous small interfering RNA (endo-siRNA) production. Finally, depletion of either CTCF or CP190 results in loss of AGO2 association with insulators, PREs, and other cis-regulatory regions. Our findings suggest that Dicer-independent recruitment of AGO2 to chromatin by insulator proteins promotes the definition of transcriptional domains throughout the genome. ChIP-seq of AGO2 in two Drosophila cell types (S2 and S3)
Project description:Chromatin insulators and Polycomb group (PcG) complexes control nuclear organization to effect changes in gene expression. In Drosophila, RNA silencing pathways influence long range interactions mediated by PcG proteins and nuclear localization of the gypsy insulator; however, the underlying mechanisms are unknown. Here, we identify a singular requirement for Argonaute2 (AGO2) for the activity of the CCCTC-binding factor (CTCF)/Centrosomal protein 190 (CP190) dependent Fab-8 insulator. AGO2 and CP190 interact physically, and genome wide localization of AGO2 by chromatin immunoprecipitation and sequencing (ChIP-seq) reveals extensive colocalization of AGO2 with insulators and Polycomb Response Elements (PREs) but minimal overlap with regions of endogenous small interfering RNA (endo-siRNA) production. Finally, depletion of either CTCF or CP190 results in loss of AGO2 association with insulators, PREs, and other cis-regulatory regions. Our findings suggest that Dicer-independent recruitment of AGO2 to chromatin by insulator proteins promotes the definition of transcriptional domains throughout the genome.
Project description:This study examines the changes in genes expression that occur in Drosophila melanogaster during the ecdysone response as well as during RNAi knockdown of the insulator protein, CP190. Analysis was performed in Kc cells after 0, 3, and 48 hours of ecdysone treatment in the presence of either control or CP190 knockdown.
Project description:CTCF and Cp190 proteins are implicated at many insulator elements throughout Drosophila genome. Here we compared Hi-C maps, transcriptomes and binding of multiple insulator proteins in cultured Drosophila cells derived from CTCF-KO, Cp190-KO and control embryos.
Project description:CTCF and Cp190 proteins are implicated at many insulator elements throughout Drosophila genome. Here we compared Hi-C maps, transcriptomes and binding of multiple insulator proteins in cultured Drosophila cells derived from CTCF-KO, Cp190-KO and control embryos.
Project description:CTCF and Cp190 proteins are implicated at many insulator elements throughout Drosophila genome. Here we compared Hi-C maps, transcriptomes and binding of multiple insulator proteins in cultured Drosophila cells derived from CTCF-KO, Cp190-KO and control embryos.
Project description:Chromatin insulators are DNA-protein complexes that establish higher order independent DNA domains to influence transcriptional regulation. Insulators are defined by two different functions: they can block communication between an enhancer and a promoter and also act as a barrier between heterochromatin and euchromatin. In Drosophila, the gypsy-insulator complex contains three core components: Su(Hw), CP190 and Mod(mdg4)67.2. Here we identify a novel role for Chromatin-linked adaptor for MSL proteins (CLAMP) in promoting gypsy chromatin insulator function. When Clamp is depleted by RNAi, gypsy-dependent enhancer blocking activity decreases and barrier activity is reduced in all tissues. Furthermore, Clamp RNAi knockdowns and mutation result in disorganized insulator complex localization in the nucleus. Co-immunoprecipitation experiments showed that CLAMP physically associates with core gypsy-insulator proteins. Co-localization of CLAMP with gypsy components on polytene chromosomes and ChIP-seq analysis demonstrates co-localization of CLAMP with a subset of insulator sites across the genome. Thus, our findings suggest a ubiquitous, genome-wide role for CLAMP in promoting gypsy-dependent chromatin insulator activity.
Project description:Chromatin insulators are DNA-protein complexes that establish higher order independent DNA domains to influence transcriptional regulation. Insulators are defined by two different functions: they can block communication between an enhancer and a promoter and also act as a barrier between heterochromatin and euchromatin. In Drosophila, the gypsy-insulator complex contains three core components: Su(Hw), CP190 and Mod(mdg4)67.2. Here we identify a novel role for Chromatin-linked adaptor for MSL proteins (CLAMP) in promoting gypsy chromatin insulator function. When Clamp is depleted by RNAi, gypsy-dependent enhancer blocking activity decreases and barrier activity is reduced in all tissues. Furthermore, Clamp RNAi knockdowns and mutation result in disorganized insulator complex localization in the nucleus. Co-immunoprecipitation experiments showed that CLAMP physically associates with core gypsy-insulator proteins. Co-localization of CLAMP with gypsy components on polytene chromosomes and ChIP-seq analysis demonstrates co-localization of CLAMP with a subset of insulator sites across the genome. Thus, our findings suggest a ubiquitous, genome-wide role for CLAMP in promoting gypsy-dependent chromatin insulator activity.
Project description:Chromatin insulators are DNA-protein complexes that can prevent the spread of repressive chromatin and block communication between enhancers and promoters to regulate gene expression. In Drosophila, the gypsy chromatin insulator complex consists of three core proteins: CP190, Su(Hw), and Mod(mdg4)67.2. These factors concentrate at nuclear foci termed insulator bodies, and their normal localization is correlated with proper insulator function. Here, we identified NURF301/E(bx), a nucleosome remodeling factor, as a novel regulator of gypsy insulator body localization through a high-throughput RNAi imaging screen. NURF301 promotes gypsy-dependent insulator barrier activity and physically interacts with gypsy insulator proteins. Using ChIP-seq, we found that NURF301 co-localizes with insulator proteins genome-wide, and NURF301 promotes chromatin association of Su(Hw) and CP190 at gypsy insulator binding sites. These effects correlate with NURF301-dependent nucleosome repositioning. At the same time, CP190 and Su(Hw) are also required for recruitment of NURF301 to chromatin. Finally, Oligopaint FISH combined with immunofluorescence revealed that NURF301 promotes 3D contact between insulator bodies and gypsy binding site DNA, and NURF301 is required for proper nuclear positioning of gypsy binding sites. Our data provide new insights into how a nucleosome remodeling factor and insulator proteins cooperatively contribute to nuclear organization.