Project description:Investigated the DNA binding specificity of the C-clamp of dnTCF1E Used a doxycycline inducible system to investigate the role of the C-clamp in the genome-wide binding of dnTCF1E. Induced dnTCF1EWT and dnTCF1Emut (C-clamp mutant that is null for C-clamp DNA binding) over 2 time points (2 hours and 9 hours). A 0 hour (no doxycycline, uninduced) control was also included.
Project description:To investigate the DNA binding specificity of the CLAMP protein, we have designed a custom PBM to interrogate the binding of CLAMP to DNA sequences extracted from the Drosophila melanogaster genome. Specific regions were extracted based on ChIP-seq data, motif occurence and proximity to gene transcription start sites.
Project description:To investigate the DNA binding specificity of the CLAMP protein, we have designed a custom PBM to interrogate the binding of CLAMP to DNA sequences extracted from the Drosophila melanogaster genome. Specific regions were extracted based on ChIP-seq data, motif occurence and proximity to gene transcription start sites. N-terminal GST-tagged protein samples were made for the C-terminal four and six zinc finger portions of the protein CLAMP; samples were made by in vitro transcription translation (IVT). IVT reaction mixtures for the two CLAMP constructs were applied directly to the PBM microarray and incubated for 1hour. Microarray-bound protein was fluorescently labeled using Alexa488-conjugated antibodies targeting GST, and the microarray was scanned in using a standard microarray scanner. Median fluorescence intensity over eight replicate probes was reported for each unique DNA sequence on the microarray.
Project description:CLAMP is a maternally deposited transcription factor binding to GA-rich genomic region. It recruits male-specific MSL (Male sex-lethal) complex on male X-chromosome that regulates dosage compensation in males, and competes with other GA-binding proteins like GAF, acting both synergistically as well as antagonistically in a context dependent manner. Considering CLAMP's male specific role in dosage compensation but ubiquitous expression in both males and females, what regulates differential binding of CLAMP is still unknown. Furthermore, ChiP-seq analysis has being long used to study protein-DNA interactions, however, since it uses physical force to shear DNA after protein capture, it is prone to both false negative and false positive peaks being called. To minimise these discrepancies, a recent CutnRun MNase based technique have being developed (Heinkoff Lab) which captures the DNA fragments bound to protein of interest. Due to higher accuracy in identifying the size and sequence of the protein bound DNA region, one can also identify monomeric or multimeric protein binding on the chromatin. We have used this technique to identify differential and shared CLAMP binding sites in male and female cells. We also compared CLAMP DNA binding peaks with CLAMP RNA binding peaks (iCLIP data) in male and female cells to understand sex-biased co-transcriptional RNA processing mechanism.
Project description:ChIP-seq was performed to compare binding the genome-wide binding profile of the CLAMP transcription factor in two different Drosophila species. ChIP seq experiments compare the binding profile of CLAMP in female larvae to identify conservation of its binding sequence.
Project description:We performed RNA-protein interaction study iCLIP, i.e single nucleotide resolution uv crosslinking and immunoprecipitation for DNA binding transcription factor CLAMP in different cellular fractions (Chromatin fraction, Nucleoplasmic fraction, Cytoplasmic Fraction) to explore sex-specific RNA binding properties of CLAMP in female (Kc) and Male (S2) cells
Project description:Long-range gene regulation is rare in bacteria and is confined to the classical DNA looping model. Here, we use a combination of biophysical approaches, including X-ray crystallography and single-molecule analysis, to show that long-range gene silencing on the plasmid RK2, a source of multidrug resistance across diverse Gram-negative bacteria, is achieved cooperatively by a DNA-sliding clamp, KorB, and a clamp-locking protein, KorA. We find that KorB is a CTPase clamp that can entrap and slide along DNA to reach distal target promoters. We resolved the tripartite crystal structure of a KorB-KorA-DNA co-complex, revealing that KorA latches KorB into a closed-clamp state. KorA thus stimulates repression by stalling KorB sliding at target promoters to occlude RNA polymerase holoenzymes. Altogether, our findings explain the mechanistic basis for KorB role-switching from a DNA-sliding clamp to a co-repressor, and provide a new paradigm for the long-range regulation of gene expression.
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:ChIP-seq and mRNA-seq experiments were performed to understand the role of the CLAMP protein in dosage compensation ChIP-seq experiments compared the binding profiles of CLAMP in male and female cells and mRNA-seq data to define the role of CLAMP in regulating genes on the X-chromosome
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.