Project description:Drosophila males double transcription of their single X chromosome to equalize X-linked gene expression with females, which carry two X chromosomes. Increased transcription requires the Male-Specific Lethal (MSL) complex. One of the primary functions of the MSL complex is thought to be enrichment of H4Ac16 on the male X chromosome, a modification linked to elevated transcription. The roX1 and roX2 RNAs are essential but redundant components of the MSL complex. Simultaneous removal of both roX RNAs reduces MSL X-localization and leads to ectopic binding of these proteins at autosomal sites and to the chromocenter. Some H4Ac16 accumulates at these ectopic sites in roX1- roX2- males, suggesting the possibility of increased expression. The global effect of roX mutations on gene expression was measured by microarray analysis. We found that expression of the X chromosome was decreased by 26% in roX1- roX2- male larvae, supporting the involvement of roX RNAs in the up-regulation of X-linked genes. This finding is broadly comparable to reports of reduced X chromosome expression following msl2 RNAi knockdown in S2 cells. In spite of strong MSL binding and H4Ac16 accumulation at autosomal sites in roX1- roX2- males, enhanced gene expression could not be detected at these sites by microarray analysis or reverse northern blotting. Thus, failure to compensate X-linked genes, rather than inappropriate up-regulation of autosomal genes at ectopic sites of MSL binding, appears to cause male lethality upon loss of roX RNAs. Experiment Overall Design: Total RNA was prepared from groups of 50 third instar larvae by TRIzol (Invitrogen) extraction and purified using the RNeasy kit (Qiagen). Three independent RNA preparations for each genotype served as templates for probe synthesis. Affymetrix Drosophila Genome 2.0 chips were hybridized to these probes (Santa Clara, CA). The affymertrix Drosophila annotation of December 2004 was used to map genes to their cytological locations. Genes were filtered for present/absent calls by a PM-MM (Perfect match- Mismatch) comparison. Autosomal transcripts were normalized on a chip-by-chip basis to bring their median values to 100. The identical degree of adjustment was used to normalize X-linked transcripts. Changes in gene expression were determined by comparing the mean signal intensities of genes on arrays hybridized with roX1SMC17A roX2- probes to those hybridized with roX1+ roX2- probes.
Project description:The Drosophila male-specific lethal (MSL) complex binds to the male X chromosome to activate transcription, and consists of five proteins, MSL1, MSL2, MSL3, MOF, MLE, and two roX RNAs. The MLE helicase remodels the roX lncRNAs, enabling the lncRNA-mediated assembly of the Drosophila dosage compensation complex. MSL2 is expressed only in males and interacts with the N-terminal zinc-finger of the transcription factor CLAMP that is important for specific recruitment of the MSL complex on the male X chromosome. Here we found that the unstructured C-terminal region of MLE interacts with 6-7 zinc-finger domains of CLAMP. In vitro 4-5 zinc fingers are critical for specific DNA-binding of CLAMP with GA-repeats, which constitute the core motif at the high affinity binding sites for MSL proteins. Deletion of the Clamp Binding Domain (CBD) in MLE results in decreasing of MSL proteins association with male X chromosome and increasing of male lethality. These results suggest that interactions of unstructured regions in MSL2 and MLE with CLAMP zinc finger domains are important for the specific recruitment of the MSL complex on the male X chromosome.
Project description:We used the DamID method to systematically identify the binding sites of Ecdysone Receptor and its heterodimeric partner USP across the whole genome in Drosophila Kc cells. We find that the EcR sites are a subset of the USP sites and that only a proportion are ecdysone regulated from an accompanying ecdysone profiling study. The role of EcR/USP in the ecdysone network appears to be coordinated by the recruitment of many transcription factors as well as signaling molecules. Keywords: DamID, chromatin profiling, DNA microarray In this study we mapped the genomic binding sites of steroid hormone nuclear receptor EcR and USP in Kc167 cells using the DamID method. DamID involves the low level expression of a fusion protein consisting of DNA adenine methyltransferase (Dam) and a chromatin protein of interest. This fusion protein is targeted to the native binding sites of the chromatin protein, where Dam methylates adenines in the surrounding DNA. The methylated DNA fragments were isolated and amplified by selective PCR, labeled with a fluorescent dye and hybridized to whole genome tiling microarrays. In this study,experiments were done with samples obtained from independent experiments and include dye swaps.
Project description:Drosophila males double transcription of their single X chromosome to equalize X-linked gene expression with females, which carry two X chromosomes. Increased transcription requires the Male-Specific Lethal (MSL) complex. One of the primary functions of the MSL complex is thought to be enrichment of H4Ac16 on the male X chromosome, a modification linked to elevated transcription. The roX1 and roX2 RNAs are essential but redundant components of the MSL complex. Simultaneous removal of both roX RNAs reduces MSL X-localization and leads to ectopic binding of these proteins at autosomal sites and to the chromocenter. Some H4Ac16 accumulates at these ectopic sites in roX1- roX2- males, suggesting the possibility of increased expression. The global effect of roX mutations on gene expression was measured by microarray analysis. We found that expression of the X chromosome was decreased by 26% in roX1- roX2- male larvae, supporting the involvement of roX RNAs in the up-regulation of X-linked genes. This finding is broadly comparable to reports of reduced X chromosome expression following msl2 RNAi knockdown in S2 cells. In spite of strong MSL binding and H4Ac16 accumulation at autosomal sites in roX1- roX2- males, enhanced gene expression could not be detected at these sites by microarray analysis or reverse northern blotting. Thus, failure to compensate X-linked genes, rather than inappropriate up-regulation of autosomal genes at ectopic sites of MSL binding, appears to cause male lethality upon loss of roX RNAs. Keywords: effect of roX1-roX2- mutant on gene expression
Project description:Active genes on the X chromosome of Drosophila males are upregulated by the Male-specific lethal (MSL) complex containing five MSL proteins and two non-coding roX RNAs. To probe the targeting mechanism, we have solved the structure of the MSL3 chromodomain, designed point mutations in key residues that disrupt putative methyl-lysine recognition, and tested their effect on full length MSL3 function. Transgenic males expressing these site-directed point mutants or MSL3short, a naturally occurring MSL3 form lacking the chromodomain, are unhealthy and developmentally delayed. Genomewide analyses of the binding patterns of these mutants support a two-step model: the first step is chromodomain-independent association with “chromatin entry sites” carrying GA-rich MSL recognition elements (MREs). The second step involves spreading from entry sites to the majority of active genes on the X. Either deleting or introducing point mutations in the MSL3 chromodomain disrupts this second step. In vitro studies demonstrate that chromodomain mutants have diminished interaction with recombinant nucleosomes methylated at H3K36. We propose that MSL spreading depends, to a large extent, on the integrity of the MSL3 chromodomain to interact with lysine-methylated nucleosomes.
Project description:Genome-wide identification of the binding sites of the Drosophila transcription factors Achaete, Asense, E(spl)m3-HLH and Senseless in wing imaginal cells using DamID profiling.
Project description:In Drosophila, the global increase in transcription from the X chromosome in males to compensate for its monosomy is mediated by the male-specific-lethal complex (MSL-C) consisting of five proteins and two non-coding RNAs, roX1 and roX2. After an initial sequence dependent recognition by the MSL-C of 150-300 high affinity sites, the spreading to the majority of the X-linked genes depends on local MSL-C concentration and active transcription. Here we ask whether any additional RNA species are associated to the MSL-C. No additional roX were found but a strong association was found between the msl2 mRNA and the MSL-C. Based on our results we propose a model in which a non-chromatin associated partial or complete MSL-C titrates newly transcribed msl2 mRNA and thus feed-back regulates the amount of available MSL-C. In total 12 samples; 4 Input files (4 different conditions) with the corresponding 8 RIP samples (2 different antibodies, same 4 conditions as Input)