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:A key model for understanding how large transcription complexes are targeted is the Drosophila dosage compensation system in which the Male-Specific Lethal (MSL) transcription complex specifically identifies and regulates the male X-chromosome. MSL complex is targeted to GA-containing sequences, but the most well-studied GA-binding transcription factor, GAGA Associated Factor (GAF), does not physically associate with MSL complex. Instead the Chromatin Linked Adapter for MSL Proteins (CLAMP) zinc-finger protein specifically targets MSL complex to GA-rich sequences on the X-chromosome. Here, we compare the binding relationships of CLAMP, GAF, and the MSL3 dosage compensation complex protein using ChIP-seq.
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.
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)
Project description:In Drosophila, two chromosome-wide compensatory systems have been characterized; the dosage compensation system acting on the male X-chromosome and the chromosome specific regulation of genes located on the heterochromatic 4th chromosome. Dosage compensation in Drosophila is accomplished by hypertranscription of the single male X-chromosome mediated by the MSL-complex. The mechanism for this compensation is suggested to be an MSL-complex mediated enhanced transcriptional elongation while the mechanism for the compensation mediated by Painting of fourth (POF) on the 4th chromosome has remained elusive. Here we show that POF binds to nascent RNA and this binding is associated with an increase in amount of chromosome 4 transcripts. Furthermore, genes located on the 4th chromosome are enriched in binding of the nucleoplasmic nucleporin component NUP98 and this enrichment correlates to increased POF binding. We also show that genes located in heterochromatic regions have a shorter transition time from site of transcription and to the nuclear envelope. Our current work broadens the understanding about how genes in heterochromatic regions can overcome the repressive influence of their hostile environment.
Project description:Drosophila MSL complex binds the single male X chromosome to upregulate gene expression to equal that from the two female X chromosomes. However, it has been puzzling that ~25% of transcribed genes on the X do not stably recruit MSL complex. Here, we find that almost all active genes on the X are associated with robust H4 Lys16 acetylation (H4K16ac), the histone modification catalyzed by MSL complex. The distribution of H4K16ac is much broader than that of MSL complex, and our results favor the idea that chromosome-wide H4K16ac reflects transient association of MSL complex, occurring through spreading or chromosomal looping. Our results parallel those of localized Polycomb repressive complex and its more broadly distributed H3K27me3 chromatin mark, suggesting a common principle for the establishment of active and silenced chromatin domains
Project description:X-chromosome dosage compensation in Drosophila requires the male-specific lethal (MSL) complex, which up-regulates gene expression from the single male X chromosome. Here, we define X-chromosome-specific MSL binding at high resolution in two male cell lines and in late-stage embryos. We find that the MSL complex is highly enriched over most expressed genes, with binding biased toward the 3' end of transcription units. The binding patterns are largely similar in the distinct cell types, with ~600 genes clearly bound in all three cases. Genes identified as clearly bound in one cell type and not in another indicate that attraction of MSL complex correlates with expression state. Thus, sequence alone is not sufficient to explain MSL targeting. We propose that the MSL complex recognizes most X-linked genes, but only in the context of chromatin factors or modifications indicative of active transcription. Distinguishing expressed genes from the bulk of the genome is likely to be an important function common to many chromatin organizing and modifying activities. Keywords: ChIP-chip
Project description:In Drosophila, two chromosome-wide compensatory systems have been characterized; the dosage compensation system acting on the male X-chromosome and the chromosome specific regulation of genes located on the heterochromatic 4th chromosome. Dosage compensation in Drosophila is accomplished by hypertranscription of the single male X-chromosome mediated by the MSL-complex. The mechanism for this compensation is suggested to be an MSL-complex mediated enhanced transcriptional elongation while the mechanism for the compensation mediated by Painting of fourth (POF) on the 4th chromosome has remained elusive. Here we show that POF binds to nascent RNA and this binding is associated with an increase in amount of chromosome 4 transcripts. Furthermore, genes located on the 4th chromosome are enriched in binding of the nucleoplasmic nucleporin component NUP98 and this enrichment correlates to increased POF binding. We also show that genes located in heterochromatic regions have a shorter transition time from site of transcription and to the nuclear envelope. Our current work broadens the understanding about how genes in heterochromatic regions can overcome the repressive influence of their hostile environment. Pof mutant vs. wild type, 3 replicates
Project description:In Drosophila, two chromosome-wide compensatory systems have been characterized; the dosage compensation system acting on the male X-chromosome and the chromosome specific regulation of genes located on the heterochromatic 4th chromosome. Dosage compensation in Drosophila is accomplished by hypertranscription of the single male X-chromosome mediated by the MSL-complex. The mechanism for this compensation is suggested to be an MSL-complex mediated enhanced transcriptional elongation while the mechanism for the compensation mediated by Painting of fourth (POF) on the 4th chromosome has remained elusive. Here we show that POF binds to nascent RNA and this binding is associated with an increase in amount of chromosome 4 transcripts. Furthermore, genes located on the 4th chromosome are enriched in binding of the nucleoplasmic nucleporin component NUP98 and this enrichment correlates to increased POF binding. We also show that genes located in heterochromatic regions have a shorter transition time from site of transcription and to the nuclear envelope. Our current work broadens the understanding about how genes in heterochromatic regions can overcome the repressive influence of their hostile environment.