N-terminus of Drosophila MSL1 is critical for dosage compensation
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ABSTRACT: The male-specific dosage compensation complex (DCC), which consists of five proteins and two non-coding roX RNAs, is necessary for the transcriptional enhancement of X-linked genes to compensate for the sex chromosome monosomy in Drosophila XY males, compared with XX females. The MSL1 and MSL2 proteins form the heterotetrameric core of DCC and are critical for the specific recruitment of the DCC to the high-affinity “entry” sites (HAS) on the X chromosome. Here we demonstrated that the N-terminal region of MSL1 is critical for its stability and functions. Amino acid deletions and substitutions in the N-terminal region of MSL1 strongly affect both interaction with roX2 RNA and DCC binding to HAS on the X chromosome. In particular, substitution of the conserved N-terminal amino-acids 3-7 in MSL1GS has an affect on dosage compensation similar to inactivation of genes encoding roX RNAs. MSL1GS binds to promoters like MSL1WT but does not co-bind with MSL2 and MSL3 to X chromosomal HAS. However, over-expression of MSL2 partially restores the functional activity of MSL1GS in dosage compensation. Thus, the interaction of MSL1 with roX RNA is critical for the efficient assembly of DCCs on HAS of the male X chromosome.
Project description:The male-specific lethal dosage compensation complex (MSL complex or DCC), which consists of five proteins and two non-coding roX RNAs, is necessary for the transcriptional enhancement of X-linked genes to compensate for the sex chromosome monosomy in Drosophila XY males, compared with XX females. MSL2 is a single protein component of the DCC that is expressed only in males and is essential for the specific recruitment of the DCC to the high-affinity “entry” sites (HASs) on the X chromosome. MSL2, together with MSL1, forms the heterotetrameric DCC core. Here, we demonstrated that the N-terminal unstructured region of MSL1 interacts with many different DNA-binding proteins that contain clusters of the C2H2 zinc-finger domains. Amino acid deletions in the N-terminal region of MSL1 strongly affect the binding of the DCC to the HASs on the male X chromosome. However, the binding of MSL2 to autosomal promoters was unaffected by amino acid deletions in MSL1. Males expressing mutant variants of MSL1 died during the larvae stage, demonstrating the critical role played by the N-terminal region in DCC activity. Our results suggest that MSL1 interacts with a variety of DNA-binding proteins to increase the specificity of DCC recruitment to the male X chromosome.
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:Confinement of the X chromosome into a territory for dosage compensation (DC) is a prime example of subnuclear compartmentalization for transcription regulation at the megabase scale. In D. melanogaster, two sex-specific non-coding (nc) RNAs roX1 and roX2 are transcribed from the X chromosome. They associate with the Male-specific lethal (MSL) complex, which by acetylating histone H4 lysine 16 (H4K16ac) confers approximately 2-fold upregulated expression of male X-linked genes. Current models explain X-over-autosome specificity based on the MSL2 subunit recognizing cis-regulatory DNA high-affinity sites (HAS). However, HAS motifs are also found on autosomes, indicating that additional factors have evolved to confer stable association of the MSL complex with the X. Here, we show that the low-complexity C-terminal domain (CTD) of MSL2 renders its recruitment to the X chromosome sensitive to roX ncRNAs. roX-MSL2-CTD form a stably condensated state, and functional analyses in Drosophila and mammalian cells reveal the critical importance of their interplay for DC in vivo. Replacing the CTD of mammalian MSL2 with that from Drosophila and expressing roX in cis is sufficient to nucleate ectopic DC in mammalian cells. Thus, the condensating nature of roX-MSL2CTD is the primary determinant for specific compartmentalization of the X in Drosophila.
Project description:Confinement of the X chromosome into a territory for dosage compensation (DC) is a prime example of subnuclear compartmentalization for transcription regulation at the megabase scale. In D. melanogaster, two sex-specific non-coding (nc) RNAs roX1 and roX2 are transcribed from the X chromosome. They associate with the Male-specific lethal (MSL) complex, which by acetylating histone H4 lysine 16 (H4K16ac) confers approximately 2-fold upregulated expression of male X-linked genes. Current models explain X-over-autosome specificity based on the MSL2 subunit recognizing cis-regulatory DNA high-affinity sites (HAS). However, HAS motifs are also found on autosomes, indicating that additional factors have evolved to confer stable association of the MSL complex with the X. Here, we show that the low-complexity C-terminal domain (CTD) of MSL2 renders its recruitment to the X chromosome sensitive to roX ncRNAs. roX-MSL2-CTD form a stably condensated state, and functional analyses in Drosophila and mammalian cells reveal the critical importance of their interplay for DC in vivo. Replacing the CTD of mammalian MSL2 with that from Drosophila and expressing roX in cis is sufficient to nucleate ectopic DC in mammalian cells. Thus, the condensating nature of roX-MSL2CTD is the primary determinant for specific compartmentalization of the X in Drosophila.
Project description:Confinement of the X chromosome into a territory for dosage compensation (DC) is a prime example of subnuclear compartmentalization for transcription regulation at the megabase scale. In D. melanogaster, two sex-specific non-coding (nc) RNAs roX1 and roX2 are transcribed from the X chromosome. They associate with the Male-specific lethal (MSL) complex, which by acetylating histone H4 lysine 16 (H4K16ac) confers approximately 2-fold upregulated expression of male X-linked genes. Current models explain X-over-autosome specificity based on the MSL2 subunit recognizing cis-regulatory DNA high-affinity sites (HAS). However, HAS motifs are also found on autosomes, indicating that additional factors have evolved to confer stable association of the MSL complex with the X. Here, we show that the low-complexity C-terminal domain (CTD) of MSL2 renders its recruitment to the X chromosome sensitive to roX ncRNAs. roX-MSL2-CTD form a stably condensated state, and functional analyses in Drosophila and mammalian cells reveal the critical importance of their interplay for DC in vivo. Replacing the CTD of mammalian MSL2 with that from Drosophila and expressing roX in cis is sufficient to nucleate ectopic DC in mammalian cells. Thus, the condensating nature of roX-MSL2CTD is the primary determinant for specific compartmentalization of the X in Drosophila.
Project description:Confinement of the X chromosome into a territory for dosage compensation (DC) is a prime example of subnuclear compartmentalization for transcription regulation at the megabase scale. In D. melanogaster, two sex-specific non-coding (nc) RNAs roX1 and roX2 are transcribed from the X chromosome. They associate with the Male-specific lethal (MSL) complex, which by acetylating histone H4 lysine 16 (H4K16ac) confers approximately 2-fold upregulated expression of male X-linked genes. Current models explain X-over-autosome specificity based on the MSL2 subunit recognizing cis-regulatory DNA high-affinity sites (HAS). However, HAS motifs are also found on autosomes, indicating that additional factors have evolved to confer stable association of the MSL complex with the X. Here, we show that the low-complexity C-terminal domain (CTD) of MSL2 renders its recruitment to the X chromosome sensitive to roX ncRNAs. roX-MSL2-CTD form a stably condensated state, and functional analyses in Drosophila and mammalian cells reveal the critical importance of their interplay for DC in vivo. Replacing the CTD of mammalian MSL2 with that from Drosophila and expressing roX in cis is sufficient to nucleate ectopic DC in mammalian cells. Thus, the condensating nature of roX-MSL2CTD is the primary determinant for specific compartmentalization of the X in Drosophila. This SuperSeries is composed of the SubSeries listed below.
Project description:The dosage compensation complex (DCC) of Drosophila identifies its X chromosomal binding sites with exquisite selectivity. The principles that assure this vital targeting are known from the D. melanogaster model: DCC-intrinsic specificity of DNA binding, cooperativity with the CLAMP protein, and non-coding roX2 RNA transcribed from the X chromosome. We found that in D. virilis, a species separated from melanogaster by 40 million years of evolution, all principles are active, but contribute differently to X-specificity. In melanogaster, the DCC subunit MSL2 evolved intrinsic DNA-binding selectivity for rare PionX sites, which mark the X chromosome. In virilis, PionX sites are abundant and not X-enriched. Accordingly, MSL2 lacks specific recognition. Here, roX2 RNA plays a more instructive role, counteracting a non-productive interaction of CLAMP and modulating DCC binding selectivity. Remarkably, roX2 triggers a low-diffusion chromatin binding mode characteristic of DCC. Evidently, X-specific regulation is achieved by divergent evolution of similar components.
Project description:The MLE DExH helicase and the roX lncRNAs are essential components of the chromatin modifying Dosage Compensation Complex (DCC) in Drosophila. To explore the mechanism of ribonucleoprotein complex assembly, we designed vitRIP, an unbiased, transcriptome-wide in vitro assay that reveals RNA binding specificity. We found that MLE has intrinsic specificity for U-rich sequences and tandem stem-loop structures. In vitro, the helicase binds and remodels many RNAs beyond its main target, roX2. Unwinding of roX2 by the helicase triggers their selective association with the DCC, via the MSL2 subunit. Whereas the core DCC alone does not show intrinsic RNA binding specificity, the presentation of remodeled roX2 by MLE induces a highly selective RNA binding surface in the unstructured C-terminus of MSL2. The exquisite selectivity of roX2 incorporation into the DCC thus originates from intimate cooperation between the helicase and the core DCC involving two distinct RNA selection principles and their mutual refinement.
Project description:We have studied the regulatory potential of MYST1-(MOF)-containing MSL and NSL complexes in mouse embryonic stem cells (ESCs) and neuronal progenitors. We find that both complexes influence transcription by binding to promoters as well as TSS-distal enhancer regions. In contrast to flies, the MSL complex is not enriched on the X chromosome yet it is crucial for mammalian X chromosome regulation as it specifically regulates Tsix ncRNA, the major repressor of Xist lncRNA. MSL depletion leads to severely decreased Tsix expression, reduced REX1 recruitment, and consequently accumulation of Xist RNA in ESCs. The NSL complex provides additional, Tsix-independent repression of Xist by maintaining pluripotency. MSL and NSL complexes therefore act synergistically by using distinct pathways to ensure a fail-safe mechanism for the repression of X inactivation in ESCs. We have performed ChIP-seq of KANSL3, MCRS1, MOF, MSL1 and MSL2 in mouse ESCs, and KANSL3, MOF and MSL2 in NPCs, in duplicate and normalised against their inputs. We have also performed RNA-seq following knockdown of Kansl3, Mof, Msl1 and Msl2 mouse embryonic stem cells in triplicate. NB: Kansl3 and Mof knockdown-RNAseq are analyzed against their own scrambled controls, and Msl1 and Msl2 against another scrambled control triplicate.