Dataset Information

Divergent evolutionary strategies for selective sex chromosome regulation in Drosophila

ABSTRACT: 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.

INSTRUMENT(S): Q Exactive HF

ORGANISM(S): Drosophila Virilis

SUBMITTER: Ignasi Forne

LAB HEAD: Prof Peter B. Becker

PROVIDER: PXD023747 | Pride | 2021-06-23

REPOSITORIES: Pride

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Publications

Divergent evolution toward sex chromosome-specific gene regulation in Drosophila.

Villa Raffaella R Jagtap Pravin Kumar Ankush PKA Thomae Andreas W AW Campos Sparr Aline A Forné Ignasi I Hennig Janosch J Straub Tobias T Becker Peter B PB

Genes & development 20210617 13-14

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 noncoding 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 a ...[more]

PMID: 34140353

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Project description:Here we exploit the essential process of X-chromosome dosage compensation to elucidate basic mechanisms that control the assembly, genome-wide binding, and function of gene regulatory complexes that act over large chromosomal territories. We demonstrate that a subunit of C. elegans MLL/COMPASS, a gene-activation complex, acts within the dosage compensation complex (DCC), a condensin complex, to target the DCC to both X chromosomes of hermaphrodites and thereby reduce chromosome-wide gene expression. The DCC binds to two categories of sites on X: rex sites that recruit the DCC in an autonomous, sequence- dependent manner, and dox sites that reside primarily in promoters of expressed genes and bind the DCC robustly only when attached to X. We find that DCC mutants that abolish rex-site binding do not eliminate dox-site binding, but instead reduce it to the level observed at autosomal binding sites in wild-type animals. Changes in DCC binding to these non-rex sites occur throughout development and correlate with transcriptional activity of adjacent genes. Moreover, autosomal DCC binding is enhanced by rex-site binding in cis in X-autosome fusion chromosomes. Thus, dox and autosomal sites exhibit similar binding properties. Our data support a model for DCC binding in which low-level DCC binding at dox and autosomal sites is dictated by intrinsic properties correlated with high transcriptional activity. Sex-specific DCC recruitment to rex sites then greatly elevates DCC binding to dox sites in cis, which lack intrinsically high DCC affinity on their own. We also show here that the C. elegans DCC achieves dosage compensation through its effects on transcription. ChIP-chip experiments using antibodies against DPY-27, SDC-3, DPY-30, DPY-26, MIX-1, SMC-4, ASH-2 in wild-type embryos. ChIP-chip experiments using antibodies against SDC-3, DPY-27, DPY-30, ASH-2, and IgG in different DCC mutants. ChIP-chip experiments using antibodies against RNA Pol II (hypophosphorylated and S2 and S5) in wild type and sdc-2 partial loss of function mutants.

Dataset Information

Divergent evolutionary strategies for selective sex chromosome regulation in Drosophila

Publications

Divergent evolution toward sex chromosome-specific gene regulation in <i>Drosophila</i>.

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