A newly discovered DNA motif determined by its sequence and shape, named PionX (pioneering sites on the X), allows the dosage compensation machinery in Drosophila melanogaster to distinguish X chromosomes from autosomes. In fruitflies, the male-specific lethal dosage compensation complex (MSL-DCC) doubles gene expression from the single male X chromosome. Using an in vitro DNA immunoprecipitation assay, Villa et al. showed that MSL-DCC recognizes the X chromosome at specific sites through one of its components, MSL2. Deletion of various protein domains revealed that MSL2 interacts with DNA through two domains. A subset of genomic regions required a functional CXC domain for binding, and these sites were enriched on the X chromosome. Sequence analyses comparing CXC-dependent and -independent binding sites for MSL2 yielded two distinct motifs. Further analyses confirmed that MSL2 relies on both DNA sequence and structure to identify its binding sites.
References
Villa, R. et al. PionX sites mark the X chromosome for dosage compensation. Nature http://dx.doi.org/10.1038/nature19338 (2016)
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Koch, L. Sequence and shape help target the X chromosome. Nat Rev Genet 17, 583 (2016). https://doi.org/10.1038/nrg.2016.126
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DOI: https://doi.org/10.1038/nrg.2016.126