X-chromosome dosage compensation by the MSL (male-specific lethal) complex is required in Drosophila melanogaster to increase gene expression from the single male X to equal that of both female X chromosomes. Instead of focusing solely on protein complexes released from DNA, here we used chromatin-interacting protein MS (ChIP-MS) to identify MSL interactions on cross-linked chromatin. We identified MSL-enriched histone modifications, including histone H4 Lys16 acetylation and histone H3 Lys36 methylation, and CG4747, a putative Lys36-trimethylated histone H3 (H3K36me3)-binding protein. CG4747 is associated with the bodies of active genes, coincident with H3K36me3, and is mislocalized in the Set2 mutant lacking H3K36me3. CG4747 loss of function in vivo results in partial mislocalization of the MSL complex to autosomes, and RNA interference experiments confirm that CG4747 and Set2 function together to facilitate targeting of the MSL complex to active genes, validating the ChIP-MS approach.

中文翻译：

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ChIP 质谱法捕获的染色质蛋白与果蝇的剂量补偿有关。

黑腹果蝇需要通过 MSL（雄性特异性致死）复合物进行 X 染色体剂量补偿，以将单个雄性 X 的基因表达增加到与两条雌性 X 染色体相等的基因表达。在这里，我们不是只关注从 DNA 释放的蛋白质复合物，而是使用染色质相互作用蛋白 MS (ChIP-MS) 来识别交联染色质上的 MSL 相互作用。我们鉴定了富含 MSL 的组蛋白修饰，包括组蛋白 H4 Lys16 乙酰化和组蛋白 H3 Lys36 甲基化，以及 CG4747，一种推定的 Lys36 三甲基化组蛋白 H3 (H3K36me3) 结合蛋白。CG4747 与活性基因体相关，与 H3K36me3 一致，并且在缺少 H3K36me3 的 Set2 突变体中错误定位。CG4747 体内功能丧失导致 MSL 复合物部分错误定位到常染色体，