The Drosophila Y chromosome is gene poor and mainly consists of silenced, repetitive DNA. Nonetheless, the Y influences expression of hundreds of genes genome-wide, possibly by sequestering key components of the heterochromatin machinery away from other positions in the genome. To test the influence of the Y chromosome on the genome-wide chromatin landscape, we assayed the genomic distribution of histone modifications associated with gene activation (H3K4me3) or heterochromatin (H3K9me2 and H3K9me3) in fruit flies with varying sex chromosome complements (X0, XY, and XYY males; XX and XXY females). Consistent with the general deficiency of active chromatin modifications on the Y, we find that Y gene dose has little influence on the genomic distribution of H3K4me3. In contrast, both the presence and the number of Y chromosomes strongly influence genome-wide enrichment patterns of repressive chromatin modifications. Highly repetitive regions such as the pericentromeres, the dot, and the Y chromosome (if present) are enriched for heterochromatic modifications in wildtype males and females, and even more strongly in X0 flies. In contrast, the additional Y chromosome in XYY males and XXY females diminishes the heterochromatic signal in these normally silenced, repeat-rich regions, which is accompanied by an increase in expression of Y-linked repeats. We find hundreds of genes that are expressed differentially between individuals with aberrant sex chromosome karyotypes, many of which also show sex-biased expression in wildtype Drosophila. Thus, Y chromosomes influence heterochromatin integrity genome-wide, and differences in the chromatin landscape of males and females may also contribute to sex-biased gene expression and sexual dimorphisms.

中文翻译：

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果蝇Y染色体影响全基因组的异染色质完整性。

果蝇Y染色体缺乏基因，主要由沉默的重复DNA组成。尽管如此，Y可能会通过将异染色质机制的关键成分与基因组中的其他位置隔离，影响整个基因组中数百个基因的表达。为了测试Y染色体对全基因组染色质景观的影响，我们分析了具有不同性别染色体互补性（X0，XY）的果蝇中与基因激活（H3K4me3）或异染色质（H3K9me2和H3K9me3）相关的组蛋白修饰的基因组分布，以及XYY男性； XX和XXY女性）。与Y上活性染色质修饰的一般缺陷一致，我们发现Y基因剂量对H3K4me3的基因组分布影响很小。相反，Y染色体的存在和数量都强烈影响阻抑染色质修饰的全基因组富集模式。高度重复的区域（如着丝粒，点和Y染色体）（如果存在）在野生型雄性和雌性中富集，用于异色修饰，在X0蝇中则更强。相反，在XYY雄性和XXY雌性中额外的Y染色体减少了这些通常沉默的，重复序列丰富的区域中的异色信号，并伴随着Y连接重复序列的表达增加。我们发现数百个在异常性染色体核型个体之间差异表达的基因，其中许多在果蝇果蝇中也表现出性别偏向性表达。因此，Y染色体会影响整个基因组的异染色质完整性，