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首页> 外文期刊>Chromosoma >Dosage compensation and intercalary heterochromatin in X chromosomes of Drosophila melanogaster
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Dosage compensation and intercalary heterochromatin in X chromosomes of Drosophila melanogaster

机译：果蝇X染色体的剂量补偿和插层异染色质

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摘要

Regions of intercalary heterochromatin (IH) are dispersed in the euchromatic arms of polytene chromosomes and share the main properties of heterochromatin, namely chromosome constrictions resulting from DNA underreplication. These constrictions are frequent on the paired X chromosomes of females, but are practically absent from the single X chromosome of males. These sex-specific differences have been proposed to reflect the different levels of transcription and chromosome compaction due to dosage compensation, which in turn may affect the degree of underreplication in IH regions. To test this hypothesis, we induced dosage compensation in females by ectopic expression of MSL-2 protein. We then measured the extent of underreplication in IH regions by determining frequencies of constrictions, or by Southern blot analysis using a fragment of the ten a gene which is located in IH region 11A6–9. Females transheterozygous for Sxl fhv1 /Sxl f1 or carrying a constitutive msl-2 transgene are known to hypertranscribe their X chromosomes. In such females, both the frequency of constrictions and DNA underreplication were reduced. Suppression of underreplication occurs only when a complete functional MSL complex assembles on the X chromosomes. We also used three strains that carried constitutive transgenes of msl-2 with mutations in the 5′ untranslated regions. These strains produced normal levels of SXL protein, but variable levels of MSL-2 protein. The SXL protein did not prevent the formation of an MSL complex in these transgenic females. We found that the extent of underreplication of ten a DNA in IH region 11A6–9 negatively correlates with the amount of MSL complex.
机译：插层异染色质（IH）区域分散在多染色体的常染色体臂中，并具有异染色质的主要特性，即DNA欠复制导致的染色体收缩。这些收缩在雌性的成对的X染色体上很常见，但实际上在雄性的单个X染色体上却不存在。已经提出这些性别特异性差异以反映由于剂量补偿引起的转录和染色体紧缩的不同水平，这又可能影响IH区的复制不足程度。为了验证该假设，我们通过异位表达MSL-2蛋白诱导了女性的剂量补偿。然后，我们通过确定收缩的频率或使用位于IH区11A6–9中的10个基因的片段进行Southern blot分析来测量IH区的复制不足程度。 Sxl fhv1 / Sxl f1 或携带组成型msl-2转基因的雌性杂合子已知会超转录其X染色体。在这样的雌性中，收缩的频率和DNA复制不足均降低了。仅当在X染色体上装配了完整的功能性MSL复合体时，才发生复制不足的抑制。我们还使用了三株携带msl-2组成型转基因并在5'非翻译区发生突变的菌株。这些菌株产生正常水平的SXL蛋白，但产生可变水平的MSL-2蛋白。在这些转基因雌性中，SXL蛋白不能阻止MSL复合物的形成。我们发现IH区域11A6–9中10 a DNA的复制不足程度与MSL复合物的数量负相关。

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  • 来源
    《Chromosoma》 |2002年第2期|106-113|共8页
  • 作者

    Artyom A. Alekseyenko; Olga V. Demakova; Elena S. Belyaeva; Grigorii F. Makarevich; Irina V. Kotlikova; Rolf Nöthiger; Igor F. Zhimulev;

  • 作者单位

    Institute of Cytology and Genetics Siberian Division of Russian Academy of Sciences Koptyuga Avenue 2 Novosibirsk 630090 Russia;

    Institute of Cytology and Genetics Siberian Division of Russian Academy of Sciences Koptyuga Avenue 2 Novosibirsk 630090 Russia;

    Institute of Cytology and Genetics Siberian Division of Russian Academy of Sciences Koptyuga Avenue 2 Novosibirsk 630090 Russia;

    Department of Cytology and Genetics Novosibirsk State University Novosibirsk 630090 Russia;

    Department of Cytology and Genetics Novosibirsk State University Novosibirsk 630090 Russia;

    Zoological Institute University of Zurich 8057 Zurich Switzerland;

    Institute of Cytology and Genetics Siberian Division of Russian Academy of Sciences Koptyuga Avenue 2 Novosibirsk 630090 Russia;

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