Vertebrate Spt2 is a novel nucleolar histone chaperone that assists in ribosomal DNA transcription
Vertebrate Spt2 is a novel nucleolar histone chaperone that assists in ribosomal DNA transcription
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DOI：
10.1242/jcs.112623
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发表时间：
2013-03-15
影响因子：
4
通讯作者：
Kurumizaka, Hitoshi
中科院分区：
文献类型：
--
作者：
Osakabe, Akihisa;Tachiwana, Hiroaki;Kurumizaka, Hitoshi
在真核生物中，转录在组蛋白结合蛋白（如染色质/核小体重塑因子和组蛋白伴侣）的协助下在染色质背景下发生。然而，目前还不清楚每个重塑因子或组蛋白伴侣在转录中的功能。在这里，我们确定了一种新的组蛋白结合蛋白，Spt 2，在高等真核生物。重组人Spt 2与组蛋白和DNA结合，并在体外促进核小体组装。Spt 2在鸡DT 40细胞中积累在核仁中并与RNA聚合酶I相互作用，表明其参与核糖体RNA转录。一致地，Spt 2缺陷型鸡DT 40细胞对RNA聚合酶I抑制剂敏感，并表现出转录活性降低，如转录连续测定所示。Spt 2的结构域分析表明，C-末端区域，包含与酵母Spt 2同源的区域，负责组蛋白结合，而中心区域是必需的核仁定位和DNA结合。基于这些结果，我们得出结论，脊椎动物Spt 2是一种新的组蛋白伴侣与一个单独的DNA结合结构域，有利于核糖体DNA转录过程中通过染色质重塑。
In eukaryotes, transcription occurs in the chromatin context with the assistance of histone-binding proteins, such as chromatin/nucleosome remodeling factors and histone chaperones. However, it is unclear how each remodeling factor or histone chaperone functions in transcription. Here, we identify a novel histone-binding protein, Spt2, in higher eukaryotes. Recombinant human Spt2 binds to histones and DNA, and promotes nucleosome assembly in vitro. Spt2 accumulates in nucleoli and interacts with RNA polymerase I in chicken DT40 cells, suggesting its involvement in ribosomal RNA transcription. Consistently, Spt2-deficient chicken DT40 cells are sensitive to RNA polymerase I inhibitors and exhibit decreased transcription activity, as shown by a transcription run-on assay. Domain analyses of Spt2 revealed that the C-terminal region, containing the region homologous to yeast Spt2, is responsible for histone binding, while the central region is essential for nucleolar localization and DNA binding. Based on these results, we conclude that vertebrate Spt2 is a novel histone chaperone with a separate DNA-binding domain that facilitates ribosomal DNA transcription through chromatin remodeling during transcription.