Crystal Structure and Activity of the Endoribonuclease Domain of the piRNA Pathway Factor Maelstrom
Crystal Structure and Activity of the Endoribonuclease Domain of the piRNA Pathway Factor Maelstrom
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DOI：
10.1016/j.celrep.2015.03.030
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发表时间：
2015-04-21
期刊：
影响因子：
8.8
通讯作者：
Nureki, Osamu
中科院分区：
文献类型：
--
作者：
Matsumoto, Naoki;Sato, Kaoru;Nureki, Osamu
PIWI相互作用RNA（piRNA）保护基因组免受动物性腺中转座子的影响。Maelstrom（Mael）是一种进化上保守的蛋白质，由高迁移率族（HMG）结构域和MAEL结构域组成，并且对于各种物种（如果蝇和小鼠）中的piRNA介导的转录转座子沉默是必需的。然而，它的结构和生物化学功能仍然难以捉摸。在这里，我们报告的晶体结构的MAEL域从果蝇Mael，在1.6埃的分辨率。该结构揭示了MAEL结构域具有RNA酶H样折叠，但缺乏RNA酶H样超家族核酸酶中保守的典型催化残基。我们的生化分析表明，MAEL结构域具有单链RNA（ssRNA）特异性内切酶活性。我们基于细胞的分析进一步表明，ssRNA切割活性似乎与果蝇中piRNA介导的转录转座子沉默无关。我们的发现为理解Mael在皮尔纳通路中的多种作用提供了线索。
PIWI-interacting RNAs (piRNAs) protect the genome from transposons in animal gonads. Maelstrom (Mael) is an evolutionarily conserved protein, composed of a high-mobility group (HMG) domain and a MAEL domain, and is essential for piRNA-mediated transcriptional transposon silencing in various species, such as Drosophila and mice. However, its structure and biochemical function have remained elusive. Here, we report the crystal structure of the MAEL domain from Drosophila melanogaster Mael, at 1.6 angstrom resolution. The structure reveals that the MAEL domain has an RNase H-like fold but lacks canonical catalytic residues conserved among RNase H-like superfamily nucleases. Our biochemical analyses reveal that the MAEL domain exhibits single-stranded RNA (ssRNA)-specific endonuclease activity. Our cell-based analyses further indicate that ssRNA cleavage activity appears dispensable for piRNA-mediated transcriptional transposon silencing in Drosophila. Our findings provide clues toward understanding the multiple roles of Mael in the piRNA pathway.