4ybg
From Proteopedia
Crystal structure of the MAEL domain of Drosophila melanogaster Maelstrom
Structural highlights
Function[MAEL_DROME] Involved both in the piRNA and miRNA metabolic processes. As a component of the meiotic nuage, plays a central role during oogenesis by repressing transposable elements and preventing their mobilization, which is essential for the germline integrity. Repression of transposable elements is mediated via the piRNA metabolic process, which mediates the repression of transposable elements during meiosis by forming complexes composed of piRNAs and Piwi proteins and governs the repression of transposons. As a nuclear component, it is required for proper differentiation in the germline stem cell (GSC) lineage by repressing microRNA-7 (miR-7), thereby acting as an indirect regulator of bag-of-marbles (Bam). Acts by binding to the promoter of miR-7 gene and repressing its expression; miR-7 repression alleviates the Bam repression by miR-7, thereby allowing differentiation in the germline stem cell (GSC) lineage. Indirectly required to position the microtubule organizing center in stage 2-6 oocytes.[1] [2] [3] [4] [5] Publication Abstract from PubMedPIWI-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 A 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. Crystal Structure and Activity of the Endoribonuclease Domain of the piRNA Pathway Factor Maelstrom.,Matsumoto N, Sato K, Nishimasu H, Namba Y, Miyakubi K, Dohmae N, Ishitani R, Siomi H, Siomi MC, Nureki O Cell Rep. 2015 Apr 21;11(3):366-75. doi: 10.1016/j.celrep.2015.03.030. Epub 2015 , Apr 9. PMID:25865890[6] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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