Nucleation, propagation and cleavage of target RNAs in Ago silencing complexes

Article

关键词: CRYSTAL-STRUCTURE;    STRUCTURAL BASIS;    RECOGNITION;    ARGONAUTE;    DNA;    MESSENGER;    RISC;    MECHANISMS;    SLICER;    INTERFERENCE;   

DOI  :  10.1038/nature08434

来源: SCIE

【 摘 要 】

The slicer activity of the RNA-induced silencing complex resides within its Argonaute (Ago) component, in which the PIWI domain provides the catalytic residues governing guide-strand mediated site-specific cleavage of target RNA. Here we report on structures of ternary complexes of Thermus thermophilus Ago catalytic mutants with 5'-phosphorylated 21-nucleotide guide DNA and complementary target RNAs of 12, 15 and 19 nucleotides in length, which define the molecular basis for Mg2+-facilitated site-specific cleavage of the target. We observe pivot-like domain movements within the Ago scaffold on proceeding from nucleation to propagation steps of guide-target duplex formation, with duplex zippering beyond one turn of the helix requiring the release of the 3'-end of the guide from the PAZ pocket. Cleavage assays on targets of various lengths supported this model, and sugar-phosphate-backbone-modified target strands showed the importance of structural and catalytic divalent metal ions observed in the crystal structures.

【 授权许可】

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