4p1z
From Proteopedia
Structure of the MID domain from MIWI
Structural highlights
Function[PIWL1_MOUSE] Plays a central role during spermatogenesis by repressing transposable elements and preventing their mobilization, which is essential for the germline integrity. Acts 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 methylation and subsequent repression of transposons. Directly binds methylated piRNAs, a class of 24 to 30 nucleotide RNAs that are generated by a Dicer-independent mechanism and are primarily derived from transposons and other repeated sequence elements. Besides their function in transposable elements repression, piRNAs are probably involved in other processes during meiosis such as translation regulation. Probable component of some RISC complex, which mediates RNA cleavage and translational silencing. Also plays a role in the formation of chromatoid bodies and is required for some miRNAs stability.[1] Publication Abstract from PubMedPiwi-interacting RNAs (piRNAs) guide Piwi Argonautes to suppress transposon activity in animal gonads. Known piRNA populations are extremely complex, with millions of individual sequences present in a single organism. Despite this complexity, specific Piwi proteins incorporate piRNAs with distinct nucleotide- and transposon strand-biases (antisense or sense) of unknown origin. Here, we examined the contribution of structural domains in Piwi proteins toward defining these biases. We report the first crystal structure of the MID domain from a Piwi Argonaute and use docking experiments to show its ability to specify recognition of 5' uridine (1U-bias) of piRNAs. Mutational analyses reveal the importance of 5' end-recognition within the MID domain for piRNA biogenesis in vivo. Finally, domain-swapping experiments uncover an unexpected role for the MID-PIWI module of a Piwi protein in dictating the transposon strand-orientation of its bound piRNAs. Our work identifies structural features that allow distinguishing individual Piwi members during piRNA biogenesis. The MID-PIWI module of Piwi proteins specifies nucleotide- and strand-biases of piRNAs.,Cora E, Pandey RR, Xiol J, Taylor J, Sachidanandam R, McCarthy AA, Pillai RS RNA. 2014 Apr 22. PMID:24757166[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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