Recognition of 2'-O-methylated 3'-end of piRNA by the PAZ domain of a Piwi protein
Authors: Simon B, Kirkpatrick JP, Eckhardt S, Reuter M, Rocha EA, Andrade-Navarro MA, Sehr P, Pillai RS, Carlomagno T
CellNetworks People: Carlomagno Teresa
Journal: Structure. 2011 Feb 9;19(2):172-80. doi: 10.1016/j.str.2010.11.015

Piwi proteins are germline-specific Argonautes that associate with small RNAs called Piwi-interacting RNAs (piRNAs), and together with these RNAs are implicated in transposon silencing. The PAZ domain of Argonaute proteins recognizes the 3'-end of the RNA, which in the case of piRNAs is invariably modified with a 2'-O-methyl group. Here, we present the solution structure of the PAZ domain from the mouse Piwi protein, MIWI, in complex with an 8-mer piRNA mimic. The methyl group is positioned in a hydrophobic cavity made of conserved amino acids from strand β7 and helix α3, where it is contacted by the side chain of methionine-382. Our structure is similar to that of Ago-PAZ, but subtle differences illustrate how the PAZ domain has evolved to accommodate distinct 3' ends from a variety of RNA substrates.