Cell Reports
Volume 12, Issue 4, 28 July 2015, Pages 587-598
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Article
The Crystal Structure of the Drosophila Germline Inducer Oskar Identifies Two Domains with Distinct Vasa Helicase- and RNA-Binding Activities

https://doi.org/10.1016/j.celrep.2015.06.055Get rights and content
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Highlights

  • Oskar protein interacts physically with nos, pgc, and gcl mRNAs in vivo

  • Crystal structures of the previously uncharacterized domains of Oskar were solved

  • The OSK domain is an RNA-binding domain related to SGNH hydrolases

  • The LOTUS domain forms dimers and interacts with the RNA helicase Vasa in vitro

Summary

In many animals, the germ plasm segregates germline from soma during early development. Oskar protein is known for its ability to induce germ plasm formation and germ cells in Drosophila. However, the molecular basis of germ plasm formation remains unclear. Here, we show that Oskar is an RNA-binding protein in vivo, crosslinking to nanos, polar granule component, and germ cell-less mRNAs, each of which has a role in germline formation. Furthermore, we present high-resolution crystal structures of the two Oskar domains. RNA-binding maps in vitro to the C-terminal domain, which shows structural similarity to SGNH hydrolases. The highly conserved N-terminal LOTUS domain forms dimers and mediates Oskar interaction with the germline-specific RNA helicase Vasa in vitro. Our findings suggest a dual function of Oskar in RNA and Vasa binding, providing molecular clues to its germ plasm function.

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This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).