Structural highlights
Function[EXU_DROME] Ensures the proper localization of the mRNA of the bicoid gene to the anterior regions of the oocyte thus playing a fundamental role in the establishment of the polarity of the oocyte. May bind the bcd mRNA. Publication Abstract from PubMedAnterior patterning in Drosophila is mediated by the localization of bicoid (bcd) mRNA at the anterior pole of the oocyte. Exuperantia (Exu) is a putative exonuclease (EXO) associated with bcd and required for its localization. We present the crystal structure of Exu, which reveals a dimeric assembly with each monomer consisting of a 3'-5' EXO-like domain and a sterile alpha motif (SAM)-like domain. The catalytic site is degenerate and inactive. Instead, the EXO-like domain mediates dimerization and RNA binding. We show that Exu binds RNA directly in vitro, that the SAM-like domain is required for RNA binding activity and that Exu binds a structured element present in the bcd 3' untranslated region with high affinity. Through structure-guided mutagenesis, we show that Exu dimerization is essential for bcd localization. Our data demonstrate that Exu is a noncanonical RNA-binding protein with EXO-SAM-like domain architecture that interacts with its target RNA as a homodimer. The bicoid mRNA localization factor Exuperantia is an RNA-binding pseudonuclease.,Lazzaretti D, Veith K, Kramer K, Basquin C, Urlaub H, Irion U, Bono F Nat Struct Mol Biol. 2016 Jul 4. doi: 10.1038/nsmb.3254. PMID:27376588[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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