title: Global regulation of mRNA translation and stability in the early Drosophila embryo by the Smaug RNA-binding protein.
abstract: BACKGROUND
  Smaug is an RNA-binding protein that induces the degradation and represses the translation of mRNAs in the early Drosophila embryo. Smaug has two identified direct target mRNAs that it differentially regulates: nanos and Hsp83. Smaug represses the translation of nanos mRNA but has only a modest effect on its stability, whereas it destabilizes Hsp83 mRNA but has no detectable effect on Hsp83 translation. Smaug is required to destabilize more than one thousand mRNAs in the early embryo, but whether these transcripts represent direct targets of Smaug is unclear and the extent of Smaug-mediated translational repression is unknown.
  
  
  RESULTS
  To gain a panoramic view of Smaug function in the early embryo, we identified mRNAs that are bound to Smaug using RNA co-immunoprecipitation followed by hybridization to DNA microarrays. We also identified mRNAs that are translationally repressed by Smaug using polysome gradients and microarrays. Comparison of the bound mRNAs to those that are translationally repressed by Smaug and those that require Smaug for their degradation suggests that a large fraction of Smaug's target mRNAs are both translationally repressed and degraded by Smaug. Smaug directly regulates components of the TRiC/CCT chaperonin, the proteasome regulatory particle and lipid droplets, as well as many metabolic enzymes, including several glycolytic enzymes.
  
  
  CONCLUSIONS
  Smaug plays a direct and global role in regulating the translation and stability of a large fraction of the mRNAs in the early Drosophila embryo, and has unanticipated functions in control of protein folding and degradation, lipid droplet function and metabolism.
authors.forename: Linan
authors.initials: L
authors.lastname: Chen
authors.forename: Jason G
authors.initials: JG
authors.lastname: Dumelie
authors.forename: Xiao
authors.initials: X
authors.lastname: Li
authors.forename: Matthew Hk
authors.initials: MH
authors.lastname: Cheng
authors.forename: Zhiyong
authors.initials: Z
authors.lastname: Yang
authors.forename: John D
authors.initials: JD
authors.lastname: Laver
authors.forename: Najeeb U
authors.initials: NU
authors.lastname: Siddiqui
authors.forename: J Timothy
authors.initials: JT
authors.lastname: Westwood
authors.forename: Quaid
authors.initials: Q
authors.lastname: Morris
authors.forename: Howard D
authors.initials: HD
authors.lastname: Lipshitz
authors.forename: Craig A
authors.initials: CA
authors.lastname: Smibert
mesh_terms: D000483:Alleles; D000818:Animals; D004330:Drosophila / Q000196:embryology / Q000235:genetics*; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism*; D004625:Embryo, Nonmammalian / Q000378:metabolism; D044127:Epigenesis, Genetic; D005260:Female; D018507:Gene Expression Regulation, Developmental; D006360:Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism; D047468:Immunoprecipitation; D012333:RNA, Messenger / Q000235:genetics* / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D029721:Drosophila Proteins; D006360:Heat-Shock Proteins; C089272:Hsp83 protein, Drosophila; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D012097:Repressor Proteins; C402587:smg protein, Drosophila; C070574:nos protein, Drosophila