The Nanos gradient in Drosophila embryos is generated by translational regulation.
Abdominal segmentation in the Drosophila embryo is governed by a gradient of Nanos (Nos) emanating from the posterior pole. This gradient is derived from translation of the nos mRNA that is localized in the pole plasm; in contrast, unlocalized nos mRNA is translationally repressed. Here we define the essential signals in the 3' untranslated region (UTR) of nos mRNA. Deletion of a 184-nucleotide translational control element (TCE) from the 3' UTR leads to the derepression of nos mRNA in the bulk cytoplasm and the development of lethal anterior defects. Furthermore, a minimal mRNA containing essentially only the TCE in its 3' UTR rescues nos- embryos to adulthood. The TCE is also sufficient to confer on maternal torso mRNA all three aspects of nos mRNA regulation: translational repression in the bulk cytoplasm, localization to the pole plasm, and translational activation at the posterior pole. These three phenomena are coupled intimately, as mutations in a pair of CUGGC pentamers within the TCE simultaneously abrogate all three regulatory events. This coupling suggests a model in which the polarized distribution of nos protein is generated primarily by translational control and that nos mRNA localization is a byproduct of this regulation, at least in part.
Department of Genetics, Howard Hughes Medical Institute, Duke University Medical Center, Durham, North Carolina 27710, USA.
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Dahanukar
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Wharton
D000818:Animals; D030801:Animals, Genetically Modified; D001483:Base Sequence; D004330:Drosophila / Q000196:embryology / Q000235:genetics* / Q000378:metabolism; D029721:Drosophila Proteins; D005786:Gene Expression Regulation; D007301:Insect Hormones / Q000235:genetics*; D008969:Molecular Sequence Data; D014176:Protein Biosynthesis; D011506:Proteins / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D011817:Rabbits; D020794:Receptor Protein-Tyrosine Kinases / Q000235:genetics; D012045:Regulatory Sequences, Nucleic Acid; D012091:Repetitive Sequences, Nucleic Acid; D017384:Sequence Deletion
D029721:Drosophila Proteins; D007301:Insect Hormones; D011506:Proteins; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; C091675:osk protein, Drosophila; C070574:nos protein, Drosophila; D020794:Receptor Protein-Tyrosine Kinases; C080148:tor protein, Drosophila