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J Cell Sci. 2012 Mar 15;125(Pt 6):1407-19. doi: 10.1242/jcs.090381. Epub 2012 Feb 10.

Modulation of gurken translation by insulin and TOR signaling in Drosophila.

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  • 1Department of Biology SUNY Fredonia, Fredonia, NY 14063, USA. scott.ferguson@fredonia.edu

Abstract

Localized Gurken (Grk) translation specifies the anterior-posterior and dorsal-ventral axes of the developing Drosophila oocyte; spindle-class females lay ventralized eggs resulting from inefficient grk translation. This phenotype is thought to result from inhibition of the Vasa RNA helicase. In a screen for modifiers of the eggshell phenotype in spn-B flies, we identified a mutation in the lnk gene. We show that lnk mutations restore Grk expression but do not suppress the persistence of double-strand breaks nor other spn-B phenotypes. This suppression does not affect Egfr directly, but rather overcomes the translational block of grk messages seen in spindle mutants. Lnk was recently identified as a component of the insulin/insulin-like growth factor signaling (IIS) and TOR pathway. Interestingly, direct inhibition of TOR with rapamycin in spn-B or vas mutant mothers can also suppress the ventralized eggshell phenotype. When dietary protein is inadequate, reduced IIS-TOR activity inhibits cap-dependent translation by promoting the activity of the translation inhibitor eIF4E-binding protein (4EBP). We hypothesize that reduced TOR activity promotes grk translation independent of the canonical Vasa- and cap-dependent mechanism. This model might explain how flies can maintain the translation of developmentally important transcripts during periods of nutrient limitation when bulk cap-dependent translation is repressed.

PMID:
22328499
[PubMed - indexed for MEDLINE]
PMCID:
PMC3336377
Free PMC Article

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