The STAR protein QKI-6 is a translational repressor.
The signal transduction and activation of RNA (STAR) family of RNA-binding proteins, whose members are evolutionarily conserved from yeast to humans, are important for a number of developmental decisions. For example, in the mouse, quaking proteins (QKI-5, QKI-6, and QKI-7) are essential for embryogenesis and myelination, whereas a closely related protein in Caenorhabditis elegans, germline defective-1 (GLD-1), is necessary for germ-line development. Recently, GLD-1 was found to be a translational repressor that acts through regulatory elements, called TGEs (for tra-2 and GLI elements), present in the 3' untranslated region of the sex-determining gene tra-2. This gene promotes female development, and repression of tra-2 translation by TGEs is necessary for the male cell fates. The finding that GLD-1 inhibits tra-2 translation raises the possibility that other STAR family members act by a similar mechanism to control gene activity. Here we demonstrate, both in vitro and in vivo, that QKI-6 functions in the same manner as GLD-1 and can specifically bind to TGEs to repress translation of reporter constructs containing TGEs. In addition, expression of QKI-6 in C. elegans wild-type hermaphrodites or in hermaphrodites that are partially masculinized by a loss-of-function mutation in the sex-determining gene tra-3 results in masculinization of somatic tissues, consistent with QKI-6 repressing the activity of tra-2. These results strongly suggest that QKI-6 may control gene activity by operating through TGEs to regulate translation. In addition, our data support the hypothesis that other STAR family members may also be TGE-dependent translational regulators.
Saccomanno
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Department of Cell Biology, Northwestern University Medical School, Chicago, IL 60611, USA.
Loushin
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C
Jan
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Punkay
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Artzt
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K
Goodwin
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EB
D020413:3' Untranslated Regions; D000818:Animals; D030801:Animals, Genetically Modified; D001483:Base Sequence; D017173:Caenorhabditis elegans / Q000166:cytology / Q000378:metabolism; D017931:DNA Primers; D005260:Female; D008297:Male; D051379:Mice; D014176:Protein Biosynthesis / Q000502:physiology*; D016601:RNA-Binding Proteins / Q000235:genetics / Q000502:physiology*; D015398:Signal Transduction / Q000502:physiology*
D020413:3' Untranslated Regions; D017931:DNA Primers; D016601:RNA-Binding Proteins