Importin-alpha in frogs determine the size of the nucleus (Nature 2010)
NCBI Summary:
This gene encodes a member of the importin-beta family of nuclear transport proteins. The encoded protein mediates the import of specific cargo proteins from the cytoplasm to the nucleus and is dependent on the Ras-related nuclear protein-GTPase system. The encoded protein is also involved in nuclear export of the eukaryotic translation initiation factor 1A.
General function
Comment
Cellular localization
Nuclear
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Ovarian function
Oocyte maturation
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Expression regulated by
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Ovarian localization
Primordial Germ Cell, Oocyte
Comment
Stage-specific Importin13 activity influences meiosis of germ cells in the mouse. Yamaguchi YL et al. Importin-mediated transport of cargoes is known to be a key mechanism for nucleo-cytoplasmic trafficking of molecules. Ipo13, which is a member of Importin-beta gene family, encodes two transcripts by utilizing different transcription start sites. In the mouse, the full-length transcript (L-Ipo13) is expressed in the primordial germ cells in the embryo and is later expressed predominantly at the pachytene phase of meiosis in both male and female germ cells. The shorter transcript (TS-Ipo13) is only expressed in the germ cells in the adult testis. Activity of L-Ipo13, but not TS-Ipo13, mediates the nuclear accumulation of ubiquitin-conjugating enzyme 9 (UBC9), a cargo of human IPO13. This finding is consistent with the progressive accumulation of UBC9 in the nucleus of the meiotic germ cells after the onset of L-Ipo13 expression. Following siRNA knockdown of IPO13 activity in the fetal ovary, fewer germ cells are found to progress to the late-pachytene stage of meiosis and nuclear accumulation of UBC9 is reduced. Our findings strongly implicate a stage-specific role of IPO13 in nuclear-cytoplasmic translocation of cargoes that accompanies meiotic differentiation of the mouse germ cells.