Specific cooperation between imp-α2 and imp-β/ketel in spindle assembly during drosophila early nuclear divisions

Erika Virágh, Mátyás Gorjánácz, István Török, Tolga Eichhorn, Sowjanya Kallakuri, Tamás Szlanka, István Kiss, Bernard M. Mechler

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2 Citations (Scopus)

Abstract

The multifunctional factors Imp-α and Imp-β are involved in nuclear protein import, mitotic spindle dynamics, and nuclear membrane formation. Further more, each of the three members of the Imp-α family exerts distinct tasks during development. In Drosophila melanogaster, the imp-α2gene is critical during oogenesis for ring canal assembly; specific mutations, which allow oogenesis to proceed normally,were found to block early embryonic mitosis. Here, we show that imp-α2 and imp-β genetically interact during early embryonic development, and we characterize the pattern of defects affecting mitosis in embryos laid by heterozygous imp-α2D14 and impβKetRE34 females. Embryonic development is arrested in these embryos but is unaffected in combinations between imp-βKetRE34 and null mutations in imp-α1 or imp-α3. Furthermore, the imp-α2D14/imp-βKetRE34 interaction could only be rescued by an imp-α2 transgene, albeit not imp-α1 or imp-α3, showing the exclusive imp-α2 function with imp-β.Use of transgenes carrying modifications in the major Imp-α2domains showed the critical requirement of the nuclear localization signal binding (NLSB) site in this process. In the mutant embryos,we found metaphase-arrested mitoses made of enlarged spindles, suggesting an unrestrained activity of factors promoting spindle assembly. In accordance with this, we found that Imp-βKetRE34 and Imp-βKetD bind a high level of RanGTP/GDP, and a deletion decreasing RanGTP level suppresses the imp-βKetRE34 phenotype. These data suggest that a fine balance among Imp-α2, Imp-β,RanGTP, and theNLS cargos is critical for mitoticprogression during early embryonic development.

Original languageEnglish
Pages (from-to)1-14
Number of pages14
JournalG3: Genes, Genomes, Genetics
Volume2
Issue number1
DOIs
Publication statusPublished - Jan 1 2012

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Keywords

  • Drosophila
  • Genetic interaction
  • Importins
  • Mitosis
  • Spindle formation

ASJC Scopus subject areas

  • Molecular Biology
  • Genetics
  • Genetics(clinical)

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