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Interchromatin granule clusters of the scorpionfly oocytes contain poly(A)+ RNA, heterogeneous ribonucleoproteins A/B and mRNA export factor NXF1

Authors

  • Florina M Batalova,

    Corresponding author
    1. Laboratory of Cell Morphology, Institute of Cytology RAS. Tikhoretsky Avenue 4, 194064, St. Petersburg, Russia
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  • Dmitry S Bogolyubov,

    Corresponding author
    1. Laboratory of Cell Morphology, Institute of Cytology RAS. Tikhoretsky Avenue 4, 194064, St. Petersburg, Russia
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  • Vladimir N Parfenov

    Corresponding author
    1. Institute of Cytology, Russian Academy of Sciences, 194064 St. Petersburg, Russia
    2. Laboratory of Cell Morphology, Institute of Cytology RAS. Tikhoretsky Avenue 4, 194064, St. Petersburg, Russia
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  • Part of a series marking the 70th birthday of the Cell Biology International Editor-in-Chief Denys Wheatley

Florina M. Batalova and Dmitry S. Bogolyubov contributed equally to this work.

To whom correspondence should be addressed (email vladparf@mail.cytspb.rssi.ru).

Abstract

IGCs (interchromatin granule clusters), or nuclear speckles, are one of the most universal subnuclear organelles of eukaryotic cells. We have used insect oocytes to study the possible association of poly(A)+ RNA and some factors involved in mRNA export with IGCs. Oogenesis of the mecopteran, Panorpa communis, used as a model object, is characterized by a strict cessation of oocyte genome transcription activity towards the end of oocyte growth. Our previous studies on P. communis oocyte nuclei have shown that oocyte IGC counterparts in this species are very unusual, both in morphology and molecular composition, compared with the typical IGCs of mammalian somatic cells traditionally used as a model system. We have now used microinjections of 2′-O-Me(U)22 probes conjugated with the fluorochrome TAMRA to localize poly(A)+ RNA in IGCs. RNA export proteins were also detected by immunofluorescent/confocal and immunogold labelling electron microscopy. We found that poly(A)+ RNA, hnRNPs A/B and NXF1 mRNA export factors are located in IGCs regardless of the transcriptional status of the nucleus. Our data support the idea of IGCs as universal and conserved nuclear domains that serve not only as splicing factor reservoirs, but also take part in mRNA retention and export.

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