POLYADENYLATED RNA AND MRNA EXPORT FACTORS IN EXTRACHROMOSOMAL NUCLEAR DOMAINS OF VITELLOGENIC OOCYTES OF THE INSECT,
TENEBRIO MOLITOR
D.S. Bogolyubov,1 A.M. Kiselyov, S.V. Shabelnikov, V.N. Parfenov
Institute of Cytology of the RAS, St.Petersburg;
1 e-mail: dmitr@mail.cytspb.rssi.ru
The nucleus of vitellogenic oocytes of the yellow mealworm, Tenebrio molitor, contains a karyosphere that consists of the condensed chromatin embedded in an
extrachromosomal fibrogranular material. Numerous nuclear bodies located freely in the nucleoplasm are also observed. Amongst these bodies, counterparts of nuclear speckles
(= interchromatin granule clusters, IGCs) can be identified by the presence of the marker protein SC35. Microinjections of fluorescently tagged methyloligoribonucleotide probes
2'-Î-Me(U)22, complementary to poly(A) tails of RNAs, revealed poly(A)+ RNA in the vast majority of IGCs. We found that all
T. molitor oocyte IGCs contain heterogeneous ribonucleoprotein (hnRNP) core protein A1 that localizes to IGCs in an RNA-dependent manner. The extrachromosomal material
of the karyosphere and a part of nucleoplasmic IGCs also contain the adapter protein A1 that is known to provide a link between pre-mRNA splicing and mRNA export. The essential
mRNA export factor/receptor NXF1 was observed to colocalize with Aly. In nucleoplasmic IGCs, NXF1 was found to localize in an RNA-dependent manner whereas it is
RNA-independently located in the extrachromosomal material of the karyosphere. We believe our data suggest on a role of the nucleoplasmic IGCs in mRNA biogenesis and retention
in a road to nuclear export.
Key words: Tenebrio molitor, oocyte nucleus, nuclear bodies, interchromatin granule clusters, laser scanning confocal microscopy
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