Visualisation of Ribosomal Subunits Interaction in Drosophila Cells. Akilu S. Abdullahi. Bioscience, University of Birmingham, Birmingham, Birmingham, W. Midlands, United Kingdom.

   Abstract The nuclear membrane is a unique feature of eukaryotes. It divides the cell into two main compartments: nucleus and cytoplasm. Specific steps of the gene expression are restricted either to the nucleus or the cytoplasm. Transcription and RNA processing takes place in the nucleus, but translation is restricted to only the cytoplasm. It was therefore believed that there was no direct link between nuclear events such as pre-mRNA splicing and cytoplasmic events such as translation and mRNA degradation. This view has been challenged in recent years by reports that indicate that the nature of the nuclear mRNP also impinges on the cytoplasmic events such as translation and NMD. This research is aimed at further addressing the issue whether ribosomal subunits interact in the nucleus and whether the interaction is translation dependent. Visualization of ribosomal interactions in drosophila cells was carried out based on bimolecular fluorescence complementation technique (BiFC). To visualize association between ribosomal subunits, I have tagged pairs of Drosophila ribosomal proteins (RPs) located in different subunits with mutually complementing halves of Venus fluorescent protein or YFP. Pairs of tagged RPs expected to interact, or be adjacent in the 80S structure, showed strong BiFC fluorescence, but pairs far apart did not. The results obtained showed that translation sites are more apparent in the cytoplasm. However, some percentage of the cells showed a signal in the nucleolus. This signal was found to be enhanced by translation elongation inhibitors and the proportion of cells with nucleolar signal increased. Notably, the nucleolar signal observed was prevented by Pol II inhibition. This technique achieved 80S visualization in both cultured cells and in fly tissues in vivo.