Functional Organisation of the nucleolus and characterization of export-competent preribosomes

• Applicant: Professor Dr. Ulrich Scheer
• Subject Area: Cell Biology
• Term: from 1998 to 2007
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 5108778

We have sequenced a novel nucleolar protein from Xenopus tissue cells and oocytes (p52) which, quite surprisingly, turned out to be an ortholog of mammalian cytokeratin 19. However, the C-terminal tail domain is much shorter as compared to mammalian cytokeratin 19. We now plan to analyze the nuclear import of this protein which lacks classical nuclear localization signals. Furthermore we wish to identify topogenic sequence elements involved in nucleolar targeting and potential binding partners of p52. Since there is still no generally accepted model describing the functional organization of nucleoli, we plan to localize the rRNA genes within the nucleolar body by confocal microscopy. Recently we could visualize for the first time the three major nucleolar components by immunocytochemistry with antibodies against marker proteins and confocal microscopy. We are now in a posititon to relate the arrangement and activity of the rRNA genes (by FISH and BrUTP incorporation) to specific nucleolar compontents. Finally we plan to study the formation of nucleoli from amplified rDNA circles during early oogenesis of Xenopus with the aim to reproduce specific steps of nucleologenesis in a cell free system which is amenable to molecular analyses.

• DFG Programme: Priority Programmes
• Subproject of: SPP 1050: Funktionelle Architektur des Zellkerns
• Participating Person: Dr. Andrea Ewald