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Nat Commun. 2015 Apr 8;6:6643. doi: 10.1038/ncomms7643.

Rio1 promotes rDNA stability and downregulates RNA polymerase I to ensure rDNA segregation.

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Department of Experimental Oncology, European Institute of Oncology, via Adamello 16, Milan 20139, Italy.
1] The Research Institute of Molecular Pathology, Dr Bohr-Gasse 7, Vienna 1030, Austria [2] The IMBA Institute of Molecular Biotechnology of the Austrian Academy of Sciences, Dr Bohr-Gasse 3, Vienna 1030, Austria.
Lehrstuhl für Biochemie III, Universität Regensburg, Universitätsstraβe 31, 93053 Regensburg, Germany.


The conserved protein kinase Rio1 localizes to the cytoplasm and nucleus of eukaryotic cells. While the roles of Rio1 in the cytoplasm are well characterized, its nuclear function remains unknown. Here we show that nuclear Rio1 promotes rDNA array stability and segregation in Saccharomyces cerevisiae. During rDNA replication in S phase, Rio1 downregulates RNA polymerase I (PolI) and recruits the histone deacetylase Sir2. Both interventions ensure rDNA copy-number homeostasis and prevent the formation of extrachromosomal rDNA circles, which are linked to accelerated ageing in yeast. During anaphase, Rio1 downregulates PolI by targeting its subunit Rpa43, causing PolI to dissociate from the rDNA. By stimulating the processing of PolI-generated transcripts at the rDNA, Rio1 allows for rDNA condensation and segregation in late anaphase. These events finalize the genome transmission process. We identify Rio1 as an essential nucleolar housekeeper that integrates rDNA replication and segregation with ribosome biogenesis.

[Indexed for MEDLINE]

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