Research
?We study mitosis and a new link of mRNA translation to cell proliferation control
Activators of the ubiquitin ligase APC/C
Cyclin-dependent kinases (Cdks) are key regulators of the eukaryotic cell division cycle. Through phosphorylation a various target proteins, cyclinB-Cdk1 promotes early, but blocks late events of mitosis. Therefore, cyclinB proteolysis is important for the completion of nuclear and cell division. Building on work on the ubiquitin system (EMBO J 9:543-50; EMBO J 9:4535-41; TiBS 15:195-8; Nature 373:78-81), we identified a substrate recognition subunit (Hct1, a.k.a. Cdh1) of the anaphase-promoting complex (APC/C) as a regulator of cyclin B proteolysis in budding yeast (Cell 90:683-93; EMBO J 20: 5165-75). Phosphorylation by cyclin B-Cdk1 kinase was found to inhibit the APC/C-Cdh1 ubiquitination pathway (Science 282:1721-4). This antagonism is a fundamental aspect of eukaryotic cell cycle control. Recent work indicated that proteolysis by the APC/C-Cdh1 pathway is restricted to the cell nucleus in budding yeast (MBoC 26:843-58).?
Nuclear localization and APC/C binding of Cdh1 were found to be controlled through separate phosphorylation sites (MBoC 27:2198-212.
Yeast Cdh1 is activated in mitosis by Cdc14 phosphatase, a protein retained in the nucleolus for most of the cell cycle. Current efforts aim to better define the underlying mechanisms, among others by mapping domains of the Net1 nucleolar Cdc14 inhibitor and the related Tof2 protein (Curr Biol 18:1001-5).
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In another ongoing project we use confocal live cell imaging to study how proteins of the nucleolus are distributed during yeast mitosis. While the rDNA binding protein Fob1 segregated equally, RNA Pol I subunits and ribosome biogenesis factors predominated in the mother cell body, while other nucleolar proteins enriched in the daughter cell. We are various mutants affected in chromosome segregation or Pol I function to understand how this asymmetry in nucleolar protein segregation arises.
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Cdc123 required for translation initiation and cell cycle entry
The second research focus in the lab concerns Cdc123 and the question how this protein controls entry into the cell division cycle. Cdc123 is conserved among eukaryotes and indispensable for cell viability, but its mechanism of action has remained unknown. Through genetic and biochemical analysis, we found that Cdc123 serves an unanticipated, essential role in the onset of protein synthesis by assembling the translation factor eIF2 (JBC 288:21537-46). This GTP-dependent carrier of the initiator-tRNA is well known also for its regulatory role in the stress-induced reprogramming of gene expression. In a recent collaborative effort, the 3D-structure of Cdc123 was solved (Structure 23:1596-608). The work indicated that Cdc123 is an ATP-binding protein of the ATP-grasp enzyme family. Building on the structural information, we are developing various approaches to work out the molecular mechanism of eIF2 assembly by Cdc123 and the putative regulation of the process. This project is supported by the Deutsche Forschungsgemeinschaft through SFB960.
Methods
In our work we are using a range of methods including gene cloning and mutagenesis, PCR-mediated epitope tagging, fluorescence microscopy, flow cytometry, Y2H, Western and co-IP analysis, protein affinity purification, EMSA and ThermoFluor analysis.
Team
Team | ||
![]() | Prof. Dr. rer. nat.Wolfgang Seufert | |
![]() | Dr. rer. nat. Wolfgang Mages z.Zt. 100% Freistellung für T?tigkeit im Personalrat Geb?ude Westliche Naturwissenschaften D3_2.303 | |
![]() | Arlett Hirsch Geb?ude Westliche Naturwissenschaften D3_2.311 | |
wissenschaftliche Mitarbeiter | ||
![]() | Dr. rer. nat. Simone Fabian Postdoc Geb?ude Westliche Naturwissenschaften D3_2.317 Tel. 0941 943-3174 Labor-Durchwahl 3177 simone.fabian@ur.de | |
![]() | Dr. rer. nat. Philipp Girke | |
![]() | Dr. rer. nat. Lea Neumann-Arnold | |
![]() | Dr. rer. nat. Sophia Pinz | |
![]() | Julia Simmler | |
technische Mitarbeiter | ||
![]() | Andrea Brücher | |
![]() | Antje Machetanz-Morokane |