Identification of novel factors that organize mitotic and meiotic chromosomes

• Applicant: Professor Dr. Christian H. Häring
• Subject Area: Cell Biology
• Term: from 2009 to 2015
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 116325492

• Final Report Year: 2015

Final Report Abstract

The formation of structured rod-shaped chromosomes is a key prerequisite for their proper segregation during mitotic and meiotic cell divisions. Despite considerable efforts over a period of several decades, the knowledge about the molecular machinery underlying this chromosome condensation process has remained largely incomplete. In order to reveal yet undiscovered factors involved in chromosome condensation, we developed an imaging-based assay system to measure condensation dynamics in live fission yeast cells. We demonstrated that our new assay is capable of providing a quantitative and time-resolved read-out for the changes in longitudinal chromosome compaction during mitosis and meiosis by tracking, with high spatial and temporal resolution, the distances between two fluorescent markers located on the same chromosome. By imaging a large number of cells in parallel and automation of imaging and analysis pipelines, we were able to screen a newly generated collection of conditional fission yeast mutants for defects in condensation. This screen identified, in addition to proteins with already known functions in chromosome condensation, including all five subunits of the condensin complex and topoisomerase II, several novel candidates as chromosome condensation factors. Notably, we identified three independent candidates with mutations in zas1, a gene with previously unknown function. Consistent with a role in the formation of mitotic chromosomes, inactivation of zas1 significantly altered the dynamics of condensation and resulted in chromosome segregation defects. Studies to reveal the detailed molecular mechanisms of Zas1 activity during chromosome condensation are ongoing. Further studies using our condensation assay supported the involvement of posttranslational chromatin modifications, including histone acetylation and deacetylation, in the formation of mitotic chromosomes. We are currently following up on our discoveries to understand the mechanistic basis of mitotic and meiotic chromosome condensation.

Publications

• Condensin structures chromosomal DNA through topological links. Nature Structural and Molecular Biology 18 (2011), 894-901
  S Cuylen, J Metz, and CH Haering
  
• Deciphering condensin’s actions during chromosome segregation. Trends in Cell Biology 21 (2011), 552-559
  S Cuylen and CH Haering
  
• Cohesin in determining chromosome architecture. Experimental Cell Research 318 (2012), 1386-1393
  CH Haering and R Jessberger
  
• Entrapment of chromosomes by condensin rings prevents their breakage during cytokinesis. Developmental Cell 27 (2013), 469­478
  S Cuylen, J Metz, A Hruby, and CH Haering
  
• Quantitative analysis of chromosome condensation in fission yeast. Molecular and Cellular Biology 33 (2013), 984-998
  B Petrova, S Dehler, T Kruitwagen, J-K Heriche, K Miura, and CH Haering
  
• Integration of biological data by kernels on graph nodes allows prediction of new genes involved in mitotic chromosome condensation. Molecular Biology of the Cell 25 (2014), 2522-2536
  JK Heriche, JG Lees, I Morilla, T Walter, B Petrova, M Julia Roberti, MJ Hossain, P Adler, JM Fernandez, M Krallinger, CH Haering, J Vilo, A Valencia, JA Ranea, C Orengo, J Ellenberg
  
• Control of chromosome interactions by condensin complexes. Current Opinion in Cell Biology 34 (2015), 94-100
  Y Frosi and CH Haering
  
• Shaping mitotic chromosomes: From classical concepts to molecular mechanisms. BioEssays 37 (2015), 755-766
  M Kschonsak and CH Haering