Comparative Analysis of Cohesin, Shugoshin and APC/C in Mitosis versus Meiosis

• Applicant: Professor Dr. Olaf Stemmann
• Subject Area: Cell Biology
• Term: from 2009 to 2016
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 116471507

Erroneous distribution of homologous chromosomes during female meiosis I is the major genetic cause of miscarriage and mental retardation in humans. Yet, the molecular mechanisms of genome haploidization remain poorly understood. We propose to study novel functions and regulations of three key players of the chromosome cycle: Cohesin, a ring-shaped protein complex that keeps sister chromatids paired, shugoshin, a protector of cohesion, and the APC/C (anaphase-promoting complex or cyclosome), a multi-subunit ubiquitin ligase and antagonist of cohesion which triggers chromosome segregation. We have previously shown that cohesin and shugoshin function also at centrosomes, which might explain why the centrosome cycle is usually coordinated with the chromosome cycle. Now, we will fine-map cohesin's centrosomal localization by electron microscopy, try to identify its substrate and investigate how centriole duplication is uncoupled from DNA replication in spermatocytes. Furthermore, we will identify determinants of the mutual exclusive function of shugoshin variants at chromosomes or centrosomes and investigate how shugoshin is inactivated after meiosis I to allow for the separation of dyads in meiosis II. Extending recent work, we will uncover the molecular mechanism of how the essential peptidyl-prolyl cis-trans isomerase Pin1 contributes to the spindle assembly checkpoint to restrict APC/C activity. Finally, we will isolate APC/C from different phases of meiosis, compare subunit compositions and substrate specificities and thereby gain new insight into the timing of meiosis by regulated activity of this crucial E3 ligase.

• DFG Programme: Priority Programmes
• Subproject of: SPP 1384: Mechanisms of Genome Haploidisation