Mitotic control of condensin-mediated DNA loop extrusion

• Applicant: Professor Dr. Christian H. Häring
• Subject Area: Cell Biology ; Biochemistry
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 538955647

The mechanisms behind the formation of cylindrical mitotic chromosomes from a loose network of interphase chromatin fibers have puzzled biologists for more than a century. New research suggests that condensins - members of the structural maintenance of chromosomes (SMC) family of protein complexes - are DNA motors that achieve this task by harnessing the energy of ATP hydrolysis to extrude chromatin fibers into large arrays of loops. How their loop extrusion activity is tuned and, most importantly, restricted to the time of cell division has remained unknown. The work program outlined in this grant proposal aims to shed light into this fundamental question by investigating the control of the activities of the two human condensin complexes through phosphorylation by three major mitotic kinases. The study will be based on a defined experimental setup that uses condensin and kinase complexes purified to homogeneity in established enzymatic in vitro assays, including real-time imaging of DNA loop extrusion by single condensin complexes. This approach will allow the systematic dissection of the functional role of each kinase and their specific target sites in the near-mega-Dalton condensin complexes and, in combination with detailed structural information of the condensin reaction cycle, enable the formulation of a mechanistic model of condensin control. The implications of this model for condensin function in the formation and segregation of mitotic chromosomes will then be challenged in live human cultured cells.

• DFG Programme: Research Grants