The role of ChlR1 in DNA replication, DNA damage repair and cohesion establishment

Abstract

Sister chromatid cohesion is essential for the equal distribution of genetic material in mitosis. The cohesin complex plays a central role in the establishment of sister chromatid cohesion. The cohesin complex is a ring shaped structure that encircles sister chromatids prior to the onset of anaphase ensuring equal distribution of genetic material. The DEAD/H DNA helicase ChlR1 is important in the establishment of sister chromatid cohesion. ChlR1 interacts with the cohesin complex and is required for the loading of cohesin onto DNA. Cohesin is loaded onto the DNA during DNA replication. Here I identified a novel interacting partner of ChlR1. The multifunctional DNA binding protein FHL2 was shown to interact with ChlR1, and FHL2 was shown to have a role in sister chromatid cohesion since depletion of FHL2 resulted in abnormal metaphase spreads and reduced centromeric cohesion. These sister chromatid cohesion defects also result in a G₂/M delay. Here I show an additional function of ChlR1 in the repair of DNA damage. ChlR1 was required for the repair of DNA double strand breaks and ChlR1 was recruited to DNA double strand breaks. Furthermore the function of ChlR1 in DNA double strand break repair is S phase specific. This suggests that ChlR1 is important in the homology recombination repair pathway. I also show that ChlR1 is important in DNA replication. Depletion of ChlR1 results in inefficient DNA replication. In addition depletion of ChlR1 results in defects in DNA replication after hydroxyurea treatment. The results in this thesis shed light on novel functions of the DNA helicase ChlR1 in DNA replication and DNA damage repair and the multifunctional DNA binding protein FHL2 in cohesion establishment.