Structural mechanisms of centromeric nucleation of the kinetochore complex

ongoing

Ensuring accurate segregation of the genetic material is an essential life process. In eukaryotes, such as humans and yeasts, regions of DNA known as centromeres nucleate the assembly of the megadalton kinetochore complex, which connects to and regulates spindle-microtubules that drive chromosome segregation. While significant progress has been made in the past decade in understanding the structural architecture of the inner kinetochore Ctf19 complex (CCAN in humans), a fundamental gap in knowledge remains concerning how the inner kinetochore is assembled upon native centromeric DNA. This gap is particularly important, as it addresses critical mechanistic steps involved in maintaining genome integrity across cell divisions, evolution, and disease. The budding yeast Saccharomyces cerevisiae is a fundamental model system for studying centromeres and kinetochores, as its kinetochores, the smallest known, represent the organizational module that, through repeated units, form larger kinetochores like those found in humans. In CENStruK, I will combine my background and expertise in yeast genetics and cell biology with the host lab’s expertise in mechanistic biochemistry, its large collection of proteins involved chromosome segregation, and its advanced electron microscopy facilities to fill this gap. CENStruK is divided into two complementary structural approaches. First, by harnessing required protein chaperones, I will reconstitute a key step in yeast’s inner kinetochore assembly that is required for recognition of its native centromere sequence. Second, I will deploy the ‘CentiCEN’ strain, which houses over 100 homogenized centromeres. This strain will be used in parallel for biophysical and structural studies of the endogenous CEN-kinetochore complex using cryo-EM and cryo-ET. My studies will not only shed light on a fundamental unknown in chromosome biology but will also inform future work in diverse eukaryotic species.