The Role of Outer Kinetochore Proteins in Forming Load-Bearing Interactions with the Dynamic Microtubule Tip

Abstract

Mitosis, a biological process where newly duplicated DNA is condensed and segregated between a dividing cell, is an essential process for all eukaryotic systems. During mitosis, dynamic spindle microtubules, emanated from the spindle pole body, forms an interaction with the kinetochore. The kinetochore, a molecular machine composed of over 50 different proteins in budding yeast, is first assembled on a specific region on the chromosomes, known as the centromere, and connects with the spindle microtubule. The kinetochore plays many roles during chromosome segregation. 1) The kinetochore forms end-on attachments with the dynamic microtubule tip. 2). Once end-on attachments are made, the kinetochore ensures these interactions are load bearing. 3). Lastly, the kinetochore acts as a regulatory hub to ensure proper chromosome segregation. Here I investigate how the kinetochore forms load-bearing interactions with the dynamic microtubule tip. The two essential microtubule binding elements of the budding yeast kinetochore, Ndc80 and Dam1 complexes, interact with one another via three interaction regions. I found that two of these regions form load-bearing interactions between the Ndc80 and Dam1 complexes during microtubule assembling. These two regions are regulated by the Ipl1 kinase. All three interaction regions establish load-bearing interactions while on a disassembling microtubule tip.