Kinetochore - Kinetochore Function

Kinetochore Function

The number of MTs attached to one kinetochore is variable: in Saccharomyces cerevisiae only one MT binds each kinetochore, whereas in mammals there can be among 15-35 MTs bound to each kinetochore. However, not all the MTs in the spindle attach to one kinetochore. There are MTs that extend from one centrosome to the other (and they are responsible for spindle length) and some shorter ones are interdigitated between the long MTs. Professor B. Nicklas (Duke University), showed that, if one breaks down the MT-kinetochore attachment using a laser beam, chromatids can no longer move, leading to an abnormal chromosome distribution. These experiments also showed that kinetochores have polarity, and that kinetochore attachment to MTs emanating from one or the other centrosome will depend on its orientation. This specificity guarantees that only one chromatid will move to each spindle side, thus ensuring the correct distribution of the genetic material. Thus, one of the basic functions of the kinetochore is the MT attachment to the spindle, which is essential to correctly segregate sister chromatids. If anchoring is incorrect, errors may ensue, generating aneuploidy, with catastrophic consequences for the cell. To prevent this from happening, there are mechanisms of error detection and correction (as the spindle assembly checkpoint), whose components reside also on the kinetochores.The movement of one chromatid towards the centrosome is produced primarily by MT depolymerization in the binding site with the kinetochore. These movements require also force generation, involving molecular motors likewise located on the kinetochores.