The kinetochore proteins Pcs1 and Mde4 and heterochromatin are required to prevent merotelic orientation

Accurate chromosome segregation depends on the establishment of correct-amphitelic-kinetochore orientation. Merotelic kinetochore orientation is an error that occurs when a single kinetochore attaches to microtubules emanating from opposite spindle poles, a condition that hinders segregation of the kinetochore to a spindle pole in anaphase. To avoid chromosome missegregation resulting from merotelic kinetochore orientation, cells have developed mechanisms to prevent or correct merotelic attachment. A protein called Pcs1 has been implicated in preventing merotelic attachment in mitosis and meiosis II in the fission yeast S. pombe.