Centromeres: getting a grip of chromosomes

On monocentric chromosomes the centromere is the chromosomal site at which the kinetochore complex is assembled. This complex mediates the attachment and movement of chromosomes along spindle microtubules. The centromere is u sually the last site to retain cohesion between sister centromeres. The loc ation of the main sensor for defective spindle assembly at the kinetochore allows the release of this cohesion, and thus progression through mitosis, to be held in check until key events have been completed. The intricate nat ure of the centromere-kinetochore complexes and the events they co-ordinate and react to is presently being dissected by studies in several organisms. In particular, several new kinetochore proteins have been identified in ma ny organisms over the last year.