Anaphase B: Long-standing models meet new concepts.

Mitotic cell divisions ensure stable transmission of genetic information from a mother to daughter cells in a series of generations. To ensure this crucial task is accomplished, the cell forms a bipolar structure called the mitotic spindle that divides sister chromatids to the opposite sides of the dividing mother cell. After successful establishment of stable attachments of microtubules to chromosomes and inspection of connections between them, at the heart of mitosis, the cell starts the process of segregation. This spectacular moment in the life of a cell is termed anaphase, and it involves two distinct processes: depolymerization of microtubules bound to chromosomes, which is also known as anaphase A, and elongation of the spindle or anaphase B. Both processes ensure physical separation of disjointed sister chromatids. In this chapter, we review the mechanisms of anaphase B spindle elongation primarily in mammalian systems, combining different pioneering ideas and concepts with more recent findings that shed new light on the force generation and regulation of biochemical modules operating during spindle elongation. Finally, we present a comprehensive model of spindle elongation that includes structural, biophysical, and molecular aspects of anaphase B. • Overview of spindle elongation dynamics in the context of different mitotic phases. • Synopsis of pioneering ideas and recent structural literature on metaphase and anaphase spindles in human cells. • Dissection of force-generation mechanisms during anaphase B and experimental support for their existence in mammals. • Description of changes in protein localization after metaphase-to-anaphase transition for a large set of spindle proteins. • Detailed molecular models of key aspects of anaphase B and their temporal regulation. [ABSTRACT FROM AUTHOR]