The faithful segregation of DNA during mitosis is critical to the life of a cell. A complex molecular machine called the mitotic spindle mediates this task. The spindle is made up of microtubule-binding proteins and microtubules on which the chromosomes are segregated. A complete understanding of the formation of the bipolar spindle and the mechanism of chromosome movement on the spindle remains elusive. Many key players in this process have been identified, and we are beginning to understand the various classes of proteins and their functions. However, not surprisingly, new players with potentially novel modes of action continue to be discovered. In this issue, Inoue and colleagues describe a novel microtubule-associated protein encoded by the Drosophila gene orbit that influences the structure of the spindle and binds microtubules in a GTP-dependent manner (Inoue et al. 2000).
Microtubules...
