Haspin: a mitotic histone kinase required for metaphase chromosome alignment

The fidelity of chromosome segregation during cell division is critical to maintain genomic stability and to prevent cancer and birth defects. A key set of kinases that regulates this process has been identified and characterized over the last few years, including the Aurora, Polo and Nek families. Recently we proposed that a little-studied kinase known as haspin is a new member of this important group. During mitosis haspin is phosphorylated, associates with the chromosomes, centrosomes and spindle, and is responsible for phosphorylation of histone H3 at threonine-3. Depletion of haspin using RNA interference prevents normal alignment of chromosomes at metaphase, suggesting that haspin plays a crucial role in chromosome segregation. Here we discuss possible mechanisms of haspin action and the function of histone phosphorylation in mitosis. We also outline some of the questions raised by these new findings and consider what role haspin might play in cancer.