Tyr(less) kinase signaling during mitosis.

Tyrosine phosphorylation is rare, representing only about 0.5% of phosphorylations in the cell under basal conditions. While mitogenic tyrosine kinase signaling has been extensively explored, the role of phosphotyrosine signaling across the cell cycle and in particular during mitosis is poorly understood. Two recent, independent studies tackled this question from different angles to reveal exciting new insights into the role of this modification during cell division. Caron et al. 1 exploited mitotic phosphoproteomics data sets to determine the extent of mitotic tyrosine phosphorylation, and St-Denis et al. 2 identified protein tyrosine phosphatases from all subfamilies as regulators of mitotic progression or spindle formation. These studied collectively revealed that tyrosine phosphorylation may play a more prominent and active role in mitotic progression than previously appreciated.