In a new study published online in the open access journal PLoS Biology, Philipp Niethammer, Eric Karsenti, and colleagues investigate the regulation of microtubule dynamics via application of their new method, called visual immunoprecipitation (VIP), which enables simultaneous visualization of multiple protein interactions in cell extracts.

When eukaryotic cells undergo cell division, a dramatic reorganization occurs during the transition from interphase to metaphase. The cell rounds up, chromosomes condense, the nuclear envelope breaks down, and microtubules (proteins that help maintain the cell's shape) become very short and dynamic before assembly of the mitotic spindle (the structure that pulls chromosomes apart). Although it is known that the CDK1 kinase induces this reorganization, the precise mechanisms that regulate such coordinated changes are not yet understood.

There are two known major regulators of microtubule dynamics: a stabilizer (XMAP215) and a destabilizer (XKCM1); a series of other molecules (EB1, APC, and CLIP 170) are also involved, although their roles in the global regulation of microtubule dynamic instability are not as clear. Using VIP, these researchers show that microtubules are stable during interphase because the destabilizer is inhibited by the other molecul es. During mitosis, however, the destabilizer is released, triggering the alteration of microtubule structure and dynamics. Thus, microtubule dynamics change in response to a dramatic switch in the interactions of a set of proteins.