Spindles get the Ran around

Despite its fundamental role in cell division, the mitotic spindle remains an enigmatic figure in cell biology. This is due to the complex dynamic beh aviour of microtubules, which form the spindle fibres responsible for segre gating chromosomes to opposite ends of the cell during mitosis. Recent repo rts indicate that the small GTPase Ran, which plays a key role in nuclear t ransport, also has a role in mitosis by regulating microtubule nucleation a nd/or growth. The race is now on to determine how Ran exerts ifs effects on spindle assembly.