CLIP170-like tip1p spatially organizes microtubular dynamics in fission yeast

Rod-shaped fission yeast cells grow in a polarized manner, and unlike buddi ng yeast, the correct positioning of the growth sites at cell ends requires interphase microtubules. Here we describe a microtubule guidance mechanism that orients microtubules in the intracellular space along the long axis o f the cell, guiding them to their target region at the cell ends. This mech anism involves tip1p, a CLIP170-like protein that localizes to distal tips of cytoplasmic microtubules. In the absence of tip1p, microtubular catastro phe is no longer restricted to cell ends but occurs when microtubules reach any region of the cellular cortex. Thus, tip1p enables microtubules to dis criminate different cortical regions and regulates their dynamics according ly.