Stabilising and destabilising kinesin complexes queue at plus tips to ensure microtubule catastrophe at cell ends

In fission yeast, the length of interphase microtubule (iMT) arrays are adapted to cell length so as to maintain cell polarity and to help centre the nucleus and cell division ring. Here we show that length regulation of iMTs is dictated by spatially-regulated competition between MT-stabilising Tea2/Tip1/Mal3 (Kinesin-7) and MT-destabilising Klp5/Klp6/Mcp1 (Kinesin-8) complexes at iMT plus tips. During MT growth, the Tea2/Tip1/Mal3 complex remains bound to the plus tips of iMT bundles and restricts access to the plus tips by Klp5/Klp6/Mcp1, which accumulates behind it. At cell ends, Klp5/Klp6/Mcp1 invades the space occupied by the Tea2/Tip1/Tea1 kinesin complex triggering its displacement from iMT plus tips and MT catastrophe. These data show that in vivo, whilst the \"antenna model\" for iMT length- and age-dependent catastrophase accumulation has validity, length control is an emergent property reflecting spatially-regulated competition between multiple complexes at the MT plus tip.