Abstract

Recently, the EB1 and XMAP215/TOG families of microtubule binding proteins have been demonstrated to bind autonomously to the growing plus ends of microtubules and regulate their behaviour in in vitro systems. However, their functional redundancy or difference in cells remains obscure. Here, we compared the nanoscale distributions of EB1 and ch-TOG along microtubules using high-resolution microscopy techniques, and also their roles in microtubule organisation in interphase HeLa cells. The ch-TOG accumulation sites protruded ∼100 nm from the EB1 comets. Overexpression experiments showed that ch-TOG and EB1 did not interfere with each other’s localisation, confirming that they recognise distinct regions at the ends of microtubules. While both EB1 and ch-TOG showed similar effects on microtubule plus end dynamics and additively increased microtubule dynamicity, only EB1 exhibited microtubule-cell cortex attachment activity. These observations indicate that EB1 and ch-TOG regulate microtubule organisation differently via distinct regions in the plus ends of microtubules.

Highlights

  • In cells, microtubule dynamics and organisation are controlled by a variety of microtubule regulators

  • We showed that end-binding 1 (EB1) and ch-TOG have similar effects on overall microtubule dynamicity, while EB1 as well as EB3, but not ch-TOG, exhibited microtubule-cell cortex attachment activity

  • We used the high-resolution structured illumination microscopy (SIM) imaging technique to carefully compare the distributions of endogenous EB1 and chTOG at microtubule ends in HeLa cells cultured on collagencoated cover glasses (Figure S1 and Text S1)

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Summary

Introduction

Microtubule dynamics and organisation are controlled by a variety of microtubule regulators. The lengths and positions of microtubules in cells are appropriately controlled by microtubule plus-end-binding proteins that target the microtubule plus ends [1,2]. Among these molecules, end-binding 1 (EB1) family proteins and XMAP215/TOG family proteins have been demonstrated to autonomously bind to growing microtubule ends and regulate microtubule dynamics in in vitro reconstituted systems [3,4,5]. The mammalian homologue of XMAP215, hepatic tumour overexpressed gene (chTOG) [9], promotes microtubule assembly in vitro [10]

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