β-tubulin carboxy-terminal tails exhibit isotype-specific effects on microtubule dynamics in human gene-edited cells

Microtubules are highly dynamic structures that play an integral role in fundamental cellular functions. Different α- and β-tubulin isotypes are thought to confer unique dynamic properties to microtubules. The tubulin isotypes have highly conserved structures, differing mainly in their C-terminal tail sequences. However, little is known about the importance of the C-terminal tail in regulating and co-ordinating microtubule dynamics. We developed syngeneic human cell models using gene-editing to precisely modify the β-tubulin C-terminal tail region while preserving the endogenous microtubule network. Fluorescent microscopy of live cells, coupled with advanced image analysis revealed that the β-tubulin C-terminal tails differentially co-ordinate the collective and individual dynamic behaviour of microtubules by affecting microtubule growth rates and explorative microtubule assembly in an isotype-specific manner. Furthermore, βI- and βIII-tubulin C-terminal tails differentially regulate the sensitivity of microtubules to tubulin-binding agents and the microtubule depolymerising protein MCAK. The sequence of the β-tubulin tail encodes regulatory information that instructs and co-ordinates microtubule dynamics, thereby fine-tuning microtubule dynamics to support cellular functions.