XTACC3–?XMAP215 association reveals an asymmetric interaction promoting microtubule elongation
Gulnahar B. Mortuza, Tommaso Cavazza, Maria Flor Garcia-Mayoral, Dario Hermida, Isabel Peset, Juan G. Pedrero, Nekane Merino, Francisco J. Blanco, Jeppe Lyngsø, Marta Bruix,Jan Skov Pedersen, Isabelle Vernos & Guillermo Montoya
?chTOG is a conserved microtubule polymerase that catalyses the addition of tubulin dimers to promote microtubule growth. ?chTOG interacts with ?TACC3, a member of the transforming acidic coiled-coil (TACC) family. Here we analyse their association using the Xenopus homologues, ?XTACC3 (?TACC3) and ?XMAP215 (?chTOG), dissecting the mechanism by which their interaction promotes microtubule elongation during spindle assembly. Using SAXS, we show that the TACC domain (TD) is an elongated structure that mediates the interaction with the C terminus of ?XMAP215. Our data suggest that one TD and two ?XMAP215 molecules associate to form a four-helix coiled-coil complex. A hybrid methods approach was used to define the precise regions of the TACC heptad repeat and the ?XMAP215 C terminus required for assembly and functioning of the complex. We show that ?XTACC3 can induce the recruitment of larger amounts of ?XMAP215 by increasing its local concentration, thereby promoting efficient microtubule elongation during mitosis.
