Microtubule dynamics are regulated by plus-end tracking proteins (+TIPs), which localize to the plus-ends of microtubules (MTs). We previously showed that TACC1 and TACC3, members of the transforming acidic coiled-coil protein family, can act as +TIPs to regulate MT dynamics in Xenopus laevis Here, we characterize TACC2 as a +TIP that localizes to MT plus-ends, in front of EB1 and overlapping with TACC1 and TACC3, in multiple embryonic cell types. Moreover, we show that TACC2 can promote MT polymerization in mesenchymal cells but not in neuronal growth cones, thus displaying cell-type specificity. Structure-function analysis demonstrates that the C-terminal region of TACC2 is both necessary and sufficient to lo... More
Microtubule dynamics are regulated by plus-end tracking proteins (+TIPs), which localize to the plus-ends of microtubules (MTs). We previously showed that TACC1 and TACC3, members of the transforming acidic coiled-coil protein family, can act as +TIPs to regulate MT dynamics in Xenopus laevis Here, we characterize TACC2 as a +TIP that localizes to MT plus-ends, in front of EB1 and overlapping with TACC1 and TACC3, in multiple embryonic cell types. Moreover, we show that TACC2 can promote MT polymerization in mesenchymal cells but not in neuronal growth cones, thus displaying cell-type specificity. Structure-function analysis demonstrates that the C-terminal region of TACC2 is both necessary and sufficient to localize to MT plus-ends and promote increased rates of MT polymerization, while the N-terminal region cannot bind to MT plus-ends but can act in a dominant-negative capacity to reduce polymerization rates. Finally, we analyze mRNA expression patterns in Xenopus embryos for each TACC protein, and observe neural enrichment of TACC3 expression compared with TACC1 and TACC2, which are also expressed in mesodermal tissues including somites. Overall, these data provide a novel assessment of all three TACC proteins as a family of +TIPs by highlighting the unique attributes of each, as well as their collective characteristics.
