How do D-TACC and Msps/ch-TOG cooperate to stabilise centrosomal microtubules?
The distribution of MTs (red), DNA (blue) and either WT DTACC-GFP or DTACC-GFPS863L (in which the Aurora A phosphorylation site in D-TACC has been mutated to a leucine) (green). These GFP-fusions were expressed in a d-tacc mutant background, and so they are the only source of D-TACC. Note how both forms of D-TACC are concentrated at centrsosomes but the astral MTs are destabilised, while spindle MTs appear largely unperturbed, if D-TACC cannot be phosphorylated by Aurora A (see Barros et al., 2005).
We previously identified D-TACC as a novel centrosomal protein in Drosophila that interacts with MTs. We showed that TACC proteins are a conserved family of centrosomal proteins, and that D-TACC interacts with the MTs indirectly via the MT-interacting protein Msps (ch-TOG/XMAP215 in humans and frogs, respectively). In collaboration with the Hyman laboratory in Dresden, we have shown that TACC proteins are phosphorylated by Aurora A in both flies and frogs and that this phosphorylation occurs exclusively at centrosomes and is essential for the stabilisation of centrosomal MTs (Barros et al., 2005, Kinoshita et al., 2005). We suspect that the phosphorylation of D-TACC by Aurora A may allow the D-TACC/Msps complex to interact with, and stabilise, MT minus ends.