TACC3 is a microtubule plus end-tracking protein that promotes axon elongation and also regulates microtubule plus end dynamics in multiple embryonic cell types.
Bottom Line: Using high-resolution live-imaging data on tagged +TIPs, we show that TACC3 localizes to the extreme microtubule plus end, where it lies distal to the microtubule polymerization marker EB1 and directly overlaps with the microtubule polymerase XMAP215.TACC3 also plays a role in regulating XMAP215 stability and localizing XMAP215 to microtubule plus ends.Taken together, our results implicate TACC3 as a +TIP that functions with XMAP215 to regulate microtubule plus end dynamics.
Affiliation: Department of Biology, Boston College, Chestnut Hill, MA 02467.Show MeSH
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Mentions: It is well established that the growing end of a MT is home to many different +TIPs, including EB1, CLASP, and XMAP215 (Akhmanova and Steinmetz, 2008). Different +TIPs have overlapping yet unique localizations on the ends of the MTs, depending on their particular binding affinities. XMAP215 is known as the distalmost +TIP, and EB1 is located directly behind it on MTs (Nakamura et al., 2012; Maurer et al., 2014). Most other +TIPs, including CLASP, partially overlap with EB1 and trail further behind it (Hur et al., 2011). Because the fly orthologue of TACC3 genetically interacts with CLASP (Long et al., 2013), yet TACC3 biochemically interacts with XMAP215 (Kinoshita et al., 2005; O'Brien et al., 2005; Peset et al., 2005), we examined where TACC3 specifically localized on the MT plus end. We performed sequential imaging of red and green channels in both time orders to compare colocalizations between the two proteins. Although this type of dual-image-comparison analysis allowed for the analysis of colocalization dynamics, we also calculated the frame-to-frame velocity of the growing MT plus end in order to account for the 1-s time delay between channels for each examined MT and used these measurements to translate one channel in the x-axis to obtain the final images in Figure 6. We also used these time-corrected images for measuring approximate distances between peak intensity values.
Affiliation: Department of Biology, Boston College, Chestnut Hill, MA 02467.