Dissection of fission yeast microtubule associating protein p93(Dis1): Regions implicated in regulated localization and microtubule interaction

Background: Fission yeast microtubule associating protein (MAP) p93(Dis1) functions for sister chromatid separation: dis1 mutants fail to separate chromosomes, while the spindle elongates but without cyclin destruction. p93(Dis1) microtubules in interphase cytoplasm, but shifts to the spindle pole body (SPB) and spindle microtubules upon the entry into mitosis. In this study, regions of p93(Dis1) were dissected to examine their role. Results: Nitrocellulose filter blotting shows that recombinant Dis1 binds to bovine brain microtubules in vitro. A basic central region rich in S, T and P is essential for this association. However, the whole p93(Dis1) with N- and C-termini containing a conserved repeat motif and heptad repeats, respectively, is necessary for normal microtubule association in vivo. The N-truncated region also binds to microtubules but only to the portions near the SPBs. Overproduction phenotypes indicate that p93(Dis1) greatly affects spindle formation and cell morphogenesis. The central region is essential but, by itself, not sufficient for generating such effects. Conclusions: We propose that p93(Dis1) consists of three regions which carry distinct properties for localization: the N-region for cell cycle dependent localization, the central region for direct microtubule association, and the C-region for SPB and nuclear localization. The essential role of p93(Dis1) is carried out in the C-region, while the N-region acts as a regulator.