Fig. 6. Identification and characterisation of Drosophila Tau as a candidate PAR-1 substrate. (A) Organisation of the tau locus, showing the intron/exon structure of tau (UTRs in white) and the location of the S10 gene and the EP element insertions within the first intron. The position of the deficiency uncovering tau, Df(3R)MR22(tau) is shown below. (B) Domain structure of human and Drosophila Tau, illustrating the percent identity (similarity) between the N-terminal projection domains and the MTBD repeats (in grey); an alignment of these repeats is shown below. The putative PAR-1 target serine within the KXGS motif is conserved in four of the five Drosophila repeats (arrowhead). (C) Western blot of 12-18 hour and tau mutant embryos probed with an antibody raised against the MT-binding domain of Drosophila Tau. (D) MT spin-down assay, revealing cosedimentation of Tau with Taxol-induced polymerised Tubulin in the pellet (P) fraction. In the absence of Taxol, both remain in the supernatant (S). (E) MT localisation of Tau:GFP in a living Drosophila ovary. (F) PAR-1 kinase assay with GFP:PAR-1 immunoprecipitated from ovarian extracts and MBP:Tau MTBD substrates, containing (KXGS) or lacking (KXGA) the four putative PAR-1 target sites. (G) Stage 10 egg chamber containing two large mutant clones for Df(3R)MR22(tau) stained for DaPKC (blue) and -tubulin (red). DaPKC and -tubulin localise normally in tau mutant clones.

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