In the latest issue of JCB, two papers reveal that the enzyme Sac2 is a phosphoinositide 4-phosphatase that localizes to early endosomes and hydrolyzes PI(4)P. As explained in this week’s In Focus, Nakatsu et al. reveal that Sac2 teams up with the 5 phosphatase OCRL to remove endosomal PI(4,5)P2, while Hsu et al. show that, in the absence of Sac2, PI(4)P accumulates on early endosomes and inhibits endocytic recycling and slows cell migration.
Tsaalbi-Shtylik et al. describe how DNA mismatch repair proteins suppress UV-induced mutagenesis. As summarized here, the mismatch repair proteins Msh2 and Msh6 recognize nucleotides incorrectly incorporated opposite UV-damaged bases by the error-prone process of translesion synthesis, triggering their removal and the activation of DNA damage-signaling and cell cycle arrest.
Roberson et al. demonstrate that the transmembrane protein Tmem231, whose gene is mutated in both Meckel syndrome and orofaciodigital syndrome type 3, regulates ciliary membrane composition by organizing the organelle’s transition zone. More here.
Scheffler et al. reveal how two minus end-directed microtubule motors work in parallel to bring haploid nuclei together during fission yeast mating. As explained here, the kinesin motor Klp2 localizes to microtubules emanating from the spindle pole bodies associated with each haploid nucleus, and could potentially bring the nuclei together by sliding antiparallel microtubules past each other. Dynein, in contrast, localizes to the spindle pole bodies themselves, where it might pull on microtubules emanating from the other nucleus once Klp2 has brought them into close proximity.
And Juanes-Garcia et al. describe how a short, serine-rich motif in the non-helical tail domain of myosin II-B enables this motor protein to form stable actomyosin bundles that define the rear of migrating mesenchymal cells. Fenix and Burnette provide a commentary on the finding’s significance here, and senior author Miguel Vicente-Manzanares discusses his lab’s work in this month’s biosights video podcast. You can watch below or subscribe in iTunes.
That’s all for today, but you can find lot’s of other interesting papers to read on our table of contents here.
Cover image showing Tmem231 (green) at the ciliary transition zone between the basal body (red) and axoneme (blue) © 2015 Roberson et al.