June 2016 | Volume 213, No. 6
People & Ideas
- A Rab3a-dependent complex essential for lysosome positioning and plasma membrane repair
Encarnação et al. show that Rab3a, together with its newly identified effector NMHC IIA, mediates the positioning of peripheral lysosomes in nonsecretory cells, thereby promoting lysosome exocytosis and plasma membrane repair.
- Local RhoA activation induces cytokinetic furrows independent of spindle position and cell cycle stage
Using optogenetics to obtain spatiotemporal control of RhoA activation, Wagner and Glotzer show that local RhoA activation is sufficient to induce cytokinetic furrowing. Furrows can be induced at both the cell equator and cell poles during various stages of mitosis, and cell rounding allows active RhoA to induce furrows in interphase.
- A noncatalytic function of the topoisomerase II CTD in Aurora B recruitment to inner centromeres during mitosis
The C-terminal domain (CTD) of Topo II is dispensable for its catalytic activity yet essential for Topo II function in chromosome segregation during mitosis. Here, Edgerton et al. resolve the role of the Topo II CTD during mitosis in yeast, showing that it functions noncatalytically via the Haspin-H3 T3-Phos pathway to recruit Ipl1/Aurora B to mitotic inner centromeres.
- SUMOylation of DNA topoisomerase IIα regulates histone H3 kinase Haspin and H3 phosphorylation in mitosis
Yoshida et al. show that mitotic SUMOylation of TOP2A C-terminal domain promotes its association with phosphorylated Haspin kinase through Haspin’s SUMO-interacting motifs to regulate recruitment of Aurora B kinase at mitotic centromeres.
- Divergent regulation of functionally distinct γ-tubulin complexes during differentiation
Differentiation induces loss of centrosomal microtubule organizing activity in many cell types, though the underlying mechanisms are poorly understood. Using the epidermis, Muroyama et al. show that cell cycle exit causes loss of a Nedd1–γ-tubulin complex, which is required for anchoring microtubules at the centrosome. This defines a novel function for γ-tubulin complexes in microtubule anchoring at the centrosome.
- Limited ER quality control for GPI-anchored proteins
Sikorska et al. find that remodeling of a GPI anchor after its attachment to proteins inside the ER strongly promotes ER export but occurs independently of protein folding, thereby effectively limiting ER quality control, potentially including ER-associated degradation of all GPI-anchored proteins.
- An actin-dependent annexin complex mediates plasma membrane repair in muscle
Demonbreun et al. visualized muscle membrane repair in real time after laser-induced microdamage. Annexin proteins were observed to form a repair cap at the site of injury, supporting a shoulder-like structure containing EHD1, EHD2, dysferlin, and MG53.