Cik1 and Vik1 accessory proteins confer distinct functions to the kinesin-14 Kar3.

The budding yeast Saccharomyces cerevisiae has a closed mitosis in which the mitotic spindle and the cytoplasmic microtubules (MTs), both of which generate forces to faithfully segregate chromosomes, remain separated by the nuclear envelope throughout the cell cycle. Kar3, the yeast kinesin-14, has distinct functions on MTs in each compartment. Here, we show that two proteins, Cik1 and Vik1, which form heterodimers with Kar3, regulate its localization and function within the cell, and along MTs in a cell cycle-dependent manner.

Microtubules are necessary for proper Reticulon localization during mitosis.

During mitosis, the structure of the Endoplasmic Reticulum (ER) displays a dramatic reorganization and remodeling, however, the mechanism driving these changes is poorly understood. Hairpin-containing ER transmembrane proteins that stabilize ER tubules have been identified as possible factors to promote these drastic changes in ER morphology. Recently, the Reticulon and REEP family of ER shaping proteins have been shown to heavily influence ER morphology by driving the formation of ER tubules, which are known for their close proximity with microtubules.

Microtubule dynamics regulation reconstituted in budding yeast lysates.

Microtubules (MTs) are important for cellular structure, transport of cargoes and segregation of chromosomes and organelles during mitosis. The stochastic growth and shrinkage of MTs, known as dynamic instability, is necessary for these functions. Previous studies to determine how individual MT-associated proteins (MAPs) affect MT dynamics have been performed either through studies, which provide limited opportunity for observation of individual MTs or manipulation of conditions, or studies, which focus either on purified proteins, and therefore lack cellular complexity, or on cell extracts made from genetically intractable organisms.

Proper symmetric and asymmetric endoplasmic reticulum partitioning requires astral microtubules.

Mechanisms that regulate partitioning of the endoplasmic reticulum (ER) during cell division are largely unknown. Previous studies have mostly addressed ER partitioning in cultured cells, which may not recapitulate physiological processes that are critical in developing, intact tissues. We have addressed this by analysing ER partitioning in asymmetrically dividing stem cells, in which precise segregation of cellular components is essential for proper development and tissue architecture.

Spatial reorganization of the endoplasmic reticulum during mitosis relies on mitotic kinase cyclin A in the early Drosophila embryo.

Mitotic cyclin-dependent kinase with their cyclin partners (cyclin:Cdks) are the master regulators of cell cycle progression responsible for regulating a host of activities during mitosis. Nuclear mitotic events, including chromosome condensation and segregation have been directly linked to Cdk activity. However, the regulation and timing of cytoplasmic mitotic events by cyclin:Cdks is poorly understood.

Altering membrane topology with Sar1 does not impair spindle assembly in Xenopus egg extracts.

Intracellular membrane networks including the endoplasmic reticulum (ER) and the Golgi apparatus experience dramatic reorganization upon entry into mitosis. However, the mechanisms driving these rearrangements and their importance for cell division are poorly understood. The GTPase Sar1 is a component of the secretory pathway and a key activator of anterograde transport of cargo from the ER to the Golgi.

Constitutive dynein activity in She1 mutants reveals differences in microtubule attachment at the yeast spindle pole body.

The organization of microtubules is determined in most cells by a microtubule-organizing center, which nucleates microtubule assembly and anchors their minus ends. In Saccharomyces cerevisiae cells lacking She1, cytoplasmic microtubules detach from the spindle pole body at high rates. Increased rates of detachment depend on dynein activity, supporting previous evidence that She1 inhibits dynein.

A quantitative, high-throughput reverse genetic screen reveals novel connections between Pre-mRNA splicing and 5' and 3' end transcript determinants.

Here we present the development and implementation of a genome-wide reverse genetic screen in the budding yeast, Saccharomyces cerevisiae, that couples high-throughput strain growth, robotic RNA isolation and cDNA synthesis, and quantitative PCR to allow for a robust determination of the level of nearly any cellular RNA in the background of ~5,500 different mutants. As an initial test of this approach, we sought to identify the full complement of factors that impact pre-mRNA splicing. Increasing lines of evidence suggest a relationship between pre-mRNA splicing and other cellular pathways including chromatin remodeling, transcription, and 3' end processing, yet in many cases the specific proteins responsible for functionally connecting these pathways remain unclear.