Biology subjects

Stumpff, J.

Publications and source records attributed to Stumpff, J..

3 recordsLinked to original sources

bioRxiv2018

The Human Kinesin Kif18A’s Neck Linker Permits Navigation of Microtubule Bound Obstacles within the Mitotic Spindle

Mitotic chromosome alignment is essential for the robust separation of genetic material into daughter cells. In mammalian cells, this process requires the function of Kif18A, a kinesin-8 motor protein. Kif18A confines chromosome movement to the mitotic spindle equator by accumulating at the plus-ends of kinetochore microtubule bundles (K-fibers), where it functions to suppress K-fiber dynamics. It is not understood how the motor accumulates at K-fiber plus-ends, a difficult feat requiring the motor to navigate protein dense microtubule tracks. Our data indicate that Kif18As relatively long (17 amino acid) neck linker is required for the motors accumulation at K-fiber plus-ends. Shorter neck linker (sNL) variants of Kif18A display a deficiency in K-fiber accumulation, especially on K-fibers near the center of the spindle. This pattern correlates with the more uniform concentration of the microtubule bundling protein HURP on central K-fibers compared to peripheral K-fibers. Depletion of HURP permits Kif18A sNL to accumulate on central K-fibers, while HURP overexpression reduces wild-type Kif18As ability to accumulate on this same K-fiber subset. Furthermore, single molecule assays indicate that Kif18A sNL motors are less proficient at navigating microtubules coated with the microtubule associated protein tau. Taken together, these results support a model in which Kif18As neck linker length permits efficient navigation of obstacles such as HURP to reach K-fiber ends during mitosis.\n\nSignficiance StatementKinesin motor proteins play key roles in controlling chromosome alignment and segregation during cell division. The kinesin Kif18A confines chromosomes to the middle of the spindle by accumulating at the ends of microtubules attached to chromosomes. We show here that Kif18As ability to accumulate at the end of these microtubules requires navigation of microtubule-associated protein obstacles, and that this activity is imparted by a relatively long neck linker region. These findings demonstrate a molecular mechanism for navigation of densely populated microtubules inside a cell.

cell biology↗

bioRxiv2018

Mitotic chromosome alignment is required for proper nuclear envelope reassembly

Chromosome alignment at the equator of the mitotic spindle is a highly conserved step during cell division, however, its importance to genomic stability and cellular fitness are not understood. Normal mammalian somatic cells lacking Kif18A function complete cell division without aligning chromosomes. These alignment-deficient cells display normal chromosome copy numbers in vitro and in vivo, suggesting that chromosome alignment is largely dispensable for maintenance of euploidy. However, we find that loss of chromosome alignment leads to interchromosomal compaction defects during anaphase, abnormal organization of chromosomes into a single nucleus at mitotic exit, and the formation of micronuclei in vitro and in vivo. These defects slow cell proliferation and reduce postnatal growth and survival with variable penetrance in mice. Our studies support a model in which the alignment of mitotic chromosomes promotes proper nuclear envelope reassembly and continued proliferation by ensuring that chromosomes segregate as a compact mass during anaphase.

cell biology↗

bioRxiv2018

Kinesin Binding Protein (KBP) buffers the activity of Kif18A and Kif15 in mitosis to ensure accurate chromosome segregation

Mitotic kinesins must be regulated to ensure a precise balance of spindle forces and accurate segregation of chromosomes into daughter cells. Here we demonstrate that Kinesin-Binding Protein (KBP) reduces the activity of KIF18A and KIF15 during metaphase. Overexpression of KBP disrupts the movement and alignment of mitotic chromosomes and decreases spindle length, a combination of phenotypes observed in cells deficient for KIF18A and KIF15, respectively. We show through gliding filament and microtubule co-pelleting assays that KBP directly inhibits KIF18A and KIF15 motor activity by preventing microtubule-binding. Consistent with these effects, the mitotic localizations of KIF18A and KIF15 are altered by overexpression of KBP. Cells depleted of KBP exhibit lagging chromosomes in anaphase, an effect that is recapitulated by KIF15 and KIF18A overexpression. Based on these data, we propose a model in which KBP acts as a protein buffer in mitosis, protecting cells from excessive KIF18A and KIF15 activity to promote accurate chromosome segregation.\n\nSUMMARYKinesin-Binding Protein (KBP) is identified as a regulator of the kinesins KIF18A and KIF15 during mitosis. KBP buffers the activity of these motors to control chromosome alignment and spindle integrity in metaphase and prevent lagging chromosomes in anaphase.

cell biology↗