Living cells depend absolutely on tubulin, a protein that forms hollow tube-like polymers, called microtubules, that form scaffolding for moving materials inside the cell. Tubulin-based microtubule scaffolding allows cells to move, keeps things in place or moves them around. When cells divide, microtubule fibers pull the chromosomes apart into new cells. Cells with defects in tubulin polymerization die.
Microtubule fibers are hollow rods made of much smaller tubulin subunits that spontaneously assemble at one end of the rod, but exactly how they do this inside the crowded environment of living cells has been a mystery. Now researchers at UC Davis have uncovered the mechanism that puts these blocks in place, illustrated in a new animation.
By Greg Watry
Within every cell is a transportation system that rivals our most complex roadways and interchanges. Known collectively as the cytoskeleton, this system is used by molecular machines called motor proteins to transport cargo throughout the cell. It’s also essential to the vital process of cell division.
Image of the mitotic spindle in a human cell showing microtubules in green, chromosomes (DNA) in blue, and kinetochores in red. (Wikimedia Commons)
Where would we be without meiosis and recombination? For a start, none of us sexually reproducing organisms would be here, because that’s how sperm and eggs are made. And when meiosis doesn’t work properly, it can lead to infertility, miscarriage, birth defects and developmental disorders.
Neil Hunter’s laboratory at the UC Davis College of Biological Sciences is teasing out the complex details of how meiosis works. In a new paper published online Jan. 6 in the journal Science, Hunter’s group describes new key players in meiosis, proteins called SUMO and ubiquitin and molecular machines called proteasomes. Ubiquitin is already well-known as a small protein that “tags” other proteins to be destroyed by proteasomes (wood chippers for proteins). SUMO is a close relative of ubiquitin.
Full post: New Steps in the Meiosis Chromosome Dance
(809 words, 2 images, estimated 3:14 mins reading time)
“Gnothi seauton” or “Know thyself,” said the Ancient Greeks; but they might have also said, “eat yourself.” For biologists, autophagy or “self-eating” is the process that cells use to recycle material inside the cell. It breaks down defective proteins and molecules, disposes of invading viruses and bacteria, provides an energy source when food is lacking and generally keeps cells fit and healthy. Problems in autophagy are implicated in cancer, aging, infectious disease and degenerative disorders.
Yoshinori Ohsumi after hearing he had been awarded the 2016 Nobel Prize in Physiology or Medicine.
Photo: Mari Honda
Full post: Nobel Medicine Prize for “self-eating”
(307 words, 1 image, estimated 1:14 mins reading time)