![]() ![]() We also find that prolonged metaphase stalling of cells leads to overloading of chromosomes with condensin, with abnormally high chromosome stiffness. Condensin depletion leads to a dramatic (~10 fold) reduction in chromosome elastic stiffness relative to the native, non-depleted case. We have combined micromanipulation of single human mitotic chromosomes, sub-nanonewton force measurement, siRNA interference of condensin subunit expression, and fluorescence microscopy, to analyze the role of condensin in large-scale chromosome organization. However, how condensins organize metaphase chromosomes is not understood. This process is thought to be largely controlled by the action of condensin SMC protein complexes on chromatin fibers. Where the second type of condensin, which is present in humans and other multicellular organisms, binds during cell division is another future line of enquiry.During cell division, chromosomes must be folded into their compact mitotic form to ensure their segregation. The OIST study concentrates on only one type of condensin. They further speculate that these eliminated macromolecules might be regenerated by the cellular machinery of the daughter cell when necessary.Īt this point, the relevant biochemical processes by which condensin works remain to be apprehended. The OIST researchers speculate that condensin is trimming the hedgerow of the genome during the replication and dividing phase. Norihiko Nakazawa, of OIST's G0 Cell Unit, the paper's first author. “While these macromolecules are important for the parent cell, they pose hindrances during cell division to segregating the copied chromosomes to daughter cells properly,” said Dr. Accommodating these extra structures into the daughter cell's nucleus might be what increases the overall cell size. Larger cells need more energy to survive and condensin could be crucial to maintaining appropriate DNA content and cell sizes across cellular generations.Įxtraneous structures like RNA and bound proteins are typically present along the length of chromosomes. ![]() DNA content in the mutant cells increased and some of the resulting cell sizes were larger. In this mutated strain, there were massive errors in disentangling the separately copied chromosomes from the original. The researchers also engineered a yeast strain where a mutant condensin was produced by the cell when it went into figurative labor. Hsp genes are a family of proteins produced by cells in stressful situations, ranging from high temperatures to ultraviolet light exposure to maintain genomic integrity. OIST researchers bumped up the heat from 20 degrees to 36 degrees centigrade over 9 minutes, and found that condensin accumulated around heat-shock protein (Hsp) genes after replication. Thus, condensin is crucial to passing on genes correctly.Ĭondensin also helps preserve the genome in challenging environments. In humans and all multicellular organisms, three different types of RNA producing enzymes control how genes are transcribed. Large amounts of condensin also accumulate at areas where RNA is created. In a lot of cancerous cells, the centromere has an unnatural shape, which could be caused by a malfunction in the relevant cell's scaffolding machinery. ![]() The OIST researchers found that the largest amount of condensin aggregates at the centromere, the central knot tying together the two replicated chromosomes. It also undergoes cell division by first creating copies of chromosomes like most human cells and has a very fast replication cycle, all of which facilitated the study. This type of yeast shares many important genes with us and also has one of the two known condensin complexes in humans. Researchers in OIST's G0 Cell Unit used fission yeast to find the binding sites of this particular protein complex along chromosomal DNA. The protein complex, called condensin, is one of many that become active when cells replicate. ![]()
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