Related Experiment Video
Updated: Jun 28, 2025
11:04
A Cell Free Assay to Study Chromatin Decondensation at the End of Mitosis
Published on: December 19, 2015
10.3K
Entangling and disentangling mitotic chromosomes
1Genome Damage and Stability Centre, School of Life Sciences, Science Park Road, University of Sussex, Falmer, Brighton, East Sussex BN1 9RQ, UK.
Molecular Cell
|April 19, 2024
Summary
Cellular manipulation of long DNA fibers creates topological challenges. New research shows mitotic chromosomes are self-entangled, requiring topoisomerase II (TOP2) activity for disentanglement in late mitosis.
Area of Science:
- Molecular Biology
- Genetics
- Cell Biology
Background:
- DNA topology and its management are crucial for cellular processes.
- The challenges of managing extremely long DNA fibers within cells are not fully understood.
- Chromosome structure and organization during cell division present significant topological hurdles.
Purpose of the Study:
- To investigate the topological state of DNA within mitotic chromosomes.
- To identify the mechanisms responsible for resolving DNA entanglements during cell division.
- To elucidate the role of specific enzymes in managing DNA topology during mitosis.
Main Methods:
- Microscopy techniques to visualize chromosome structure.
- Biochemical assays to assess DNA topological states.
- Genetic manipulation to study the function of topoisomerase II (TOP2).
Main Results:
- Mitotic chromosomes exhibit self-entangled DNA structures.
- Topoisomerase II (TOP2) activity is essential for disentangling these structures.
- This disentanglement process is particularly active in late mitosis.
Conclusions:
- Mitotic chromosomes are inherently self-entangled.
- Topoisomerase II (TOP2) plays a critical role in resolving DNA topological challenges during cell division.
- Understanding these mechanisms is key to comprehending genome stability and accurate chromosome segregation.
Related Concept Videos
02:11Forces Acting on Chromosomes
3.3K
During mitosis, chromosome movements occur through the interplay of multiple piconewton level forces. In prometaphase, these forces help in chromosome assembly or congression at the equatorial plane, eventually leading to their alignment at the metaphase plate. The forces acting on the chromosomes are space and time-dependent; therefore, they vary with the position of the chromosomes as the cell progresses through mitosis.
Microtubules and motor proteins exert two types of forces on...
Microtubules and motor proteins exert two types of forces on...
3.3K
01:39Anaphase A and B
4.1K
Microtubules form through the end-to-end polymerization of tubulin heterodimers. Kinetochore microtubules originate from the spindle poles, and their plus-ends connect with the kinetochores on sister-chromatids. Ndc80 protein complexes, present on the kinetochore, form low-affinity links with the plus end of these kinetochore microtubules.
Plus-end depolymerization releases tubulin heterodimers from the terminal region of the microtubule. As tubulin subunits are lost, the Ndc80 complexes detach...
Plus-end depolymerization releases tubulin heterodimers from the terminal region of the microtubule. As tubulin subunits are lost, the Ndc80 complexes detach...
4.1K
02:27The Mitotic Spindle
6.6K
The mitotic spindle—or spindle apparatus—is a eukaryotic, cytoskeletal structure made up of long protein fibers called microtubules. Formed during cell division, the spindle separates sister chromatids and moves them to opposite ends of a parental cell, where the now individual chromosomes are distributed to two daughter cell nuclei.
The bipolar configuration of the mitotic spindle facilitates chromosomal segregation, preparing the cell for division. One mechanism that ensures...
The bipolar configuration of the mitotic spindle facilitates chromosomal segregation, preparing the cell for division. One mechanism that ensures...
6.6K
02:57Attachment of Sister Chromatids
3.3K
As cells progress into mitosis, the nuclear envelope breaks down, and the condensed chromosomes are exposed to the array of bipolar microtubules of the mitotic spindle. The kinetochore, a large, disc-shaped protein complex, is present at the centromere region of the sister chromatids and acts as a binding site for the microtubules. Usually, the plus-end of a single microtubule is embedded within the kinetochore. However, some kinetochores first establish lateral contact with the side-wall...
3.3K
02:17Separation of Sister Chromatids
3.6K
At the transition from prophase to metaphase, there is a reduction in cohesion along the chromosomal arms, resulting in the resolution of sister chromatids. However, residual cohesin connections remain to hold the sister chromatids together until the transition from metaphase to anaphase. The residual connection prevents any premature separation of sister chromatids, blocking the risks of aneuploidy within the daughter cells.
At the onset of anaphase, separase, a proteolytic enzyme, is...
At the onset of anaphase, separase, a proteolytic enzyme, is...
3.6K
02:20Cohesins
4.5K
Cohesin protein complexes are a molecular glue that holds two sister chromatids together. They play an important role both in mitosis and meiosis. In mitosis, all cohesin complexes present on the chromosomes are removed before the start of the anaphase stage.
Cohesin complexes in Meiotic Division
Meiosis involves two distinct rounds of chromosomal segregation and cell divisions— Meiosis I followed by Meiosis II – producing four daughter cells. Meiosis I includes the separation of...
Cohesin complexes in Meiotic Division
Meiosis involves two distinct rounds of chromosomal segregation and cell divisions— Meiosis I followed by Meiosis II – producing four daughter cells. Meiosis I includes the separation of...
4.5K