Restoration of DNA structure shown to be prerequisite
Researchers at the University of Tokyo have discovered a long-overlooked process important for converting a long, string-like DNA molecule into a chromosome. This finding gives us a better understanding of the mechanism of how cells store safely genetic material, DNA.
DNA molecules are long, string-like polymers storing the genetic information of life and, in a cell, are tightly packed into structures called chromosomes. Formation of chromosomes in a dividing cell is required for faithful transmission of information in DNA to daughter cells. The condensin complex is known to play an essential role in assembling chromosomes, but it remains unknown how condensin is involved in folding of DNA molecules.
Researchers at the University of Tokyo, including Assistant Professor Takashi Sutani, Professor Katsuhiko Shirahige (Institute of Molecular and Cellular Biosciences) and Ph.D student Toyonori Sakata (Graduate School of Agricultural and Life Sciences), isolated from cells and analyzed DNA segments to which condensin binds, and revealed that condensin is associated with single-stranded DNA (ssDNA) which is produced by unwinding of the DNA double-helix.
By measuring the amount of ssDNA using an ssDNA binding protein, they found that ssDNA regions existed at expressed genes and were produced by gene expression (or transcription), and that ssDNA amount was further increased in condensin-deficient cells.
They also discovered that chromosome segregation defects in mutant cells that showed lowered levels of condensin function were largely rescued by transcription inhibition. They therefore concluded that ssDNA is produced by unwinding of double-stranded DNA during transcription, that ssDNA is detrimental to assembling chromosomes, and that condensin restores unwound ssDNA segments to double-stranded DNA.
“It was widely believed that unwound DNA segments return spontaneously to canonical double-helical DNA, but this study has revealed that restoration of double-stranded DNA is actively regulated and is important for cell survival. It has also demonstrated for the first time that the presence of ssDNA impedes chromosome organization, providing insight into the mechanism of chromosome formation,” says Assistant Professor Sutani.
This work was conducted in collaboration with the research group of Dr. Tatsuya Hirano (Chief Scientist at RIKEN Institute, Japan).
Condensin recognizes unwound DNA segments produced by gene expression and restores them to double-stranded DNA. This function proved to be a prerequisite for making chromosomes from DNA.
Takashi Sutani, Toyonori Sakata, Ryuichiro Nakato, Koji Masuda, Mai Ishibashi, Daisuke Yamashita, Yutaka Suzuki, Tatsuya Hirano, Masashige Bando & Katsuhiko Shirahige, "Condensin targets and reduces unwound DNA structure associated with transcription in mitotic chromosome condensation", Nature Communications Online Edition: 2015/7/23 (Japan time), doi: 10.1038/ncomms8815.
UTokyo Research article
Euan McKay | ResearchSea
Nanoparticle Exposure Can Awaken Dormant Viruses in the Lungs
16.01.2017 | Helmholtz Zentrum München - Deutsches Forschungszentrum für Gesundheit und Umwelt
Cholera bacteria infect more effectively with a simple twist of shape
13.01.2017 | Princeton University
Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.
While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...
Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales
Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...
Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.
As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...
At TU Wien, an alternative for resource intensive formwork for the construction of concrete domes was developed. It is now used in a test dome for the Austrian Federal Railways Infrastructure (ÖBB Infrastruktur).
Concrete shells are efficient structures, but not very resource efficient. The formwork for the construction of concrete domes alone requires a high amount of...
Many pathogens use certain sugar compounds from their host to help conceal themselves against the immune system. Scientists at the University of Bonn have now, in cooperation with researchers at the University of York in the United Kingdom, analyzed the dynamics of a bacterial molecule that is involved in this process. They demonstrate that the protein grabs onto the sugar molecule with a Pac Man-like chewing motion and holds it until it can be used. Their results could help design therapeutics that could make the protein poorer at grabbing and holding and hence compromise the pathogen in the host. The study has now been published in “Biophysical Journal”.
The cells of the mouth, nose and intestinal mucosa produce large quantities of a chemical called sialic acid. Many bacteria possess a special transport system...
10.01.2017 | Event News
09.01.2017 | Event News
05.01.2017 | Event News
17.01.2017 | Earth Sciences
17.01.2017 | Materials Sciences
17.01.2017 | Architecture and Construction