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
Water forms 'spine of hydration' around DNA, group finds
26.05.2017 | Cornell University
How herpesviruses win the footrace against the immune system
26.05.2017 | Helmholtz-Zentrum für Infektionsforschung
Staphylococcus aureus is a feared pathogen (MRSA, multi-resistant S. aureus) due to frequent resistances against many antibiotics, especially in hospital infections. Researchers at the Paul-Ehrlich-Institut have identified immunological processes that prevent a successful immune response directed against the pathogenic agent. The delivery of bacterial proteins with RNA adjuvant or messenger RNA (mRNA) into immune cells allows the re-direction of the immune response towards an active defense against S. aureus. This could be of significant importance for the development of an effective vaccine. PLOS Pathogens has published these research results online on 25 May 2017.
Staphylococcus aureus (S. aureus) is a bacterium that colonizes by far more than half of the skin and the mucosa of adults, usually without causing infections....
Physicists from the University of Würzburg are capable of generating identical looking single light particles at the push of a button. Two new studies now demonstrate the potential this method holds.
The quantum computer has fuelled the imagination of scientists for decades: It is based on fundamentally different phenomena than a conventional computer....
An international team of physicists has monitored the scattering behaviour of electrons in a non-conducting material in real-time. Their insights could be beneficial for radiotherapy.
We can refer to electrons in non-conducting materials as ‘sluggish’. Typically, they remain fixed in a location, deep inside an atomic composite. It is hence...
Two-dimensional magnetic structures are regarded as a promising material for new types of data storage, since the magnetic properties of individual molecular building blocks can be investigated and modified. For the first time, researchers have now produced a wafer-thin ferrimagnet, in which molecules with different magnetic centers arrange themselves on a gold surface to form a checkerboard pattern. Scientists at the Swiss Nanoscience Institute at the University of Basel and the Paul Scherrer Institute published their findings in the journal Nature Communications.
Ferrimagnets are composed of two centers which are magnetized at different strengths and point in opposing directions. Two-dimensional, quasi-flat ferrimagnets...
An Australian-Chinese research team has created the world's thinnest hologram, paving the way towards the integration of 3D holography into everyday...
24.05.2017 | Event News
23.05.2017 | Event News
22.05.2017 | Event News
26.05.2017 | Life Sciences
26.05.2017 | Life Sciences
26.05.2017 | Physics and Astronomy