Most genetic information is directly encoded by the sequence of nucleotides in a chain of DNA, but further instructions may also be provided by adding chemical modifications to those nucleotides, just like inserting footnotes can alter the meaning of a text. One important modification is DNA methylation, which generally has the effect of ‘silencing’ transcriptional activity of marked genes—a secondary but essential level of regulation.
DNA methylation patterns can be transmitted from parent to child, an important process known as genomic ‘imprinting.’ Maintaining these patterns is an active process, as each cycle of DNA replication results in the production of chains that are only hemimethylated, and full methylation is subsequently restored by the enzyme DNA methyltransferase 1 (Dnmt1).
Other proteins are known to assist this process. Recent work from a group led by Haruhiko Koseki of the RIKEN Research Center for Allergy and Immunology in Yokohama, and Masaki Okano of the RIKEN Center for Developmental Biology in Kobe, has highlighted the important role of one particular protein, Np95, in directing Dnmt1 to hemimethylated DNA targets (1).
Koseki’s group initially found that Np95 associates with imprinting-related proteins, and subsequent experiments in mouse embryonic stem cells (ESCs) extended these findings, demonstrating that Np95 co-localizes with Dnmt1 and other associated proteins at hemimethylated chromosomal regions after DNA replication (Fig. 1). Eliminating the expression of Np95 altogether resulted in a marked reduction of DNA methylation in cultured ESCs, and led to full developmental arrest in mouse embryos.
Methylation does more than silence genes; it also helps stabilize DNA elements known as retrotransposons, which are otherwise capable of physically ‘jumping’ into other chromosomal regions—and potentially disrupting other genes. Koseki’s group found that Np95 helps to lock down these retrotransposons. “At the least, Np95 is essential to maintain genomic imprinting, which in turn permits normal development of embryonic and extraembryonic tissues,” he says. “But it could be possible that this process may also be important to ensure genomic stability.”
Intriguingly, Koseki’s and his colleagues also found evidence suggesting that Np95’s function may not be limited to restoring DNA methylation, but could encompass other chromosomal maintenance tasks as well—a possibility he is keen to investigate further. “Hemimethylated DNA is not simply a transient status that appears after DNA replication … it may potentially form a specific signal that could be sensed by Np95,” he says. “We presume that Np95 may form a platform that helps to organize not only DNA methylation but also other types of modifications.”
1. Sharif, J., Muto, M., Takebayashi, S., Suetake, I., Iwamatsu, A., Endo, T.A., Shinga, J., Mizutani-Koseki, Y., Toyoda, T., Okamura, K. et al. The SRA protein Np95 mediates epigenetic inheritance by recruiting Dnmt1 to methylated DNA. Nature 450, 908–912 (2007).
Saeko Okada | ResearchSEA
Study shines light on brain cells that coordinate movement
26.06.2017 | University of Washington Health Sciences/UW Medicine
New insight into a central biological dogma on ion transport
26.06.2017 | Aarhus University
An international team of scientists has proposed a new multi-disciplinary approach in which an array of new technologies will allow us to map biodiversity and the risks that wildlife is facing at the scale of whole landscapes. The findings are published in Nature Ecology and Evolution. This international research is led by the Kunming Institute of Zoology from China, University of East Anglia, University of Leicester and the Leibniz Institute for Zoo and Wildlife Research.
Using a combination of satellite and ground data, the team proposes that it is now possible to map biodiversity with an accuracy that has not been previously...
Heatwaves in the Arctic, longer periods of vegetation in Europe, severe floods in West Africa – starting in 2021, scientists want to explore the emissions of the greenhouse gas methane with the German-French satellite MERLIN. This is made possible by a new robust laser system of the Fraunhofer Institute for Laser Technology ILT in Aachen, which achieves unprecedented measurement accuracy.
Methane is primarily the result of the decomposition of organic matter. The gas has a 25 times greater warming potential than carbon dioxide, but is not as...
Hydrogen is regarded as the energy source of the future: It is produced with solar power and can be used to generate heat and electricity in fuel cells. Empa researchers have now succeeded in decoding the movement of hydrogen ions in crystals – a key step towards more efficient energy conversion in the hydrogen industry of tomorrow.
As charge carriers, electrons and ions play the leading role in electrochemical energy storage devices and converters such as batteries and fuel cells. Proton...
Scientists from the Excellence Cluster Universe at the Ludwig-Maximilians-Universität Munich have establised "Cosmowebportal", a unique data centre for cosmological simulations located at the Leibniz Supercomputing Centre (LRZ) of the Bavarian Academy of Sciences. The complete results of a series of large hydrodynamical cosmological simulations are available, with data volumes typically exceeding several hundred terabytes. Scientists worldwide can interactively explore these complex simulations via a web interface and directly access the results.
With current telescopes, scientists can observe our Universe’s galaxies and galaxy clusters and their distribution along an invisible cosmic web. From the...
Temperature measurements possible even on the smallest scale / Molecular ruby for use in material sciences, biology, and medicine
Chemists at Johannes Gutenberg University Mainz (JGU) in cooperation with researchers of the German Federal Institute for Materials Research and Testing (BAM)...
19.06.2017 | Event News
13.06.2017 | Event News
13.06.2017 | Event News
26.06.2017 | Life Sciences
26.06.2017 | Physics and Astronomy
26.06.2017 | Information Technology