Epigenetics is defined by heritable changes in gene expression that do not derive from changes in the DNA sequence itself. Epigenetic processes play a central role in a broad spectrum of diseases, such as cardiovascular disease, neurodegenerative disorders and cancer. One of the most prominent epigenetic processes is DNA methylation, where one of the four bases of animal DNA is marked by a methyl group. DNA methylation typically reduces the activity of surrounding genes.
A lot is known about how methyl marks are put onto the DNA, but how they are removed—a process called DNA demethylation— and, thus, how genes are reactivated is still not well understood. In their recent study, published in Nature Structural and Molecular Biology, IMB scientists have identified two proteins, Neil1 and Neil2 that are important for the demethylation of DNA.
“These proteins are a missing link in the chain of events that explain how DNA can be efficiently demethylated,” said Lars Schomacher, first author on the paper.
Intriguingly, DNA demethylation has been shown to involve proteins of the DNA repair machinery. Thus epigenetic gene regulation and genome maintenance are linked. Schomacher and his colleagues identified in Neil1 and Neil2 two more repair factors that not only protect the DNA’s integrity but are also involved in DNA demethylation. The researchers showed that the role of Neils is to boost the activity of another protein, Tdg, which is known to be of central importance for DNA demethylation.
Both the Neils and Tdg are essential proteins for survival and development. Schomacher et al. carried out experiments where they removed either one of these proteins in very early frog embryos. They found that the embryos had severe problems developing and died before reaching adulthood.
Failure in setting and resetting methyl marks on DNA is involved in developmental abnormalities and cancer, where cells forget what type they are and start to divide uncontrollably. Understanding which proteins are responsible for DNA demethylation will help us to understand more about such disease processes, and may provide new approaches to develop treatments for them.
Schomacher L*, Han D*, Musheev MU*, Arab K, Kienhöfer S, von Seggern A and Niehrs C (2016). Neil DNA glycosylases promote substrate turnover by Tdg during DNA demethylation. Nature Struct Mol Biol, DOI: 10.1038/nsmb.3151 [Epub ahead of print]. (* indicates equal contribution)
Further information about research in the Niehrs group can be found at www.imb.de/niehrs.
About the Institute of Molecular Biology gGmbH
The Institute of Molecular Biology gGmbH (IMB) is a centre of excellence in the life sciences that was established in 2011 on the campus of Johannes Gutenberg University Mainz (JGU). Research at IMB concentrates on three cutting-edge areas: epigenetics, developmental biology, and genome stability. The institute is a prime example of a successful collaboration between public authorities and a private foundation. The Boehringer Ingelheim Foundation has dedicated 100 million euros for a period of ten years to cover the operating costs for research at IMB, while the state of Rhineland-Palatinate provided approximately 50 million euros for the construction of a state-of-the-art building. For more information about IMB, please visit: www.imb.de.
About the Boehringer Ingelheim Foundation
The Boehringer Ingelheim Foundation is an independent, non-profit organisation committed to the promotion of the medical, biological, chemical and pharmaceutical sciences. It was established in 1977 by Hubertus Liebrecht (1931-1991), a member of the shareholder family of the company Boehringer Ingelheim. With the PLUS 3 Perspectives Programme and the Exploration Grants, the foundation supports independent group leaders. It also endows the internationally renowned Heinrich Wieland Prize as well as awards for up-and-coming scientists. In addition, the foundation pledged to donate 100 million euros to finance the scientific running of the IMB at Johannes Gutenberg University Mainz for ten years. In 2013, the Boehringer Ingelheim Foundation donated a further 50 million euros to Johannes Gutenberg University Mainz. www.boehringer-ingelheim-stiftung.de.
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