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uni'wissen 01-2014_ENG

When chromatin takes on its open form, on the other hand, the DNA is freely accessible, and transcription factors can bind more easily to the genetic information. “One of the things epigenetic changes do is to spread this packed chromatin structure out into an open structure or the other way around,” explains Schüle. In a manner of speaking, they can thus switch a gene on or off by packing or unpacking it. One way a structural change can be initiated is when an enzyme – a sub- stance that triggers or accelerates a biochemical reaction or steers it in a certain direction – in- fluences the histone proteins in the nucleosome. “We want to understand the foundations as a basis for developing new therapeutic procedures.” The enzyme Schüle and his team are devoting most of their attention to removes a methyl group from the histone and can thus set off various reactions. Since it docks onto lysin – an amino acid that often sticks out of the histone like an antenna – this enyzme is called lysin-specific demethylase, LSD1 for short. It could be the key to the reliable diagnosis and treatment of prostate cancer. Up until 2004, the general consensus was that when a methyl group is present at one of the histone proteins, it cannot be removed again. Then scientists at Harvard University, USA, showed that enzymes of the class histone-demethylase do precisely this and thus switch off genes. In 2005, Schüle and his team demonstrated in an article in the journal Nature that LSD1 can also do the opposite: “Depending on where LSD1 removes the methyl groups from the chromatin, it can also activate genes.” Wound up into a ball or open: Epigenetic modifications can change the structure of chromatin, the packaging of deoxyribonucleic acid (DNA). Chromatin is made up of so-called histone proteins (red), DNA (blue), and further proteins in the nucleus (yellow). Illustration: Christian Eisenberg 999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999