Dr. Jan-Michael Peters and his team at the Research Institute of Molecular Pathology (IMP) in Vienna, Austria, have found that the structure of chromosomes is supported by a kind of molecular skeleton, made of cohesin. This discovery was reported online on August 25, 2013 in Nature. Every single cell in the human body contains an entire copy of the genetic blueprint, the DNA. Its total length is about 3.5 meters and all of it has to fit into the cell’s nucleus, just one-hundredth of a millimeter in diameter. Blown up in proportion, this would equal the task of squeezing a 150-km-long string into a soccer ball. Just how the cell manages to wrap up its DNA so tightly is still poorly understood. One way of compacting DNA is achieved by coiling it tightly around histone proteins. This mechanism has been studied in detail and is the focus of an entire discipline, epigenetics. However, simple organisms such as bacteria have to manage their DNA packaging without histones, and even in human cells, histones probably cannot do the job on their own. In its Nature article, Dr. Peters’ IMP research team in Vienna presents evidence for an additional mechanism involved in structuring DNA. IMP Managing Director Dr. Peters and his research group discovered that a protein complex named cohesin has a stabilizing effect on DNA. In evolutionary terms, cohesin is very old and its structure has hardly changed over billions of years. It was present long before histones and might therefore provide an ancient mechanism in shaping DNA. Cell biologists are already familiar with cohesin and its role in cell division. The protein complex is essential for the correct distribution of chromosomes to daughter cells.
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