What is not histone protien its function

Genes aren't everything

How modified histone proteins regulate genes

Until the 1990s, scientists assumed that histones, the most common proteins in the cell nucleus, were only responsible for organizing and stabilizing DNA. But it is now clear that they can intervene in the regulation of genes in a variety of ways. Depending on the change in their basic structure, they activate or inhibit the reading of genes. Together with colleagues from Dresden and the Netherlands, researchers from the Max Planck Institute for Biochemistry (MPIB) in Martinsried near Munich have now identified additional interaction partners in this process. Only the latest methods of mass spectrometry made this possible. (Cell, September 17, 2010)

The human genetic material (DNA) is not in a disordered manner in the cell. Like coils, the two-meter-long molecule is wrapped around special proteins (histones) so that it fits into the cell nucleus with a diameter of only 0.006 millimeters. Researchers call the complex of DNA and proteins packaged in this way chromatin. However, histones not only form the framework of chromatin, but also play an essential role in deciding which genes are read and translated into proteins and which are not. Although all cells in an organism have the same genes, these are read differently and different cell types are created, each with a different protein composition. The science that deals with this phenomenon is called epigenetics. Errors can lead to disorders in the development of an embryo or to diseases such as cancer.

Although histones play such an important role in gene regulation, the exact mechanism is not yet fully understood. Changes in the structure of the histones play an important role: by adding chemical groups, the histones are modified in such a way that they can be distinguished from unchanged histones. In this way, they can perform a specific function at this special point in the genome.

One of the most common modifications is methylation, which causes proteins to continue to bind to the modified histones. In this way, they can make reading a gene easier or else prevent it. Although this had long been known, the identity of the proteins involved was largely unknown. Scientists working with Matthias Mann, head of the Proteomics and Signal Transduction Research Department at the Max Planck Institute for Biochemistry, have now been able to identify proteins for the five most important methylations that bind to the modified histone proteins. "Until now it was extremely difficult to determine these proteins," explains Christian Eberl, doctoral student at the MPIB. "Only the newest techniques of quantitative mass spectrometry, which were developed in Matthias Mann's department, made this possible."

The scientists' results form the basis for further experiments which should bring to light exactly what role the proteins that bind to the histones play. "With our work we have taken another big step towards elucidating the multiple mechanisms through which histone modifications influence gene regulation," said Eberl. Since changes in the histones and proteins that bind to histones also play a role in some cancers, the results could, in the long term, lead to a better understanding of these diseases and thus to new therapeutic approaches, the researchers hope.