Histones are proteins that are found in the cell's nucleus, where they are present in complexes with DNA and are presumed to play a regulatory role in all processes that take place on the DNA. These processes include transcription, namely RNA synthesis, and the duplication of DNA during cell division. Until now, the function of the individual histones in the various processes could only be determined indirectly. Molecular biologists Konrad Basler and Martina Hdl from the University of Zurich for the first time directly studied the function of two histones and one histone modification with surprising results: Viable and fertile organisms develop in the absence of the histone known as H3.3. Additionally a particular histone modification was believed to be crucial for the activation of gene transcription. However, the researchers were able to demonstrate that this is also not the case. The established models for the role and function of histones and their modifications during the transcription and cell-division need to be revised.
Fertile fruit flies despite lack of histone H3.3
For their study, Basler and his postdoctoral student Hdl used the fruit fly Drosophila melanogaster, the genome of which has been fully decoded. In an initial experiment, the scientists switched the two histone variants H3.2 and H3.3 in the cells. In normal (i.e. non-manipulated) cells, histone H3.2 is only expressed in one specific phase of the cell cycle, the so-called S phase. Histone H3.3, however, is always expressed. Consequently, it was assumed that histone H3.3 plays a key role in transcription, especially in reading genes. Thus, the general consensus was that RNA synthesis would be restricted in the absence of histone H3.3. "In our experiment, under lab conditions viable and fertile fruit flies could develop from cells that do not have any H3.3," explains Hdl, summing up the result that turns the previous understanding on its head. "Organisms also
|Contact: Martina Hdl|
University of Zurich