This release is available in German.
All cells perform certain basic functions. Each must selectively transcribe parts of the DNA that makes up its genome into RNAs that specify the structure of proteins. The set of proteins synthesized by a cell in turn determines its structure and behaviour, and enables it to survive and reproduce. So it is crucial that the appropriate stretches of DNA are transcribed in each cell type. In today's issue of the journal Nature, a team of researchers at the Gene Center of Ludwig-Maximilians-Universitt (LMU) in Munich, led by Professor Patrick Cramer, provides the first detailed description of how the RNA polymerase II initiates gene transcription. "The findings led us to propose a model of the whole complicated process of transcription initiation," says Cramer. "This operation is of crucial importance in all organisms, because it determines which genes are expressed, and when. Our work thus represents a milestone in the quest to understand gene regulation."
Cell types such as liver cells and nerve cells differ from one another because they make distinct sets of proteins. Therefore, gene transcription and protein synthesis must be carried out with great precision. This requires the use of complicated assemblies made up of many different proteins, often referred to as molecular machines. The basic structure of RNA polymerase II, the protein complex that transcribes genes encoding proteins in multicellular organisms, was worked out some years ago, but this structure could not explain how the initial steps in transcription take place.
Signals encoded in the DNA sequence tell RNA polymerase II where to start and stop transcription. The regions in which transcription begins are called promoters. In many genes, the promoter region is marked by a short DNA sequence called the TATA box. The actual transcriptio
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