There are more than 300 different cell types in human body, such as neurons, muscle cells or blood cells. In order to maintain the integrity of human body cells need to communicate between each other using a specific "language". The words of such a language comprise whole range of chemical molecules throughout which the message is passed from outside the cell into the cell body. The words are further connected into simple sentences that we call signalling pathways. Consequently cells can understand what is happening in their environment and respond appropriately (f.e. by cell division or differentiation).
This type of language is extremely important for the life of any cell and, to large extend, it is universal across animal species. Therefore research of simple organisms such as Drosophila makes it possible to understand processes that occur also in higher organisms including human. The aim of our research is to understand a widely used signalling pathway called the Notch pathway. It is very well conserved across species and plays a critical role in wide diversity of developmental processes as well as in adult organism and in cancer. There are three key players in this pathway: i) a sensor in the membrane of signal receiving cell called Notch, ii) its ligands in the membrane of the cell sending cell and iii) protein in the nucleus of the signal receiving cells that binds DNA and serves as the signal interpreter. It is called Supressor of Hairless (Su(H)). As a response to Notch pathway activation Su(H) switches on the expression of many genes in the nucleus. We have analysed the interactions between Su(H) and DNA in Drosophila cultured cells and found out that they are very dynamic. Our data challenge the prevailing model of Notch pathway activation and propose a new layer of regulation in nuclear signalling. Krejci A and Bray S: Notch activation stimulates transient and selective binding of Su(H)/CSL to target enhancers. Genes Dev. 2007 Jun 1;21(11):1322-7.