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An organism's genome contains all of the information necessary for each of its cells and tissues to develop and function properly. Written in DNA, each individual gene encodes for something, whether it is a structural protein that helps define a tissue's shape, an enzyme that catalyzes the chemical reactions of life, or a signaling protein that cells use to communicate.
Like a dimmer light switch, each gene can be turned on (expressed) strongly or weakly, or turned off entirely. Individual cells have different gene expression profiles, which enables them to have the different functions that make them part of different tissues. For example, an immune cell expresses proteins that allow it to recognize harmful intruders, while a neuron expresses proteins that enable it to pass nerve signals to its neighbors.
Ability - Cell - Genes - Silent - Cell
The ability for a cell to repress genes, keeping them silent, is therefore critical. In the cell DNA is wound tightly around spools made of proteins, like thread wrapped around a bobbin, and this combined DNA-protein structure is called chromatin. Different genes have distinct chromatin structures, and these structures play an important role in regulating their expression. How genes that need to be silenced are identified and packaged in repressive chromatin structures is not well understood. Now, Caltech biologists have characterized molecular mechanisms that cells can use to silence their own genes.
The research is a collaboration between the laboratories of Professor of Biology Alexei Aravin and Research Professor Katalin Fejes Toth. It is described in two new papers appearing in the journal Molecular Cell.
The first paper...
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