Chromatin Remodeling And TonEBP-Dependent Gene Transcription

Eukaryotic cell membrane is permeable to water. When a cell experiences hypertonic stress, water is withdrawn from the cell along the osmotic gradient and Na+, Cl-, and K+ ions are accumulated within the cell, which results in cell shrinkage. This condition is detrimental because high ionic strength destabilizes proteins and compromises cellular functions. Cells respond to this situation by replacing these ions with organic osmolytes, which is able to resume osmotic equilibrium and preserve cell volume without perturbing macromolecular structure and function. A series of experiments have demonstrated that extracellular hypertonicity induces a set of osmocompensatory genes transcription, leading to the accumulation of gene products and osmolytes within the cells. TonEBP (Tonicity Element Binding Protein), has been identified as a transcription factor responsible for the hypertonic induction of osmocompensatory genes. The chromatin environment of a gene has a major influence on its transcription efficiency. The activation and repression of genes have been associated with alterations in chromatin structure. Several general mechanisms for altering...