What role does chromatin play in gene expression?

Chromatin is a highly structured complex in which DNA is stored. Epigenetic processes regulate gene expression by altering the structure of chromatin. Actively transcribed genes are found in chromatin regions that are accessible, whereas transcriptionally silent genes are found in inaccessible chromatin regions. Whether it is a blessing or a curse, chromatin adds an extra layer of control over gene expression. This control is exercised via a slew of chemical modifications to histones and DNA known as epigenetic marks, which alter chromatin structure and provide specific recognition sites for regulatory factors. In response to environmental stimuli, the epigenome undergoes biochemical changes, which result in chromatin structure remodeling. The term "chromatin remodeling" primarily refers to the ATP-dependent process of genomic transformation by nucleosome-shifting enzymes such as the SWI/SNF complex. Epigenetics heavily relies on chromatin remodeling. Epigenetic modifi