Chromatin-mediated Response to Stimuli
Daniel L. Vera, Lauren A. Cole, Benjamin Hoffman and Jonathan H. Dennis
from: Epigenetics: Current Research and Emerging Trends (Edited by: Brian P. Chadwick). Caister Academic Press, U.K. (2015) Pages: 125-132.
Abstract
In 1950, Edgar and Eileen Stedman hypothesized for the first time that "one of [histones'] physiological functions is to act as gene suppressors". This hypothesis implied that histones may block access to the underlying DNA sequence rendering it functionally unavailable. Sixty-four years later, the expectations of this statement remain unfulfilled. Indeed, cells with differing physiologies display unique gene expression patterns, specific DNA methylation patterns, and different histone post translational modifications. The scientific community had anticipated that cells with different physiologies would also have strikingly different nucleosome distributions; however this has not been the case. Cells with different physiologies have remarkably similar nucleosome distributions. Recently, it has been observed that nucleosome distributions do indeed change in a widespread manner in response to stimulus. This event had not been previously observed, as nucleosome redistributions are transient, returning to their basal positions later in the response. Additionally, a new set of nucleosome mapping experiments have led to the observation that nucleosomes exhibit differential sensitivity to nuclease. These results indicate that these fragile nucleosomes may be targets for regulatory factor binding. The discovery of the widespread but transient nature of nucleosome remodeling combined with the observation that basal nucleosome positions exhibit differential sensitivity to nuclease, has allowed for the development of a new model of a role for chromatin in genome regulation read more ...
