Epigenetic Significance of Chromatin Organization During Cellular Aging and Organismal Lifespan

Aging is a developmental process that occurs through epigenetic reprogramming that involves nine hallmark characteristics, most notably genomic instability. During physiological development, chromatin is modified, reorganized, and de-compacted in order for DNA to be transcribed, replicated, and repaired. The most prominent histone modifications include acetylation, methylation, ubiquitylation, ADP-ribosylation, phosphorylation, and sumoylation. Younger cells/tissues are characterized by greater global methylation. Global DNA demethylation in aging occurs mainly at repetitive DNA elements and in genome regions with facultative heterochromatin, which leads to overall deheterochromatinization of the genome.