From PLos Biology, a very accessible look at what we know about aging and accelerated aging conditions in terms of change in the cell nucleus. "The cell nucleus in higher organisms is now recognized as a complex, highly organized repository of an individual's genetic information. ... The first hint to a surprising connection between nuclear architecture and aging came from yeast, when Leonard Guarente and colleagues found that a protein, Sir4, whose mutation results in extension of life span, localizes to the nucleolus, one of the most prominent subcompartments of the cell nucleus. The link between aging and nuclear organization was further strengthened by the observation that the localization of the protein and the morphology of the nucleolus itself changed as yeast cells aged."