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. Author manuscript; available in PMC: 2009 Jun 9.
Published in final edited form as: Exp Cell Res. 2008 Mar 12;314(9):1909–1917. doi: 10.1016/j.yexcr.2008.02.023

Figure 1. A model depicting the proposed impact of heterochromatin on longevity of mammals.

Figure 1

Considerable evidence, discussed in the text, supports the idea that heterochromatin redistributes in cells during cellular and organismal aging. The primary purpose of this redistribution might be to extend longevity by promoting tumor suppression (green arrows). According to the idea of antagonistic pleiotropy, this will also lead to decreased renewal of adult tissue stem cells and renewable tissues, and consequently tissue aging (blue arrows). Stochastic errors in the redistribution of heterochromatin (e.g. excessive spreading of heterochromatin along chromosomes) might lead to erroneous silencing of other genes, e.g. tumor suppressor genes. In this case, redistributed heterochromatin will tend to decrease longevity (thin black lines). Actual organismal longevity will ultimately be determined by the balance between these competing processes.