On the activity and fidelity of chromatin‐associated hepatic DNA polymerase‐β in aging murine species of different life spans

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Abstract
Activity and accuracy of chromatin‐directed DNA replication have been compared in young and aged Mus musculus and Peromyscus leucopus, two murine species with contrasting maximum lifespans. Chromatin isolated from livers of mature adults of both species copied efficiently exogenous DNA templates using predominantly DNA polymerase‐β. The DNA synthetic activity of liver chromatin remained constant in both species throughout their lifetimes. The fidelity of chromatin‐directed poly [d(A‐T)] synthesis was similar for the comparatively short‐lived M. musculus and the relatively long‐lived P. leucopus and remained unaltered in old animals. The fidelity of poly [d(A‐T)] copying catalyzed by DNA polymerase‐β dissociated from liver chromatin was comparable to that of the chromatin‐directed synthesis. The dissociated enzymes did not exhibit diminished fidelity of poly [d(A‐T)] synthesis with age. In all ages of both species examined, the murine liver DNA polymerase‐β, both chromatin‐associated and solubilized, exhibited high error frequencies; approximately one dGMP was incorporated for every 500–1,000 complementary nucleotides polymerized. The relationship of these results to the accuracy of DNA replication and repair as a determinant of aging is considered.