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Accelerated methylation of ribosomal RNA genes during the cellular senescence of Werner syndrome fibroblasts
Author(s) -
Machwe Amrita,
Orren David K.,
Bohr Vilhelm A.
Publication year - 2000
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fj.99-0926com
Subject(s) - senescence , biology , methylation , ribosomal rna , dna methylation , microbiology and biotechnology , gene , ribosomal dna , fibroblast , rna , gene expression , genetics , in vitro , phylogenetics
Ribosomal DNA (rDNA) metabolism has been implicated in cellular and organismal aging. The role of rDNA in premature and normal human aging was investigated by measuring rDNA gene copy number, the level of rDNA methylation, and rRNA expression during the in vitro senescence of primary fibroblasts from normal (young and old) donors and from Werner syndrome (WS) patients. In comparison to their normal counterparts, WS fibroblasts grew slowly and reached senescence after fewer doublings. The rDNA copy number did not change significantly throughout the life span of both normal and WS fibroblasts. However, in senescent WS and normal old fibroblasts, we detected rDNA species with unusually slow electrophoretic mobility. Cellular aging in Saccharomyces cerevisiae is accompanied by the formation and accumulation of rDNA circles. Our analysis revealed that the rDNA species observed in this study were longer, linear rDNA molecules attributable to the inhibition of Eco RI cleavage by methylation. Furthermore, isoschizomeric restriction analysis confirmed that in vitro senescence of fibroblasts is accompanied by significant increases in cytosine methylation within rDNA genes. This increased methylation is maximal during the abbreviated life span of WS fibroblasts. Despite increased methylation of rDNA in senescent cells, the steadystate levels of 28S rRNA remained constant over the life span of both normal and WS fibroblasts.— Machwe, A., Orren, D. K., Bohr, V. A. Accelerated methylation of ribosomal RNA genes during the cellular senescence of Werner syndrome fibroblasts. FASEB J. 14, 1715–1724 (2000)