Fibromodulin gene transcription is induced by ultraviolet irradiation, and its regulation is impaired in senescent human fibroblasts.
Cells undergoing replicative senescence display an altered pattern of gene expression. Senescent fibroblasts show significant changes in the expression of mRNAs encoding extracellular matrix-remodeling proteins; among these mRNAs, the mRNA encoding fibromodulin is highly decreased in these cells. To understand the molecular basis of this phenomenon, we explored the regulatory mechanisms of the human fibromodulin gene. We found that fibromodulin gene promoter contains a cis-element, crucial for its basal expression, that forms a DNA-protein complex when exposed to nuclear extracts from exponentially growing human fibroblasts and not to extracts from cells undergoing senescence by repeated in vitro passages or by mild oxidative stress. The purification of this complex showed that it contains the damage-specific DNA-binding protein DDB-1. The latter is known to be induced by UV irradiation; therefore we checked whether fibromodulin gene promoter is regulated upon the exposure of the cells to UV rays. The results showed that, in exponentially growing fibroblasts, the promoter efficiency is increased by UV irradiation and the DDB-1-containing complex is robustly enriched in cells exposed to UV light. Accordingly, in these experimental conditions the endogenous fibromodulin mRNA accumulates to very high levels. On the contrary, senescent cells did not show any activation of the fibromodulin gene promoter, any induction of the DDB-1-containing complex, or any accumulation of fibromodulin mRNA. These phenomena are accompanied in senescent cells by a decrease of the UV-damaged DNA binding activity.
Dipartimento di Biochimica e Biotecnologie Mediche, Università di Napoli Federico II, CEINGE Biotecnologie avanzate, 80131 Napoli, Italy.
Maria Assunta
MA
Bevilacqua
Barbara
B
Iovine
Nicola
N
Zambrano
Chiara
C
D'Ambrosio
Andrea
A
Scaloni
Tommaso
T
Russo
Filiberto
F
Cimino
D002460:Cell Line; D016922:Cellular Senescence / Q000502:physiology*; D004247:DNA / Q000378:metabolism / Q000528:radiation effects; D004249:DNA Damage; D004268:DNA-Binding Proteins / Q000378:metabolism; D016326:Extracellular Matrix Proteins / Q000096:biosynthesis / Q000235:genetics* / Q000528:radiation effects*; D005347:Fibroblasts / Q000473:pathology* / Q000502:physiology / Q000528:radiation effects*; D000071235:Fibromodulin; D005786:Gene Expression Regulation / Q000528:radiation effects; D006367:HeLa Cells; D006801:Humans; D011401:Promoter Regions, Genetic / Q000528:radiation effects; D011509:Proteoglycans / Q000096:biosynthesis / Q000235:genetics* / Q000528:radiation effects*; D014158:Transcription, Genetic / Q000528:radiation effects*; D014466:Ultraviolet Rays
C091435:DDB1 protein, human; D004268:DNA-Binding Proteins; D016326:Extracellular Matrix Proteins; C000604330:FMOD protein, human; D011509:Proteoglycans; D000071235:Fibromodulin; D004247:DNA