Abstract
The ability of caffeine to reverse cell cycle checkpoint function and enhance genotoxicity after DNA damage was examined in telomerase-expressing human fibroblasts. Caffeine reversed the ATM-dependent S and G2 checkpoint responses to DNA damage induced by ionizing radiation (IR), as well as the ATR- and Chk1-dependent S checkpoint response to ultraviolet radiation (UVC). Remarkably, under conditions in which IR-induced G2 delay was reversed by caffeine, IR-induced G1 arrest was not. Incubation in caffeine did not increase the percentage of cells entering the S phase 6-8h after irradiation; ATM-dependent phosphorylation of p53 and transactivation of p21(Cip1/Waf1) post-IR were resistant to caffeine. Caffeine alone induced a concentration- and time-dependent inhibition of DNA synthesis. It inhibited the entry of human fibroblasts into S phase by 70-80% regardless of the presence or absence of wildtype ATM or p53. Caffeine also enhanced the inhibition of cell proliferation induced by UVC in XP variant fibroblasts. This effect was reversed by expression of DNA polymerase eta, indicating that translesion synthesis of UVC-induced pyrimidine dimers by DNA pol eta protects human fibroblasts against UVC genotoxic effects even when other DNA repair functions are compromised by caffeine.
Publication types
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Ataxia Telangiectasia Mutated Proteins
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Caffeine / pharmacology*
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Cell Cycle / drug effects*
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Cell Cycle / physiology
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Cell Cycle / radiation effects
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Cell Cycle Proteins
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Cell Line
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Central Nervous System Stimulants / pharmacology*
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Checkpoint Kinase 1
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Cyclin-Dependent Kinase Inhibitor p21
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Cyclins / metabolism
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DNA / drug effects*
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DNA / genetics
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DNA / radiation effects
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DNA Damage
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DNA Repair
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DNA Replication
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DNA-Binding Proteins
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DNA-Directed DNA Polymerase / metabolism
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Fibroblasts / drug effects*
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Fibroblasts / metabolism
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Fibroblasts / radiation effects
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Humans
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Leucine Zippers
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Phosphorylation
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Protein Kinases / metabolism
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Protein Serine-Threonine Kinases / metabolism
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Signal Transduction / physiology*
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Tumor Suppressor Protein p53 / metabolism
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Tumor Suppressor Proteins
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Ultraviolet Rays
Substances
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CDKN1A protein, human
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Cell Cycle Proteins
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Central Nervous System Stimulants
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Cyclin-Dependent Kinase Inhibitor p21
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Cyclins
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DNA-Binding Proteins
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Tumor Suppressor Protein p53
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Tumor Suppressor Proteins
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Caffeine
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DNA
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Protein Kinases
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ATM protein, human
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Ataxia Telangiectasia Mutated Proteins
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CHEK1 protein, human
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Checkpoint Kinase 1
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Protein Serine-Threonine Kinases
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DNA-Directed DNA Polymerase
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Rad30 protein