Metabolism of caffeine to nucleic acid precursors in mammalian cells

Goth, Regine; Cleaver, James E.

doi:10.1016/0027-5107(76)90025-7

Cited by 42 publications

(11 citation statements)

References 21 publications

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“…These results suggested that ATR-mediated signaling pathways are involved in the recruitment of pol . Caffeine has been shown to inhibit other protein kinases as well as ATR and have other nonspecific effects (26,27). Therefore, to confirm that the observed effects of caffeine on relocation of pol were mediated by ATR, specific siRNA was used to suppress ATR protein expression (Fig.…”

Section: Resultsmentioning

confidence: 99%

Human DNA polymerase η activity and translocation is regulated by phosphorylation

Chen

Cleaver

Hatahet

et al. 2008

Proc. Natl. Acad. Sci. U.S.A.

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Human DNA polymerase (pol ) can replicate across UV-induced pyrimidine dimers, and defects in the gene encoding pol result in a syndrome called xeroderma pigmentosum variant (XP-V). XP-V patients are prone to the development of cancer in sun-exposed areas, and cells derived from XP-V patients demonstrate increased sensitivity to UV radiation and a higher mutation rate compared with wild-type cells. pol has been shown to replicate across a wide spectrum of DNA lesions introduced by environmental or chemotherapeutic agents, or during nucleotide starvation, suggesting that the biological roles for pol are not limited to repair of UV-damaged DNA. The high error rate of pol requires that its intracellular activity be tightly regulated. Here, we show that the phosphorylation of pol increased after UV irradiation, and that treatment with caffeine, siRNA against ATR, or an inhibitor of PKC (calphostin C), reduced the accumulation of pol at stalled replication forks after UV irradiation or treatment with cisplatin and gemcitabine. Site-specific mutagenesis (S587A and T617A) of pol at two putative PKC phosphorylation sites located in the proteinprotein interaction domain prevented nuclear foci formation induced by UV irradiation or treatment with gemcitabine/cisplatin. In addition, XP-V cell lines stably expressing either the S587A or T617A mutant form of pol were more sensitive to UV radiation and gemcitabine/cisplatin than control cells expressing wild-type pol . These results suggest that phosphorylation is one mechanism by which the cellular activity of pol is regulated. xeroderma pigmentosum variant ͉ lesion bypass X eroderma pigmentosum (XP) is an autosomal recessive condition characterized by premature skin aging, pigmentary changes, photosensitivity, and malignant tumor development. The manifestations associated with XP are because of a cellular hypersensitivity to UV radiation resulting from defects in any one of a number of genes encoding nucleotide excision repair (XP-A to -G) proteins (1, 2). Human DNA polymerase (pol ) is an important enzyme that replicates across pyrimidine dimers introduced by UV radiation (3), and defects in the gene encoding pol result in xeroderma pigmentosum variant (XP-V) syndrome (3, 4). Similar to patients with other forms of XP, patients with XP-V are highly sensitive to UV radiation and prone to the development of skin cancer (5). Furthermore, cells derived from XP-V patients exhibit a higher mutation rate (6) than the wild-type cells. In addition to pyrimidine dimers, pol has been shown to replicate across 8-hydroxyurea-induced lesions, O 6 -methylguanine, and cisplatin cross-linked intrastrand GG sites (7). Recently, we have shown that pol incorporates, extends, and bypasses chemotherapeutic nucleoside analogs AraC and gemcitabine (8). pol is also involved in Ig hypermutation (9), strand invasion during homologous recombination (10), and replication during nucleotide starvation (11). These studies suggest that in addition to its roles in the protection of cells from DNA damage, p...

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Section: Resultsmentioning

confidence: 99%

Human DNA polymerase η activity and translocation is regulated by phosphorylation

Chen

Cleaver

Hatahet

et al. 2008

Proc. Natl. Acad. Sci. U.S.A.

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“…In mammalian cells, caffeine was shown to block the activity of phosphodiesterase, which functions in metabolism of cyclic AMP, a critical factor in phosphorylation signaling cascade. 15 Since plants adopt a similar signaling system, 16 identification of signaling factors that are affected in transgenic lines is a powerful approach to understand the molecular aspects. resistance against B. cinerea (Fig.…”

Section: ©2 0 1 1 L a N D E S B I O S C I E N C E D O N O T D I S Tmentioning

confidence: 99%

Simultaneous activation of salicylate production and fungal resistance in transgenic Chrysanthemum producing caffeine

Kim

Lim

Yoda

et al. 2011

Plant Signaling & Behavior

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“…17,24,25 In the cell, DNA synthesis can proceed through 2 distinct pathways depending on the disposable intracellular pools: a de novo pathway synthesizing nucleic acids from precursors and a salvage pathway utilizing preformed purine rings such as xanthine. 25 The demethylation of caffeine results in a consequent accumulation of xanthine, this could account for the inhibition of cell proliferation by caffeine.In the present study we confirm the results previously obtained with NHFs. 13 This weakens the concept of an override of the irradiation induced G2/M block caused by caffeine which may result from a misinterpretation of the cell cycle kinetic delay due to the inhibition of cell proliferation.…”

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confidence: 99%

“…It is able to transfer methyl groups to thymidine and also to adenine and to guanine in de novo synthesis. 17,24,25 In the cell, DNA synthesis can proceed through 2 distinct pathways depending on the disposable intracellular pools: a de novo pathway synthesizing nucleic acids from precursors and a salvage pathway utilizing preformed purine rings such as xanthine. 25 The demethylation of caffeine results in a consequent accumulation of xanthine, this could account for the inhibition of cell proliferation by caffeine.…”

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confidence: 99%

Caffeine and the G2/M block override: A concept resulting from a misleading cell kinetic delay, independent of functional p53

et al. 2001

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In the literature the sensitization of DNA to radiationinduced damage by caffeine has been attributed to an override of the G2/M block. This process was supposed to involve the tumor suppressor gene p53 as it was described that p53 negative cells were more sensitive to checkpoint inhibition by caffeine than the wildtype phenotype. We have recently shown that caffeine does not cause an override of the G2/M block induced by radiation in normal human fibroblasts. We demonstrate here that this also applies to a human transformed cell line, the thyroid carcinoma K1, when submitted to ␥-rays irradiation. Within 9 hr after irradiation over 70% of the cells accumulated in the G2/M phase. This block persisted at 16 hr. In caffeine containing cultures the percentage of cells attaining the G2/M phase was reduced by over 30% at 16 hr. This was reflected in an accumulation of the cells in G1 phase and an inhibition of the S phase traverse. Cell cycle analyses from further time points combined with cell proliferation measurements confirmed these data. These results were independent of p53 status as experiments performed with variant K1 cell lines having defective p53 functions, led to similar conclusions. In addition, caffeine restored a G1 delay after irradiation in the cell lines with abrogated p53 functions. The effects of caffeine undeniably cumulate with damages induced by irradiation but probably by inhibiting DNA repair mechanisms or by intervening with purine and pyrimidine metabolisms and not by causing a G2/M block override. © 2001 Wiley-Liss, Inc. Key words: K1; p53 status; ␥ radiation; cell cycle checkpoints; caffeine; G2/M overrideThe tumor suppressor gene p53 is mutated in over 50% of human tumors. 1 It has been defined as the "guardian of the genome" 2 and represents the keystone between the control of cell proliferation and the maintenance of genetic integrity. 3 Among a wide range of functions, 4 p53 intervenes in cell cycle control at checkpoints G1/S and possibly at the G2/M. 3,5 For several years, it has been emphasized that caffeine causes the override of the G2/M checkpoint, thus leaving the cells less time to repair drug and radiation induced damages. 6 -12 In addition, several authors have demonstrated that this property of caffeine was correlated with the p53 status of the cells i.e., p53 Ϫ/Ϫ cells were more sensitive to caffeine-induced radiosensitization than p53 ϩ/ϩ cells. 9 -11 By using normal human fibroblasts (NHFs), we have recently shown that the apparent override of the radiation induced G2 block in the presence of caffeine is in fact due to a slowing down of the cell cycle. The presence of caffeine retards the entry of cells into the G2/M phase after UVc or ␥-ray radiations and perfectly mimics a G2/M override if the cell proliferation kinetics are ignored. 13 Similar experiments performed in our laboratory with the Chinese Hamster Ovary (CHO-K1) cell line which contains a missense mutation for p53 at codon 211 (Thr3 Lys) 14,15 led to identical conclusions (unpublished results).To investi...

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Metabolism of caffeine to nucleic acid precursors in mammalian cells

Cited by 42 publications

References 21 publications

Human DNA polymerase η activity and translocation is regulated by phosphorylation

Human DNA polymerase η activity and translocation is regulated by phosphorylation

Simultaneous activation of salicylate production and fungal resistance in transgenic Chrysanthemum producing caffeine

Caffeine and the G2/M block override: A concept resulting from a misleading cell kinetic delay, independent of functional p53

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