Biomedical subjects

E Sage

Publications and source records attributed to E Sage.

At least 19 recordsLinked to original sources

PubMed2005

UVA radiation is highly mutagenic in cells that are unable to repair 7,8-dihydro-8-oxoguanine in Saccharomyces cerevisiae.

UVA (320-400 nm) radiation constitutes >90% of the environmentally relevant solar UV radiation, and it has been proposed to have a role in skin cancer and aging. Because of the popularity of UVA tanning beds and prolonged periods of sunbathing, the potential deleterious effect of UVA has emerged as a source of concern for public health. Although generally accepted, the impact of DNA damage on the cytotoxic, mutagenic, and carcinogenic effect of UVA radiation remains unclear. In the present study, we investigated the sensitivity of a panel of yeast mutants affected in the processing of DNA damage to the lethal and mutagenic effect of UVA radiation. The data show that none of the major DNA repair pathways, such as base excision repair, nucleotide excision repair, homologous recombination, and postreplication repair, efficiently protect yeast from the lethal action of UVA radiation. In contrast, the results show that the Ogg1 DNA glycosylase efficiently prevents UVA-induced mutagenesis, suggesting the formation of oxidized guanine residues. Furthermore, sequence analysis of UVA-induced canavanine-resistant mutations reveals a bias in favor of GC-->TA events when compared with spontaneous or H(2)O(2)-, UVC-, and gamma-ray- induced canavanine-resistant mutations in the WT strain. Taken together, our data point out a major role of oxidative DNA damage, mostly 7,8-dihydro-8-oxoguanine, in the genotoxicity of UVA radiation in the yeast Saccharomyces cerevisiae. Therefore, the capacity of skin cells to repair 7,8-dihydro-8-oxoguanine may be a key parameter in the mutagenic and carcinogenic effect of UVA radiation in humans.

Aging↗

PubMed2002

Biological effects induced by K photo-ionisation in and near constituent atoms of DNA.

In order to assess the lethal efficiency and other biological effects of inner shell ionisations of constituent atoms of DNA ('K' events), experiments were developed at the LURE synchrotron facility using ultrasoft X rays as a probe of K events. The lethal efficiency of ultrasoft X rays above the carbon K threshold was especially investigated using V79 cells and compared with their efficiency to induce double strand breaks in dry plasmid-DNA. A correlation between the K event efficiencies for these processes is shown. Beams at 340 eV were found to be twice as efficient at killing cells than were beams at 250 eV. In addition, a rough two-fold increase of the relative biological effectiveness for dicentric + ring induction has also been observed between 250 and 340 eV radiations.

Animals↗

PubMed2002

Cell inactivation and double-strand breaks: the role of core ionizations, as probed by ultrasoft X rays.

The large RBE (approximately 7) measured for the killing of Chinese hamster V79 cells by 340 eV ultrasoft X rays, which preferentially ionize the K shell of carbon atoms (Hervé du Penhoat et al., Radiat. Res. 151, 649-658, 1999), was used to investigate the location of sensitive sites for cell inactivation and the physical modes of action of radiation. The enhancement of the RBE above the carbon K-shell edge either may indicate a high intrinsic efficiency of carbon K-shell ionizations (due, for example, to a specific physical or chemical effect) or may be related to the preferential localization of these ionizations on the DNA. The second interpretation would indicate a strong local (within 3 nm) action of K-shell ionizations and consequently the importance of a direct mechanism for radiation lethality (without excluding an action in conjunction with an indirect component). To distinguish between these two hypotheses, the efficiencies of core ionizations in DNA atoms (phosphorus L-shell, carbon K-shell, and oxygen K-shell ionizations) to induce damages were investigated by measuring their capacities to produce DNA double-strand breaks (DSBs). The effect of photoionizations in isolated DNA was studied using pBS plasmids in a partially hydrated state. No enhancement of the efficiency of DSB induction by carbon K-shell ionizations compared to oxygen K-shell ionizations was found, supporting the hypothesis that it is the localization of these carbon K-shell events on DNA which gives to the 340 eV photons their high killing efficiency. In agreement with this interpretation, cell inactivation and DSB induction, which do not appear to be correlated when expressed in terms of yields per unit dose in the sample, exhibit a rather good correlation when expressed in terms of efficiencies per core event in the DNA. These results suggest that core ionizations in DNA, through core-hole relaxation in conjunction with localized effects of spatially correlated secondary and Auger electrons, may be the major critical events for cell inactivation, and that the resulting DSBs (or a constant fraction of these DSBs) may be a major class of unrepairable lesions.

Animals↗

PubMed2001

Hepatic lipase overexpression lowers remnant and LDL levels by a noncatalytic mechanism in LDL receptor-deficient mice.

To address the role of the noncatalytic ligand function of hepatic lipase (HL) in low density lipoprotein (LDL) receptor-mediated lipoprotein metabolism, we characterized transgenic mice lacking the LDL receptor (LDLR) that express either catalytically active (Ldlr(-/-)HL) or inactive (Ldlr(-/-)HL(S145G)) human HL on both chow and high fat diets and compared them with nontransgenic Ldlr(-/-) mice. In mice fed a chow diet, apolipoprotein (apo)B-containing lipoprotein levels were 40-60% lower in Ldlr(-/-)HL and Ldlr(-/-)HL(S145G) mice than in Ldlr(-/-) mice. This decrease was mainly reflected by decreased apoB-48 levels in the Ldlr(-/-)HL mice and by decreased apoB-100 levels in Ldlr(-/-) HL(S145G) mice. These findings indicate that HL can reduce apoB-100-containing lipoproteins through a noncatalytic ligand activity that is independent of the LDLR. Cholesterol enrichment of the apoB-containing lipoproteins induced by feeding Ldlr(-/-)HL and Ldlr(-/-)HL(S145G) mice a cholesterol-enriched high fat (Western) diet resulted in parallel decreases in both apoB-100 and apoB-48 levels, indicating that HL is particularly efficient at reducing cholesterol-enriched apoB-containing lipoproteins through both catalytic and noncatalytic mechanisms. These data suggest that the noncatalytic function of HL provides an alternate clearance pathway for apoB-100- and apoB-48-containing lipoproteins that is independent of the LDLR and that contributes to the clearance of high density lipoproteins.

Animal Feed↗

PubMed2000

Distribution and repair of bipyrimidine photoproducts in solar UV-irradiated mammalian cells. Possible role of Dewar photoproducts in solar mutagenesis.

In order to better understand the relative contribution of the different UV components of sunlight to solar mutagenesis, the distribution of the bipyrimidine photolesions, cyclobutane pyrimidine dimers (CPD), (6-4) photoproducts ((6-4)PP), and their Dewar valence photoisomers (DewarPP) was examined in Chinese hamster ovary cells irradiated with UVC, UVB, or UVA radiation or simulated sunlight. The absolute amount of each type of photoproduct was measured by using a calibrated and sensitive immuno-dot-blot assay. As already established for UVC and UVB, we report the production of CPD by UVA radiation, at a yield in accordance with the DNA absorption spectrum. At biologically relevant doses, DewarPP were more efficiently produced by simulated solar light than by UVB (ratios of DewarPP to (6-4)PP of 1:3 and 1:8, respectively), but were detected neither after UVA nor after UVC radiation. The comparative rates of formation for CPD, (6-4)PP and DewarPP are 1:0.25 for UVC, 1:0. 12:0.014 for UVB, and 1:0.18:0.06 for simulated sunlight. The repair rates of these photoproducts were also studied in nucleotide excision repair-proficient cells irradiated with UVB, UVA radiation, or simulated sunlight. Interestingly, DewarPP were eliminated slowly, inefficiently, and at the same rate as CPD. In contrast, removal of (6-4)PP photoproducts was rapid and completed 24 h after exposure. Altogether, our results indicate that, in addition to CPD and (6-4)PP, DewarPP may play a role in solar cytotoxicity and mutagenesis.

Animals↗

PubMed2000

Heavy ion-induced plasmid DNA damage in aerated or deaerated conditions.

Using the plasmid relaxation assay, the induction of single strand breaks (SSB) and base damages was investigated in air-dried plasmid DNA irradiated under air or under vacuum, with two high LET particles. We first observed that an irradiation with 12C5+ ion produced less of both damages when performed in a vacuum rather than in the presence of air. This could be due to the presence of O2 which increases the primary radicalar effects in the latter case. Another explanation is a difference in the degree of hydration of the DNA molecules. Indeed, under vacuum only the water molecules tightly bound to DNA will persist. In contrast, in the presence of air, the outer hydration shell enhances the amount of hydroxyl radicals available for the radiolytic attack. However, no difference in the SSB induction was observed when DNA was irradiated with 36S16+ ion in the presence of air or under vacuum. This is likely due to the LET effect which partly cancels the production of radicals by recombination and increases the formation of superoxide anions in the track. Similarly, the lower induction of damage by 36S16+ irradiation in comparison with the 12C5+ ion is a consequence of the higher ionizing density for 36S16+ than for 12C5+ ions. Meanwhile, for both ions, base damages are not detected when DNA is irradiated under vacuum, whereas they are as frequent as SSB when irradiation is performed in the presence of air. Altogether, these observations support the idea that SSB and base damage are not formed by the same mechanism.

Air↗

PubMed1999

Wavelength dependence of ultraviolet-induced DNA damage distribution: involvement of direct or indirect mechanisms and possible artefacts.

DNA damage profiles have been established in plasmid DNA using purified DNA repair enzymes and a plasmid relaxation assay, following exposure to UVC, UVB, UVA or simulated sunlight (SSL). Cyclobutane pyrimidine dimers (CPDs) are revealed as T4 endonuclease V-sensitive sites, oxidation products at purine and pyrimidine as Fpg- and Nth-sensitive sites, and abasic sites are detected by Nfo protein from Escherichia coli. CPDs are readily detected after UVA exposure, though produced 10(3) and 10(5) times less efficiently than by UVB or UVC, respectively. We demonstrate that CPDs are induced by UVA radiation and not by contaminating UVB wavelengths. Furthermore, they are produced at doses compatible with human exposure and are likely to contribute to the mutagenic specificity of UVA [E. Sage et al., Proc. Natl. Acad. Sci. USA 93 (1996) 176-180]. Oxidative damage is induced with a linear dose dependence, for each region of the solar spectrum, with the exception of oxidized pyrimidine and abasic sites, which are not detectable after UVB irradiation. The distribution of the different classes of photolesions varies markedly, depending on wavelengths. However, the unexpectedly high yield of oxidative lesions, as compared to CPDs, by UVA and SSL led us to investigate their production mechanism. An artificial formation of hydroxyl radicals is observed, which depends on the material of the sample holder used for UVA irradiation and is specific for long UV wavelengths. Our study sheds light on a possible artefact in the production of oxidative damage by UVA radiation. Meanwhile, after eliminating some potential sources of the artefact ratios of CPDs to oxidized purine of three and five upon irradiation with UVA and SSL, respectively, are still observed, whereas these ratios are about 140 and 200 after UVC and UVB irradiation.

Artifacts↗

PubMed1999

Oxidation of guanine in cellular DNA by solar UV radiation: biological role.

The formation of cyclobutane pyrimidine dimers (CPD) and 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodGuo) was investigated in Chinese hamster ovary cells upon exposure to either UVC, UVB, UVA or simulated sunlight (SSL). Two cell lines were used, namely AT3-2 and UVL9, the latter being deficient in nucleotide excision repair and consequently UV sensitive. For all types of radiation, including UVA, CPD were found to be the predominant lesions quantitatively. At the biologically relevant doses used, UVC, UVB and SSL irradiation yielded 8-oxodGuo at a rather low level, whereas UVA radiation produced relatively higher amounts. The formation of CPD was 10(2) and 10(5) more effective upon UVC than UVB and UVA exposure. These yields of formation followed DNA absorption, even in the UVA range. The calculated relative spectral effectiveness in the production of the two lesions showed that efficient induction of 8-oxodGuo upon UVA irradiation was shifted toward longer wavelengths, in comparison with those for CPD formation, in agreement with a photosensitization mechanism. In addition, after exposure to SSL, about 19% and 20% of 8-oxodGuo were produced between 290-320 nm and 320-340 nm, respectively, whereas CPD were essentially (90%) induced in the UVB region. However, the ratio of CPD to 8-oxodGuo greatly differed from one source of light to the other: it was over 100 for UVB but only a few units for UVA source. The extent of 8-oxodGuo and CPD was also compared to the lethality for the different types of radiation. The involvement of 8-oxodGuo in cell killing by solar UV radiation was clearly ruled out. In addition, our previously reported mutation spectra demonstrated that the contribution of 8-oxodGuo in the overall solar UV mutagenic process is very minor.

Animals↗

PubMed1998

Triple helix-directed psoralen crosslinks are recognized by Uvr(A)BC excinuclease.

Pyrimidine oligonucleotides bind to the major groove of an oligopyrimidine-oligopurine DNA sequence by triple helix formation. A 14-mer oligopyrimidine 3'-psoralen-conjugate (P) and a doubly modified 5'-acridine/3'-psoralen-oligonucleotide (PA) were photo-crosslinked to their target site. The crosslinked complexes were tested regarding their sensitivity to Uvr(A)BC excinuclease/DNA complex formation and excision, and compared to free psoralen crosslinked to the same site (M). An electrophoretic mobility-shift assay showed that the crosslinked triple-helix did not hamper formation of the (A)2B complex under conditions where the third strand was bound to its target. In vitro excision experiments performed on damaged DNA fragments containing crosslinked 5-methoxypsoralen (M-target) confirmed that the psoralen photoadduct was recognized by Uvr(A)BC and that excision occurred at the crosslinked site. The major cleavage reaction took place on the 5'-side of oligopurine strand. The excision was less efficient on the 5'-side of the pyrimidine strand. The 3'-side incision either on the purine or pyrimidine strand was even weaker. With optimal Uvr(A) concentrations, it was observed that the incision reaction on (P)- and (PA)-modified targets was clearly inhibited compared to the (M)-modified target, reflecting an effect of the oligonucleotide on the recognition/excision process. These results demonstrate that a triple helix is efficient in promoting inhibition of Uvr(A)BC excision nuclease activity. These results could account for divergent findings concerning the effects of triple helix-forming oligonucleotides on repair systems and open new perspectives to study DNA repair processes through the use of bi-substituted triple helix-forming oligonucleotides.

Base Sequence↗

PubMed1997

Photoreaction of new psoralen analogs with DNA: sequence and mutation specificity in the Escherichia coli lacZ gene.

New thio- and seleno-analogs of psoralen were synthesized and analyzed for their photoreactivity toward DNA. Using oligonucleotides of defined sequence, we first showed that these derivatives predominantly generated interstrand crosslinks at 5'-TpA sites. We also observed a surprisingly high reactivity of 7H-thiopyrano[3,2-f][1]benzofuran-7-one (PSO[O-S]) with the BamHI and PstI oligomers, giving rise to the formation of crosslinks at 5'-ApT sites and of the thymidine-psoralen-cytosine type. Next, the sequence specificity in the photochemical binding of all the compounds was investigated in two DNA fragments encompassing the lacZ gene of Escherichia coli, using the T4 DNA polymerase sequencing methodology. Resulting maps demonstrated that thio- and seleno-analogs of psoralen preferentially photoreacted with thymine and cytosine residues. The AT-rich sequences proved to be particularly reactive sites as did adjacent thymines, especially at C-surrounding residues. Likewise, photoaddition at cytosines in CA/AC context was observed. It was highly significant that all of the derivatives exhibited similar sequence specificities with only minor differences. However, PSO(O-S) differed from the other heteropsoralens. Photoadducts occurred with a higher frequency at AC and CA dinucleotides, and new sites were detected. A comparison with 8-methoxypsoralen photobinding is also reported. Finally, the mutagenic consequences of photoadducts induced in M13mp19 DNA by PSO(O-S) were determined in a forward system that detects all classes of mutagenic events. The high phototoxicity exhibited by PSO(O-S) could be attributed to crosslinks, and the comparison of the observed mutational specificity with the photoadduct distribution within the same gene showed that mutations were targeted at potential monoadduct sites where photolesions were detected in our footprinting experiments.

DNA Adducts↗

PubMed1996

Preferential repair incision of cross-links versus monoadducts in psoralen-damaged plasmid DNA by human cell-free extracts.

Upon UVA irradiation psoralens covalently bind to DNA as monoadduct and interstrand crosslink. Psoralen photoadducts are processed via an excision repair reaction that has been reproduced in vitro with transcriptionnally active cell-free extracts. A derived in vitro assay that allows direct quantification of the incised sites has been set up and used to compare the efficiency of the incision reaction on monoadducts and interstrand cross-links. The incision reaction was performed with HeLa cell-free extracts on angelicin or 8-methoxypsoralen (8-MOP)-modified plasmid DNA substrates carrying known amounts of mono- and biadducts, within various relative ratios. In the case of 8-MOP modified plasmids consisting in a mixture of mono- and biadducts on the same DNA molecule, the incision signal was mainly due to the presence of interstrand cross-links. The extent of incision was linear with the number of cross-links up to about 4 cross-links per plasmid and then reached a plateau. The sensitivity of incision defined as the increase of incision by 2-fold over the background level corresponded to about 1 cross-link per plasmid molecule, and about 7% of the total cross-links were repaired under our assay conditions. The incision activity on angelicin monoadducts yielded only 27% when compared to that on 8-MOP cross-links. Furthermore, 8-MOP cross-links lowered the incision extent of angelicin monoadducts when the two photoadducts were present on distinct plasmid DNA molecules. These data are in line with the more rapid excision of psoralen interstrand cross-links vs monoadducts observed in vivo.

Cell-Free System↗

PubMed1996

Mutagenic specificity of solar UV light in nucleotide excision repair-deficient rodent cells.

To investigate the role of nucleotide excision repair (NER) in the cellular processing of carcinogenic DNA photoproducts induced by defined, environmentally relevant portions of the solar wavelength spectrum, we have determined the mutagenic specificity of simulated sunlight (310-1100 nm), UVA (350-400 nm), and UVB (290-320 nm), as well as of the "nonsolar" model mutagen 254-nm UVC, at the adenine phosphoribosyltransferase (aprt) locus in NER-deficient (ERCC1) Chinese hamster ovary (CHO) cells. The frequency distributions of mutational classes induced by UVB and by simulated sunlight in repair-deficient CHO cells were virtually identical, each showing a marked increase in tandem CC-->TT transitions relative to NER-proficient cells. A striking increase in CC-->TT events was also previously documented for mutated p53 tumor-suppressor genes from nonmelanoma tumors of NER-deficient, skin cancer-prone xeroderma pigmentosum patients, compared to normal individuals. The data therefore indicate that the aprt gene in NER-deficient cultured rodent cells irradiated with artificial solar light generates the same distinctive "fingerprint" for sunlight mutagenesis as the p53 locus in NER-deficient humans exposed to natural sunlight in vivo. Moreover, in strong contrast to the situation for repair-component CHO cells, where a significant role for UVA was previously noted, the mutagenic specificity of simulated sunlight in NER-deficient CHO cells and of natural sunlight in humans afflicted with xeroderma pigmentosum can be entirely accounted for by the UVB portion of the solar wavelength spectrum.

Adenine Phosphoribosyltransferase↗

PubMed1996

Use of the alkaline comet assay to detect DNA repair deficiencies in human fibroblasts exposed to UVC, UVB, UVA and gamma-rays.

The alkaline single cell gel electrophoresis (comet) assay applied to human fibroblasts allowed us to analyze the response to components of the solar spectrum (UVB and UVA) in comparison with the well-established response to UVC and gamma-rays. DNA strand breaks related to nucleotide excision repair of DNA photoproducts were produced 1 h after exposure to UVB or UVC in the normal cell line but not in the repair deficient XPD and TTD-2 cell lines. In contrast, the immediate production of DNA strand breaks observed in all cell lines after exposure to UVA or gamma-rays was followed by restitution of high molecular weight DNA upon post-exposure incubation. These results imply that (1) fibroblasts as well as lymphocytes can be analysed by the comet assay and (2) the comet assay clearly distinguishes cellular nucleotide excision repair capacity without the use of inhibitors of DNA synthesis.

Cell Line↗

PubMed1994

The mutational specificity of simulated sunlight at the aprt locus in rodent cells.

To elucidate the nature of sunlight mutagenesis in mammalian cells, the mutational specificity of simulated solar light (SSL) has been established at the Chinese hamster ovary adenine phosphoribosyltransferase (aprt) locus. Among a collection of 36 independent SSL-induced mutations, the majority were single or tandem double C-->T transitions at dipyrimidine sites. This is consistent with previous investigations of 254 nm UVC on the aprt gene, as well as on various other genetic targets from diverse species, and supports a pre-eminent role for cyclobutane dimers and/or (6-4) photoproducts in solar mutagenesis. However, some substantial differences were also noted in the frequency and distribution of mutational classes generated by SSL versus UVC at the aprt locus. In particular, a reduction in the proportion of SSL-induced C-->T transitions was accompanied by significant increases in the incidence of T-->G transversions (25% versus 6%, P < 0.05) and of tandem double CC-->TT events at mutational hotspots (25% versus 9%, P < 0.05). Furthermore, a much greater fraction of SSL-induced mutations could be attributed to photoproducts on the non-transcribed strand of the aprt gene than was observed following treatment with 254 nm UV (94% versus 64%, P < 0.002). The general significance of these disparities between SSL and UVC mutagenesis at the aprt locus remains to be established, underscoring the need for further investigations on the effects of solar light in mammalian cells.

Adenine Phosphoribosyltransferase↗

PubMed1993

8-Methoxypsoralen induced mutations are highly targeted at crosslinkable sites of photoaddition on the non-transcribed strand of a mammalian chromosomal gene.

We have determined the mutational specificity of 8-methoxypsoralen photoaddition at the endogenous adenine phosphoribosyltransferase gene of Chinese hamster ovary cells hemizygous for this locus. In addition, the distribution of 8-methoxypsoralen photo-adducts was resolved in vitro at the DNA sequence level, and compared with the observed site specificity for mutation. Among 27 mutants characterized, all were single base changes at AT base pairs: 16 A:T-->T:A, six A:T-->C:G, four A:T-->G:C and one -T frameshift. All these vents were targeted to potential sites of photoaddition. The vast majority of these sites were also detectable in vitro, suggesting that 8-methoxypsoralen plus UVA-induced mutational hotspots may be damage hotspots. Furthermore 26/27 mutations occurred at crosslinkable 5'TpA sites, supporting the notion that 8-methoxypsoralen biadducts rather than monoadducts are major premutagenic lesions in mammalian cells. Since 90% of our mutation collection could have resulted from damage on the non-transcribed strand, it appears that photoadducted thymine residues on the transcribed strand of the adenine phosphoribosyltransferase gene may be preferentially repaired. We therefore suggest a model for mutagenesis, induced by psoralen biadducts, based on the preferential incision of biadducts followed by translesion synthesis past modified T bases persisting on the non-transcribed strand.

Adenine Phosphoribosyltransferase↗

PubMed1993

UV-induced G:C-->A:T transitions at the APRT locus of Chinese hamster ovary cells cluster at frequently damaged 5'-TCC-3' sequences.

We have determined the relative frequency in vitro of UV-induced cyclobutane pyrimidine dimers (py <> py) and (6-4) pyrimidine pyrimidone photoproducts (py(6-4)pyo) at individual sites in selected regions of the Chinese hamster ovary (CHO) adenine phosphoribosyltransferase (aprt) gene, and compared this to the observed specificity of UV-induced mutations (Drobetsky et al., 1987, 1989). Our results indicate that G:C-->A:T transition "hotspots" (multiple occurrences) at the chromosomal CHO aprt locus, the majority of which occur at 5'TCC-3', are clearly targeted at sites associated with a relatively high yield of py <> py and/or py(6-4)pyo. We conclude that photoproduct frequency plays a major role in UV-induced transition mutagenesis at 5'-TCC-3' sites at an endogenous locus in a rodent cell line, and that both py(6-4)pyo and py <> py have premutagenic potential.

Adenine Phosphoribosyltransferase↗

PubMed1993

Enzymatic recognition and biological effects of DNA damage induced by 3-carbethoxypsoralen plus UVA.

The specific recognition of DNA modifications by repair endonucleases was used to characterize damage induced by 3-carbethoxypsoralen (3-CPs) plus UvA in M13mp8 replicative form I (RF-I) DNA. Under the conditions used, 3-CPs plus UVA generates DNA base modifications which are recognized by the UvrABC complex and the Fpg protein of E. coli. The rate of formation of UvrABC sensitive sites is 3-4-fold higher than that of Fpg sensitive sites. In addition a small number of sites of base loss (sensitive to Nfo protein) were observed. M13mp8 RF-I DNA treated with 3-CPs plus UVA was tested for transfection efficiency in E. coli mutants defective in either Fpg protein and/or UvrABC complex. The survival of 3-CPs plus UVA damaged M13mp8 RF-I DNA was significantly reduced when transfected into uvrA mutants compared to that in the wild-type strain. On the other hand, the survival of 3-CPs plus UVA damaged RF-I DNA was not altered in fpg-1 mutants. These results show that nucleotide excision repair mediated by the UvrABC complex is the major repair pathway involved in the elimination of lethal lesions induced in DNA by 3-CPs plus UVA. Our data suggest that in vitro exposure of M13mp8 RF-I DNA to 3-CPs plus UVA produces predominantly thymine photoaddition and to a lesser extent guanine photooxidation partially due to singlet oxygen generated during photoreaction. The photoaddition products are primarly responsible for the observed lethal effect.

Binding Sites↗

PubMed1993

Long-term effects of cancer treatment and consequences of cure: cancer survivors enjoy quality of life similar to their neighbours.

To assess the long-term effects of cancer treatment and consequences of cure, 102 index cancer cases were compared with 95 neighbourhood controls of similar age and sex and with 78 cardiac controls. The quality of life experienced by these three groups was examined using multiple instruments with proven psychometric properties. All the major quality of life domains (physical, psychological and social) were covered. The findings revealed that the index cases were similar to their neighbours in areas of subjective well-being. However, the index cases exhibited more sexual dysfunction, were more conscientious, determined and emotionally disciplined, and applied the defence mechanisms of displacement and reaction formation more often than the neighbourhood controls. The cardiac controls were older, more anxious, more conventional/less imaginative and used suppression as a defence mechanism to a greater degree than the index cases. In conclusion, young adult cancer survivors enjoy a quality of life similar to their neighbours, whereas coronary bypass survivors adjust less well psychosocially.

Adolescent↗