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Environmental and Molecular Mutagenesis Apr 2024DNA damage occurs throughout life from a variety of sources, and it is imperative to repair damage in a timely manner to maintain genome stability. Thus, DNA repair... (Review)
Review
DNA damage occurs throughout life from a variety of sources, and it is imperative to repair damage in a timely manner to maintain genome stability. Thus, DNA repair mechanisms are a fundamental part of life. Nucleotide excision repair (NER) plays an important role in the removal of bulky DNA adducts, such as cyclobutane pyrimidine dimers from ultraviolet light or DNA crosslinking damage from platinum-based chemotherapeutics, such as cisplatin. A main component for the NER pathway is transcription factor IIH (TFIIH), a multifunctional, 10-subunit protein complex with crucial roles in both transcription and NER. In transcription, TFIIH is a component of the pre-initiation complex and is important for promoter opening and the phosphorylation of RNA Polymerase II (RNA Pol II). During repair, TFIIH is important for DNA unwinding, recruitment of downstream repair factors, and verification of the bulky lesion. Several different disease states can arise from mutations within subunits of the TFIIH complex. Most strikingly are xeroderma pigmentosum (XP), XP combined with Cockayne syndrome (CS), and trichothiodystrophy (TTD). Here, we summarize the recruitment and functions of TFIIH in the two NER subpathways, global genomic (GG-NER) and transcription-coupled NER (TC-NER). We will also discuss how TFIIH's roles in the two subpathways lead to different genetic disorders.
Topics: Humans; DNA; DNA Damage; DNA Repair; Excision Repair; Transcription Factor TFIIH; Transcription, Genetic; Xeroderma Pigmentosum
PubMed: 37545038
DOI: 10.1002/em.22568 -
Molecules (Basel, Switzerland) Jul 2023Diosmin is used to relieve chronic venous disease (CVD) symptoms. This study aimed to investigate the anti-inflammatory and antioxidant effects of...
Diosmin is used to relieve chronic venous disease (CVD) symptoms. This study aimed to investigate the anti-inflammatory and antioxidant effects of diosmetin-3--β-d-glucuronide, the major metabolite of diosmin, using human skin explants. The explants were exposed to substance P (inflammation model) or UVB irradiation (oxidative model) and to five diosmetin-3--β-d-glucuronide concentrations. Inflammation was evaluated through interleukin-8 (IL-8) secretion measurements and capillary dilation observation, and oxidation was evaluated by measuring the hydrogen peroxide levels and observing cyclobutane pyrimidine dimers (CPDs). In substance-P-exposed explants, diosmetin-3--β-d-glucuronide induced a significant decrease in IL-8 secretions, with a maximal effect at 2700 pg/mL (-49.6%), and it reduced the proportion of dilated capillaries and the mean luminal cross-sectional area ( < 0.0001 at all tested concentrations), indicating a vasoconstrictive effect. In UVB-irradiated fragments, diosmetin-3--β-d-glucuronide induced a significant decrease in hydrogen peroxide production and in the number of CPD-positive cells, reaching a maximal effect at the concentration of 2700 pg/mL (-48.6% and -52.0%, respectively). Diosmetin-3--β-d-glucuronide induced anti-inflammatory and antioxidant responses, with the maximal effect being reached at 2700 pg/mL and corresponding to the peak plasma concentration estimated after the oral intake of 600 mg of diosmin, the daily dose usually recommended for the treatment of CVD. These ex vivo findings suggest a protective role of diosmetin-3--β-d-glucuronide against inflammatory and oxidative stress affecting the vascular system in CVD pathophysiology.
Topics: Humans; Antioxidants; Glucuronides; Diosmin; Hydrogen Peroxide; Interleukin-8; Anti-Inflammatory Agents; Inflammation; Cardiovascular Diseases
PubMed: 37513462
DOI: 10.3390/molecules28145591 -
Metabolites Jun 2023The hormonal form of vitamin D, 1,25(OH)D, reduces UV-induced DNA damage. UV exposure initiates pre-vitamin D production in the skin, and continued UV exposure...
The hormonal form of vitamin D, 1,25(OH)D, reduces UV-induced DNA damage. UV exposure initiates pre-vitamin D production in the skin, and continued UV exposure photoisomerizes pre-vitamin D to produce "over-irradiation products" such as lumisterol (L). Cytochrome P450 side-chain cleavage enzyme (CYP11A1) in skin catalyzes the conversion of L to produce three main derivatives: 24-hydroxy-L [24(OH)L], 22-hydroxy-L [22(OH)L], and 20,22-dihydroxy-L [20,22(OH)L]. The current study investigated the photoprotective properties of the major over-irradiation metabolite, 24(OH)L, in human primary keratinocytes and human skin explants. The results indicated that treatment immediately after UV with either 24(OH)L or 1,25(OH)D reduced UV-induced cyclobutane pyrimidine dimers and oxidative DNA damage, with similar concentration response curves in keratinocytes, although in skin explants, 1,25(OH)D was more potent. The reductions in DNA damage by both compounds were, at least in part, the result of increased DNA repair through increased energy availability via increased glycolysis, as well as increased DNA damage recognition proteins in the nucleotide excision repair pathway. Reductions in UV-induced DNA photolesions by either compound occurred in the presence of lower reactive oxygen species. The results indicated that under in vitro and ex vivo conditions, 24(OH)L provided photoprotection against UV damage similar to that of 1,25(OH)D.
PubMed: 37512482
DOI: 10.3390/metabo13070775 -
JACS Au Jul 2023The direct and sequence-dependent investigation of photochemical processes in DNA on the way to cyclobutane pyrimidine dimers (CPDs) as DNA damage requires the probing...
The direct and sequence-dependent investigation of photochemical processes in DNA on the way to cyclobutane pyrimidine dimers (CPDs) as DNA damage requires the probing by photochemically different photosensitizers. The C-nucleosides of xanthone, thioxanthone, 3-methoxyxanthone, and triphenylene as photosensitizers were synthesized by Heck couplings and incorporated into ternary photoactive DNA architectures. This structural approach allows the site-selective excitation of the DNA by UV light. Together with a single defined site for T-T dimerization, not only the direct CPD formation but also the distance-dependent CPD formation in DNA as well as the possibility for energy transport processes could be investigated. Direct CPD formation was observed with xanthone, 3-methoxyxanthone, and triphenylene as sensitizers but not with thioxanthone. Only xanthone was able to induce CPDs remotely by a triplet energy transfer over up to six intervening A-T base pairs. Taken together, more precise information on the sequence dependence of the DNA triplet photochemistry was obtained.
PubMed: 37502149
DOI: 10.1021/jacsau.3c00167 -
The Journal of Physical Chemistry. B Aug 2023Methylation at the C5 position of cytosine, a naturally occurring epigenetic modification on DNA, shows a high correlation with mutational hotspots in disease such as...
Methylation at the C5 position of cytosine, a naturally occurring epigenetic modification on DNA, shows a high correlation with mutational hotspots in disease such as skin cancer. Due to its essential biological relevance, numerous studies were devoted to confirming that the methylated sites favor the formation of the cyclobutane pyrimidine dimer (CPD), a well-known UV-induced lesion. However, photophysical and photochemical properties of dinucleotides and polynucleotides containing 5-methylcytosine (C) remain elusive. Herein, a charge transfer (CT) triplet state, generated via intersystem crossing (ISC) from a CT singlet state that enhanced after methylation on cytosine, is directly observed by using femtosecond transient absorption (TA) and time-resolved mid-infrared (TRIR) spectroscopy together with quantum chemical calculations for the first time in the TC dimer. Such an ISC process is quenched due to limitations of the ground-state geometries in C-containing single-strand oligomer d(TC). This mechanistic information is important for understanding the early stage of triplet state-induced CPD formation in C containing DNA.
Topics: 5-Methylcytosine; Pyrimidine Dimers; DNA Damage; Cytosine; DNA
PubMed: 37490365
DOI: 10.1021/acs.jpcb.3c02454 -
Journal of Photochemistry and... Aug 2023The application of a far-ultraviolet C (UVC) light emitting diode (LED) of 233 nm showed significant bactericidal efficacy at an applied dose between 20 and 80 mJ cm...
The application of a far-ultraviolet C (UVC) light emitting diode (LED) of 233 nm showed significant bactericidal efficacy at an applied dose between 20 and 80 mJ cm as reported recently. In addition, only minor epidermal DNA lesions were observed in ex vivo human skin and in vitro epidermal models <10% of the minimal erythema dose of UVB radiation. To broaden the potential range of applications of such systems, e.g. to include postoperative application on wounds for the purpose of decontamination, we assessed how a disruption of normal anatomic skin structure and function influences the skin damage induced by light from 233 nm far-UVC LEDs. Thus, we induced superficial skin wounds by mechanical detachment of the stratum corneum in ex vivo human skin. Barrier-disruption of the skin could be successfully determined by measuring an increase in the transepidermal water loss (TEWL) and the stratum corneum loss could be determined morphologically by 2-photon microscopy (2-PM). After far-UVC irradiation of the skin, we screened the tissue for the development of cyclobutane pyrimidine dimers (CPDs) and 6-4 photoproducts (6-4PPs). The abundance of DNA lesions was elevated in wound skin in comparison to intact skin after irradiation with far-UVC. However, no increase in DNA lesions was detected when artificial wound exudate consisting of cell culture medium and serum was applied to the disrupted skin surface prior to irradiation. This effect agrees with the results of ray tracing simulations of the absorption of far-UVC light incident on a superficial skin wound. Interestingly, no significant deviations in radical formation between intact skin and superficially wounded skin were detected after far-UVC irradiation as analyzed by electron paramagnetic resonance (EPR) spectroscopy. In conclusion, 233 nm LED light at a dose of 60 mJ/cm could be applied safely on superficial wounds for the purpose of skin antisepsis as long as the wounds are covered with wound fluid.
Topics: Humans; Skin; Pyrimidine Dimers; Epidermis; DNA; Ultraviolet Rays; DNA Damage
PubMed: 37481791
DOI: 10.1016/j.jphotobiol.2023.112757 -
The Journal of Physical Chemistry... Jul 2023The repair of the cyclobutane pyrimidine dimer (CPD) lesion in DNA by photolyase is determined by its initial recognition, and the catalytic efficiency depends on a...
The repair of the cyclobutane pyrimidine dimer (CPD) lesion in DNA by photolyase is determined by its initial recognition, and the catalytic efficiency depends on a series of intermolecular electron-transfer (ET) processes. Here, we investigated the repair of a CPD structural isomer, replacing the deoxyribose with a pyranose sugar on the 5' site, and found a loss in binding efficiency and repair quantum yield. Using femtosecond spectroscopy, we characterized all elementary repair steps and observed a systemic slowdown of the four intermolecular ET reactions and the second bond splitting. Our observations and molecular dynamics simulations suggest that the sugar replacement disrupts the lesion binding configuration, weakening the electronic coupling between the cofactor and lesion and altering the stability of lesion intermediates. These findings highlight how the CPD photolyases have utilized the structural features of the CPD lesion and optimized its interactions with the cofactor and key active-site residues to maximize repair yields.
Topics: Deoxyribodipyrimidine Photo-Lyase; DNA Repair; Pyrimidine Dimers; DNA Damage; Sugars
PubMed: 37463310
DOI: 10.1021/acs.jpclett.3c01128 -
Biochemistry Aug 2023G-quadruplexes are thought to play an important role in gene regulation and telomere maintenance, but developing probes for their presence and location is challenging...
Post- and Pre-Radiolabeling Assays for Thymidine Cyclobutane Dimers as Intrinsic Photoprobes of Various Types of G-Quadruplexes, Reverse Hoogsteen Hairpins, and Other Non-B DNA Structures.
G-quadruplexes are thought to play an important role in gene regulation and telomere maintenance, but developing probes for their presence and location is challenging due to their transitory and highly dynamic nature. The majority of probes for G-quadruplexes have relied on antibody or small-molecule binding agents, many of which can also alter the dynamics and relative populations of G-quadruplexes. Recently, it was discovered that ultraviolet B (UVB) irradiation of human telomeric DNA and various G-quadruplex forming sequences found in human promoters, as well as reverse Hoogsteen hairpins, produces a unique class of non-adjacent cyclobutane pyrimidine dimers (CPDs). Therefore, one can envision using a pulse of UVB light to irreversibly trap these non-B DNA structures via CPD formation without perturbing their dynamics, after which the CPDs can be identified and mapped. As a first step toward this goal, we report radioactive post- and pre-labeling assays for the detection of non-adjacent CPDs and illustrate their use in detecting , T=(T) CPD formation in a human telomeric DNA sequence. Both assays make use of snake venom phosphodiesterase (SVP) to degrade the , T=(T) CPD-containing DNA to the tetranucleotide pT=(pT) corresponding to CPD formation between the underlined T's of two separate dinucleotides while degrading the adjacent TT CPDs to the trinucleotide pGT=T. In the post-labeling assay, calf intestinal phosphodiesterase is used to dephosphorylate the tetranucleotides, which are then rephosphorylated with kinase and [P]-ATP to produce radiolabeled mono- and diphosphorylated tetranucleotides. The tetranucleotides are confirmed to be non-adjacent CPDs by 254 nm photoreversion to the dinucleotide p*TT. In the pre-labeling assay, radiolabeled phosphates are introduced into non-adjacent CPD-forming sites by ligation prior to irradiation, thereby eliminating the dephosphorylation and rephosphorylation steps. The assays are also demonstrated to detect the stereoisomeric , T=(T) CPD.
Topics: Humans; G-Quadruplexes; DNA; Pyrimidine Dimers; Ultraviolet Rays; DNA Damage
PubMed: 37459251
DOI: 10.1021/acs.biochem.3c00155 -
The Journal of Organic Chemistry Jul 2023The quest for simple systems achieving the photoreductive splitting of four-membered ring compounds is a matter of interest not only in organic chemistry but also in...
The quest for simple systems achieving the photoreductive splitting of four-membered ring compounds is a matter of interest not only in organic chemistry but also in biochemistry to mimic the activity of DNA photorepair enzymes. In this context, 8-oxoguanine, the main oxidatively generated lesion of guanine, has been shown to act as an intrinsic photoreductant by transferring an electron to bipyrimidine lesions and provoking their cycloreversion. But, in spite of appropriate photoredox properties, the capacity of guanine to repair cyclobutane pyrimidine dimer is not clearly established. Here, dyads containing the cyclobutane thymine dimer and guanine or 8-oxoguanine are synthesized, and their photoreactivities are compared. In both cases, the splitting of the ring takes place, leading to the formation of thymine, with a quantum yield 3.5 times lower than that for the guanine derivative. This result is in agreement with the more favored thermodynamics determined for the oxidized lesion. In addition, quantum chemistry calculations and molecular dynamics simulations are carried out to rationalize the crucial aspects of the overall cyclobutane thymine dimer photoreductive repair triggered by the nucleobase and its main lesion.
Topics: Pyrimidine Dimers; Cyclobutanes; Thymine; DNA; Guanine
PubMed: 37437138
DOI: 10.1021/acs.joc.3c00930 -
Cells Jun 2023Ultraviolet (UV) radiation is a strong environmental carcinogen responsible for the pathogenesis of most skin cancers, including malignant melanoma (MM) and non-melanoma...
Ultraviolet (UV) radiation is a strong environmental carcinogen responsible for the pathogenesis of most skin cancers, including malignant melanoma (MM) and non-melanoma (keratinocyte) skin cancers. The carcinogenic role of UV was firmly established based on epidemiological evidence and molecular findings of the characteristic mutation signatures which occur during the excision repair of cyclobutane pyrimidine dimers and 6,4-photoproducts. The role of UV in the pathogenesis of mycosis fungoides (MF), the most common type of primary cutaneous T-cell lymphoma, remains controversial. Here, we performed whole-exome sequencing of 61 samples of MF cells microdissected from cutaneous lesions, and compared their mutational signatures to 340 MMs. The vast majority of MM mutations had a typical UV mutational signature (SBS 7, SBS 38, or DSB 1), underscoring the key role of ultraviolet as a mutagen. In contrast, the SBS 7 signature in MF comprised < 5% of all mutations. SBS 7 was higher in the intraepidermal MF cells (when compared to the dermal cells) and in the cells from tumors as compared to that in early-stage plaques. In conclusion, our data do not support the pathogenic role of UV in the pathogenesis of MF and suggest that the UV mutations are the result of the cumulative environmental ultraviolet exposure of cutaneous lesions rather than an early mutagenic event.
Topics: Humans; Ultraviolet Rays; Skin Neoplasms; Mycosis Fungoides; Melanoma; Mutation; Melanoma, Cutaneous Malignant
PubMed: 37371087
DOI: 10.3390/cells12121616