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Very high sensitivity of African rice to artificial ultraviolet-B radiation caused by genotype and quantity of cyclobutane pyrimidine dimer photolyase.

ABSTRACT: Ultraviolet-B (UVB) radiation damages plants and decreases their growth and productivity. We previously demonstrated that UVB sensitivity varies widely among Asian rice (Oryza sativa L.) cultivars and that the activity of cyclobutane pyrimidine dimer (CPD) photolyase, which repairs UVB-induced CPDs, determines UVB sensitivity. Unlike Asian rice, African rice (Oryza glaberrima Steud. and Oryza barthii A. Chev.) has mechanisms to adapt to African climates and to protect itself against biotic and abiotic stresses. However, information about the UVB sensitivity of African rice species is largely absent. We showed that most of the African rice cultivars examined in this study were UVB-hypersensitive or even UVB-super-hypersensitive in comparison with the UVB sensitivity of Asian O. sativa cultivars. The difference in UVB resistance correlated with the total CPD photolyase activity, which was determined by its activity and its cellular content. The UVB-super-hypersensitive cultivars had low enzyme activity caused by newly identified polymorphisms and low cellular CPD photolyase contents. The new polymorphisms were only found in cultivars from West Africa, particularly in those from countries believed to be centres of O. glaberrima domestication. This study provides new tools for improving both Asian and African rice productivity.

SUBMITTER: Mmbando GS

PROVIDER: S-EPMC7035317 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Eukaryotic class II cyclobutane pyrimidine dimer photolyase structure reveals basis for improved ultraviolet tolerance in plants.

Project description:Ozone depletion increases terrestrial solar ultraviolet B (UV-B; 280-315 nm) radiation, intensifying the risks plants face from DNA damage, especially covalent cyclobutane pyrimidine dimers (CPD). Without efficient repair, UV-B destroys genetic integrity, but plant breeding creates rice cultivars with more robust photolyase (PHR) DNA repair activity as an environmental adaptation. So improved strains of Oryza sativa (rice), the staple food for Asia, have expanded rice cultivation worldwide. Efficient light-driven PHR enzymes restore normal pyrimidines to UV-damaged DNA by using blue light via flavin adenine dinucleotide to break pyrimidine dimers. Eukaryotes duplicated the photolyase gene, producing PHRs that gained functions and adopted activities that are distinct from those of prokaryotic PHRs yet are incompletely understood. Many multicellular organisms have two types of PHR: (6-4) PHR, which structurally resembles bacterial CPD PHRs but recognizes different substrates, and Class II CPD PHR, which is remarkably dissimilar in sequence from bacterial PHRs despite their common substrate. To understand the enigmatic DNA repair mechanisms of PHRs in eukaryotic cells, we determined the first crystal structure of a eukaryotic Class II CPD PHR from the rice cultivar Sasanishiki. Our 1.7 Å resolution PHR structure reveals structure-activity relationships in Class II PHRs and tuning for enhanced UV tolerance in plants. Structural comparisons with prokaryotic Class I CPD PHRs identified differences in the binding site for UV-damaged DNA substrate. Convergent evolution of both flavin hydrogen bonding and a Trp electron transfer pathway establish these as critical functional features for PHRs. These results provide a paradigm for light-dependent DNA repair in higher organisms.

| S-EPMC3320952 | biostudies-literature

qUVR-10, a major quantitative trait locus for ultraviolet-B resistance in rice, encodes cyclobutane pyrimidine dimer photolyase.

Project description:Rice qUVR-10, a quantitative trait locus (QTL) for ultraviolet-B (UVB) resistance on chromosome 10, was cloned by map-based strategy. It was detected in backcross inbred lines (BILs) derived from a cross between the japonica variety Nipponbare (UV resistant) and the indica variety Kasalath (UV sensitive). Plants homozygous for the Nipponbare allele at the qUVR-10 locus were more resistant to UVB compared with the Kasalath allele. High-resolution mapping using 1850 F(2) plants enabled us to delimit qUVR-10 to a <27-kb genomic region. We identified a gene encoding the cyclobutane pyrimidine dimer (CPD) photolyase in this region. Activity of CPD photorepair in Nipponbare was higher than that of Kasalath and nearly isogenic with qUVR-10 [NIL(qUVR-10)], suggesting that the CPD photolyase of Kasalath was defective. We introduced a genomic fragment containing the CPD photolyase gene of Nipponbare to NIL(qUVR-10). Transgenic plants showed the same level of resistance as Nipponbare did, indicating that the qUVR-10 encoded the CPD photolyase. Comparison of the qUVR-10 sequence in the Nipponbare and Kasalath alleles revealed one probable candidate for the functional nucleotide polymorphism. It was indicated that single-base substitution in the CPD photolyase gene caused the alteration of activity of CPD photorepair and UVB resistance. Furthermore, we were able to develop a UV-hyperresistant plant by overexpression of the photolyase gene.

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Dynamics and mechanism of cyclobutane pyrimidine dimer repair by DNA photolyase.

Project description:Photolyase uses blue light to restore the major ultraviolet (UV)-induced DNA damage, the cyclobutane pyrimidine dimer (CPD), to two normal bases by splitting the cyclobutane ring. Our earlier studies showed that the overall repair is completed in 700 ps through a cyclic electron-transfer radical mechanism. However, the two fundamental processes, electron-tunneling pathways and cyclobutane ring splitting, were not resolved. Here, we use ultrafast UV absorption spectroscopy to show that the CPD splits in two sequential steps within 90 ps and the electron tunnels between the cofactor and substrate through a remarkable route with an intervening adenine. Site-directed mutagenesis reveals that the active-site residues are critical to achieving high repair efficiency, a unique electrostatic environment to optimize the redox potentials and local flexibility, and thus balance all catalytic reactions to maximize enzyme activity. These key findings reveal the complete spatio-temporal molecular picture of CPD repair by photolyase and elucidate the underlying molecular mechanism of the enzyme's high repair efficiency.

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Discrimination of class I cyclobutane pyrimidine dimer photolyase from blue light photoreceptors by single methionine residue.

Project description:DNA photolyase recognizes ultraviolet-damaged DNA and breaks improperly formed covalent bonds within the cyclobutane pyrimidine dimer by a light-activated electron transfer reaction between the flavin adenine dinucleotide, the electron donor, and cyclobutane pyrimidine dimer, the electron acceptor. Theoretical analysis of the electron-tunneling pathways of the DNA photolyase derived from Anacystis nidulans can reveal the active role of the protein environment in the electron transfer reaction. Here, we report the unexpectedly important role of the single methionine residue, Met-353, where busy trafficking of electron-tunneling currents is observed. The amino acid conservation pattern of Met-353 in the homologous sequences perfectly correlates with experimentally verified annotation as photolyases. The bioinformatics sequence analysis also suggests that the residue plays a pivotal role in biological function. Consistent findings from different disciplines of computational biology strongly suggest the pivotal role of Met-353 in the biological function of DNA photolyase.

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The class III cyclobutane pyrimidine dimer photolyase structure reveals a new antenna chromophore binding site and alternative photoreduction pathways.

Project description:Photolyases are proteins with an FAD chromophore that repair UV-induced pyrimidine dimers on the DNA in a light-dependent manner. The cyclobutane pyrimidine dimer class III photolyases are structurally unknown but closely related to plant cryptochromes, which serve as blue-light photoreceptors. Here we present the crystal structure of a class III photolyase termed photolyase-related protein A (PhrA) of Agrobacterium tumefaciens at 1.67-Å resolution. PhrA contains 5,10-methenyltetrahydrofolate (MTHF) as an antenna chromophore with a unique binding site and mode. Two Trp residues play pivotal roles for stabilizing MTHF by a double π-stacking sandwich. Plant cryptochrome I forms a pocket at the same site that could accommodate MTHF or a similar molecule. The PhrA structure and mutant studies showed that electrons flow during FAD photoreduction proceeds via two Trp triads. The structural studies on PhrA give a clearer picture on the evolutionary transition from photolyase to photoreceptor.

| S-EPMC4416854 | biostudies-literature

Identification of Cyclobutane Pyrimidine Dimer-Responsive Genes Using UVB-Irradiated Human Keratinocytes Transfected with In Vitro-Synthesized Photolyase mRNA.

Project description:Major biological effects of UVB are attributed to cyclobutane pyrimidine dimers (CPDs), the most common photolesions formed on DNA. To investigate the contribution of CPDs to UVB-induced changes of gene expression, a model system was established by transfecting keratinocytes with pseudouridine-modified mRNA (Ψ-mRNA) encoding CPD-photolyase. Microarray analyses of this model system demonstrated that more than 50% of the gene expression altered by UVB was mediated by CPD photolesions. Functional classification of the gene targets revealed strong effects of CPDs on the regulation of the cell cycle and transcriptional machineries. To confirm the microarray data, cell cycle-regulatory genes, CCNE1 and CDKN2B that were induced exclusively by CPDs were selected for further investigation. Following UVB irradiation, expression of these genes increased significantly at both mRNA and protein levels, but not in cells transfected with CPD-photolyase Ψ-mRNA and exposed to photoreactivating light. Treatment of cells with inhibitors of c-Jun N-terminal kinase (JNK) blocked the UVB-dependent upregulation of both genes suggesting a role for JNK in relaying the signal of UVB-induced CPDs into transcriptional responses. Thus, photolyase mRNA-based experimental platform demonstrates CPD-dependent and -independent events of UVB-induced cellular responses, and, as such, has the potential to identify novel molecular targets for treatment of UVB-mediated skin diseases.

| S-EPMC4488231 | biostudies-literature

ASH1L guards cis-regulatory elements against cyclobutane pyrimidine dimer induction

Project description:The histone methyltransferase ASH1L, first discovered for its role in transcription, has been shown to accelerate the removal of ultraviolet (UV) light-induced cyclobutane pyrimidine dimers (CPDs) by nucleotide excision repair. Previous reports demonstrated that CPD excision is most efficient at transcriptional regulatory elements, including enhancers, relative to other genomic sites. Therefore, we analyzed DNA damage maps in ASH1L-proficient and ASH1L-deficient cells to understand how ASH1L controls enhancer stability. This comparison showed that ASH1L protects enhancer sequences against the induction of CPDs besides stimulating repair activity. ASH1L reduces CPD formation at C-containing but not at TT dinucleotides, and no protection occurs against pyrimidine-(6,4)-pyrimidone photoproducts or cisplatin crosslinks. The diminished CPD induction extends to gene promoters but excludes retrotransposons. This guardian role against CPDs in regulatory elements is associated with the presence of H3K4me3 and H3K27ac histone marks, which are known to interact with the PHD and BRD motifs of ASH1L, respectively. Molecular dynamics simulations identified a DNA-binding AT hook of ASH1L that alters the distance and dihedral angle between neighboring C nucleotides to disfavor dimerization. The loss of this protection results in a higher frequency of C–>T transitions at enhancers of skin cancers carrying ASH1L mutations compared to ASH1L-intact counterparts.

2024-06-02 | GSE260917 | GEO

Cyclobutane Pyrimidine Dimer Density as a Predictive Biomarker of the Biological Effects of Ultraviolet Radiation in Normal Human Fibroblast.

Project description:This study compared biological responses of normal human fibroblasts (NHF1) to three sources of ultraviolet radiation (UVR), emitting UVC wavelengths, UVB wavelengths, or a combination of UVA and UVB (solar simulator; emission spectrum, 94.3% UVA and 5.7% UVB). The endpoints measured were cytotoxicity, intra-S checkpoint activation, inhibition of DNA replication and mutagenicity. Results show that the magnitude of each response to the indicated radiation sources was best predicted by the density of DNA cyclobutane pyrimidine dimers (CPD). The density of 6-4 pyrimidine-pyrimidone photoproducts was highest in DNA from UVC-irradiated cells (14% of CPD) as compared to those exposed to UVB (11%) or UVA-UVB (7%). The solar simulator source, under the experimental conditions described here, did not induce the formation of 8-oxo-7,8-dihydroguanine in NHF1 above background levels. Taken together, these results suggest that CPD play a dominant role in DNA damage responses and highlight the importance of using endogenous biomarkers to compare and report biological effects induced by different sources of UVR.

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Crystal structure of thermostable DNA photolyase: pyrimidine-dimer recognition mechanism.

Project description:DNA photolyase is a pyrimidine-dimer repair enzyme that uses visible light. Photolyase generally contains two chromophore cofactors. One is a catalytic cofactor directly contributing to the repair of a pyrimidine-dimer. The other is a light-harvesting cofactor, which absorbs visible light and transfers energy to the catalytic cofactor. Photolyases are classified according to their second cofactor into either a folate- or deazaflavin-type. The native structures of both types of photolyases have already been determined, but the mechanism of substrate recognition remains largely unclear because of the lack of structural information regarding the photolyase-substrate complex. Photolyase from Thermus thermophilus, the first thermostable class I photolyase found, is favorable for function analysis, but even the type of the second cofactor has not been identified. Here, we report the crystal structures of T. thermophilus photolyase in both forms of the native enzyme and the complex along with a part of its substrate, thymine. A structural comparison with other photolyases suggests that T. thermophilus photolyase has structural features allowing for thermostability and that its light-harvesting cofactor binding site bears a close resemblance to a deazaflavin-type photolyase. One thymine base is found at the hole, a putative substrate-binding site near the catalytic cofactor in the complex form. This structural data for the photolyase-thymine complex allow us to propose a detailed model for the pyrimidine-dimer recognition mechanism.

| S-EPMC61080 | biostudies-literature

Kinetics of cyclobutane thymine dimer splitting by DNA photolyase directly monitored in the UV.

Project description:CPD photolyase uses light to repair cyclobutane pyrimidine dimers (CPDs) formed between adjacent pyrimidines in UV-irradiated DNA. The enzyme harbors an FAD cofactor in fully reduced state (FADH(-)). The CPD repair mechanism involves electron transfer from photoexcited FADH(-) to the CPD, splitting of its intradimer bonds, and electron return to restore catalytically active FADH(-). The two electron transfer processes occur on time scales of 10(-10) and 10(-9) s, respectively. Until now, CPD splitting itself has only been poorly characterized by experiments. Using a previously unreported transient absorption setup, we succeeded in monitoring cyclobutane thymine dimer repair in the main UV absorption band of intact thymine at 266 nm. Flavin transitions that overlay DNA-based absorption changes at 266 nm were monitored independently in the visible and subtracted to obtain the true repair kinetics. Restoration of intact thymine showed a short lag and a biexponential rise with time constants of 0.2 and 1.5 ns. We assign these two time constants to splitting of the intradimer bonds (creating one intact thymine and one thymine anion radical T(?-)) and electron return from T(?-) to the FAD cofactor with recovery of the second thymine, respectively. Previous model studies and computer simulations yielded various CPD splitting times between < 1 ps and < 100 ns. Our experimental results should serve as a benchmark for future efforts to model enzymatic photorepair. The technique and methods developed here may be applied to monitor other photoreactions involving DNA.

| S-EPMC3111307 | biostudies-literature

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