| 1. |
- Bergström, Petra, et al.
(författare)
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Association of NFE2L2 and KEAP1 haplotypes with amyotrophic lateral sclerosis.
- 2014
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Ingår i: Amyotrophic lateral sclerosis & frontotemporal degeneration. - : Informa UK Limited. - 2167-9223 .- 2167-8421. ; 15:1-2, s. 130-137
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Tidskriftsartikel (refereegranskat)abstract
- Amyotrophic lateral sclerosis (ALS) is a degenerative motor neuron syndrome influenced by oxidative stress. The transcription factor Nrf2 and its repressor Keap1 constitute an important defence system in cellular protection against oxidative stress. Here we hypothesize that common genetic variations in the genes NFE2L2 and KEAP1, encoding Nrf2 and Keap1, may influence the risk and phenotype of ALS. Five hundred and twenty-two Swedish patients with sporadic ALS (SALS) and 564 Swedish control subjects were studied. Eight tag SNPs in NFE2L2 and three tag SNPs in KEAP1 were genotyped by allelic discrimination and three functional NFE2L2 promoter SNPs were genotyped by sequencing. One NFE2L2 haplotype (GGGAC) was associated with decreased risk of SALS (OR = 0.62 per allele, p = 0.003) and one haplotype in KEAP1 (CGG) was associated with later SALS onset (+3.4 years per allele, p = 0.015). When stratified by subgroup, one haplotype in NFE2L2, GAGCAGA including three functional promoter SNPs associated with high Nrf2 protein expression, was associated with 4.0 years later disease onset per allele in subgroup ALS (p = 0.008). In conclusion, these results suggest that variations in NFE2L2 and KEAP1, encoding two central proteins in cellular oxidative stress defence, may influence SALS pathogenesis.
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| 2. |
- Grankvist, Kjell, et al.
(författare)
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Laboratoriernas verksamhet
- 2018. - 10
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Ingår i: Laurells Klinisk kemi i praktisk medicin. - Lund : Studentlitteratur AB. - 9789144119748 ; , s. 13-30
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Bokkapitel (refereegranskat)
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| 3. |
- Hammarsten, Ola, et al.
(författare)
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Tolkning av analysresultat
- 2018. - 10
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Ingår i: Laurells Klinisk kemi i praktisk medicin. - Lund : Studentlitteratur AB. - 9789144119748 ; , s. 31-53
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Bokkapitel (refereegranskat)
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| 4. |
- Klingberg, Eva, et al.
(författare)
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The vitamin D status in ankylosing spondylitis in relation to intestinal inflammation, disease activity, and bone health: a cross-sectional study
- 2016
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Ingår i: Osteoporosis International. - : Springer Science and Business Media LLC. - 0937-941X .- 1433-2965. ; 27:6, s. 2027-2033
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Tidskriftsartikel (refereegranskat)abstract
- We assessed the vitamin D status in ankylosing spondylitis (AS) patients and healthy controls in the late winter when no vitamin D is produced by the sunlight. The vitamin D status was often poor, but not lower in AS and not associated with disease activity or signs of gut inflammation. The aims of the study were to investigate the vitamin D levels attained mainly by dietary intake in ankylosing spondylitis (AS) in comparison with healthy controls and in relation to gut inflammation, measured indirectly by fecal calprotectin, disease activity, osteoproliferation, bone mineral density (BMD), and vertebral fractures. Serum 25-hydroxy vitamin D (25(OH)D) was measured in 203 AS patients and 120 healthy controls at the end of "the vitamin D winter," when the out-door UVB irradiation is too low to allow synthesis of vitamin D-3 in the skin at the latitude of Gothenburg, Sweden. Fecal calprotectin was measured in stool samples. Disease activity was assessed with CRP, ESR, ASDAS(CRP,) BASDAI, BAS-G, BASFI, and BASMI. Lateral spine radiographs were scored for osteoproliferation and vertebral fractures using the mSASSS and Genant scores. BMD was measured in the lumbar spine and femoral neck. Vitamin D insufficiency (a serum 25(OH)D < 50 nmol/L) was found in approximately 50 % of the AS patients, but serum 25(OH)D was not different from healthy controls and not significantly correlated with fecal calprotectin, gastrointestinal symptoms, disease activity parameters, mSASSS, BMD, or vertebral fractures. The vitamin D status was often poor in the late winter in AS but not different from the healthy controls. No evidence for a connection between subclinical gut inflammation, malabsorption, and hypovitaminosis D was found. Serum 25(OH)D was not associated with disease activity, osteoproliferation, BMD, or vertebral fractures. We suggest that the lower vitamin D levels in AS, previously found by others, may be caused by reduced out-door UVB exposure.
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| 5. |
- Sabouri, Nasim, 1978-
(författare)
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Structure of eukaryotic DNA polymerase epsilon and lesion bypass capability
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- To transfer the information in the genome from mother cell to daughter cell, the DNA replication must be carried out only once and with very high fidelity prior to every cell division. In yeast there are several different DNA polymerases involved in DNA replication and/or DNA repair. The two replicative DNA polymerases, DNA polymerase delta (Pol delta) and DNA polymerase epsilon (Pol epsilon), which both include a proofreading 3´→5´exonuclease activity, can replicate and proofread the genome with a very high degree of accuracy. The aim of this thesis was to gain a better understanding of how the enigmatic DNA polymerase epsilon participates in DNA transactions. To investigate whether Pol epsilon or Pol delta is responsible for the synthesis of DNA on the lagging strand, the processing and assembly of Okazaki fragments was studied. Pol delta was found to have a unique property called “idling” which, together with the flap-endonuclease (FEN1), maintained a ligatable nick for DNA ligase I. In contrast, Pol epsilon was found to lack the ability to “idle” and interact functionally with FEN-1, indicating that Pol epsilon is not involved in processing Okazaki fragments. Together with previous genetic studies, it was concluded that Pol delta is the preferred lagging strand polymerase, leaving Pol epsilon to carry out some other function. The structure of Pol epsilon was determined by cryo-electron microscopy, to a resolution of ~20 Å. Pol epsilon is composed of a globular “head” domain consisting of the large catalytic subunit Pol2p, and a “tail” domain, consisting of the small subunits Dpb2p, Dpb3p, and Dpb4p. The two separable domains were found to be connected by a flexible hinge. Interestingly, the high intrinsic processivity of Pol epsilon depends on the interaction between the tail domain and double-stranded DNA. As a replicative DNA polymerase, Pol epsilon encounters different lesions in DNA. It was shown that Pol epsilon can perform translesion synthesis (TLS) through a model abasic site in the absence of external processivity clamps under single-hit conditions. The lesion bypass was dependent of the sequence on the template and also on a proper interaction of the “tail”domain with the primer-template. Yeast cells treated with a DNA damaging agent and devoid of all TLS polymerases showed improved survival rates in the presence of elevated levels of dNTPs. These genetic results suggested that replicative polymerases may be engaged in the bypass of some DNA lesions. In vitro, Pol epsilon was found to bypass 8-OxoG at elevated dNTP levels. Together, the in vitro and in vivo results suggest that the replicative polymerases may be engaged in bypass of less bulky DNA lesions at elevated dNTP levels. In conclusion, the low-resolution structure presented represents the first structural characterization of a eukaryotic multi-subunit DNA polymerase. The replicative DNA polymerase Pol epsilon can perform translesion synthesis due to an interaction between the tail domain and double-stranded DNA. Pol epsilon may also bypass less bulky DNA lesions when there are elevated dNTP concentrations in vivo.
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| 6. |
- Tran, Phong, 1987-
(författare)
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Pathology of dNTP dysregulation
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Deoxyribonucleoside triphosphates (dNTPs) are precursors for DNA replication and repair. Mammalian cells have two distinct biosynthesis pathways to supply dNTPs: de novo and salvage pathways. These pathways are intimately coordinated to maintain optimal dNTP concentrations throughout different phases of the cell cycle, and perturbations in the production of dNTPs could lead to increased, decreased, or imbalanced dNTP pools. In yeasts, changes in both the level and balance of dNTPs increase mutation rates and genome instability. In mammals, elevated mutation rates and genome instability predispose to numerous diseases, including cancer. However, the correlation of dNTP changes with pathology has not been well established in mammals. In this thesis, I present how we addressed this issue using three separate mouse models – one with an increased dNTP pool, one with a decreased dNTP pool, and one with an imbalanced dNTP pool. To modulate dNTP levels in the mice, we deleted or mutated either sterile alpha motif and histidine-aspartic domain containing protein 1 (SAMHD1) or ribonucleotide reductase (RNR) proteins, which are involved in the salvage and de novo pathways, respectively. In the first model, mouse embryos without the SAMHD1 gene showed a slight increase in dNTP levels. A similar increase in dNTPs conferred moderately elevated mutation rates in cultured cancer cells. In the second model, we created a mouse strain carrying a modified allosteric specificity site in a subunit of RNR. Embryos with a heterozygous mutation had a mildly imbalanced dNTP pool. Heterozygous mutant mice showed a shorter lifespan and increased incidence and earlier onset of cancer. In the third model, the de novo dNTP production was inactivated in cardiac and skeletal muscles through the deletion of a gene encoding RNR. The hearts of knockout pups showed significant depletion of dNTPs, leading to aberrant DNA replication. In addition, knockout pups developed anatomic and histologic cardiac abnormalities and impaired cardiac conduction systems. As a result, they died between two and four weeks after birth. Taken together, our studies provide the first empirical evidence that both the de novo and salvage pathways are essential to keeping the dNTP concentration at an optimal range to prevent mutagenesis, carcinogenesis, and mortality.
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| 7. |
- Tsaponina, Olga, 1978-
(författare)
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Regulation of ribonucleotide reductase and the role of dNTP pools in genomic stability in yeast Saccharomyces cerevisiae
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Every living organism is programmed to reproduce and to pass genetic information to descendants. The information has to be carefully copied and accurately transferred to the next generation. Therefore organisms have developed the network of conserved mechanisms to survey the protection and precise transfer of the genetic information. Such mechanisms are called checkpoints and they monitor the correct execution of different cell programs. The DNA damage and the replication blocks are surveyed by the conserved Mec1-Rad53 (human ATM/ATR and Chk2, respectively) protein kinase cascade. Mec1 and Rad53 are essential for survival and when activated orchestrate the multiple cellular responses, including the activation of the ribonucleotide reductase (RNR), to the genotoxic stress. RNR is an enzyme producing all four dNTPs - the building blocks of the DNA - and is instrumental for the maintenance both proper concentration and balance of each of dNTPs. The appropriate concentration of the dNTPs should be strictly regulated since inadequate dNTP production can impede many cellular processes and lead to higher mutation rates and genome instability. Hence RNR activity is regulated at many levels, including allosteric and transcriptional regulation and the inhibition at protein level. In our research, we addressed the question of the transcriptional regulation of RNR and the consequences of dNTP malproduction in the terms of the genomic stability. In yeast S. cerevisiae, four genes encode RNR: 2 genes encode a large subunit (RNR1 and RNR3) and 2 genes encode a small subunit (RNR2 and RNR4). All 4 genes are DNA-damage inducible: transcription of RNR2, RNR3 and RNR4 is regulated via Mec1-Rad53-Dun1 pathway by targeting the transcriptional repressor Crt1 (Rfx1) for degradation; on the contrary, RNR1 gene promoter does not contain Crt1-binding sites and is not regulated through the Mec1-Rad53-Dun1 pathway. Instead, we show that intrastrand cross (X)-link recognition protein (Ixr1) is required for the proper transcription of the RNR1 gene and maintenance of the dNTP pools both during unperturbed cell cycle and after the DNA damage. Thus, we identify the novel regulator of the RNR1 transcription. Next, we show that the depletion of dNTP pools negatively affects genome stability in the hypomorphic mec1 mutants: the hyper-recombination phenotype in those mutants correlates with low dNTP levels. By introducing even lower dNTP levels the hyper-recombination increased even further and conversely all the hyper-recombination phenotypes were suppressed by artificial elevation of dNTP levels. In conclusion, we present Ixr1 as a novel regulator of the RNR activity and provide the evidence of role of dNTP concentration in the genome stability.
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