| 1. |
- Beale, M. A., et al.
(författare)
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Global phylogeny of Treponema pallidum lineages reveals recent expansion and spread of contemporary syphilis
- 2021
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Ingår i: Nature Microbiology. - : Springer Science and Business Media LLC. - 2058-5276. ; 6:12
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Tidskriftsartikel (refereegranskat)abstract
- Syphilis, which is caused by the sexually transmitted bacterium Treponema pallidum subsp. pallidum, has an estimated 6.3 million cases worldwide per annum. In the past ten years, the incidence of syphilis has increased by more than 150% in some high-income countries, but the evolution and epidemiology of the epidemic are poorly understood. To characterize the global population structure of T. pallidum, we assembled a geographically and temporally diverse collection of 726 genomes from 626 clinical and 100 laboratory samples collected in 23 countries. We applied phylogenetic analyses and clustering, and found that the global syphilis population comprises just two deeply branching lineages, Nichols and SS14. Both lineages are currently circulating in 12 of the 23 countries sampled. We subdivided T. p.pallidum into 17 distinct sublineages to provide further phylodynamic resolution. Importantly, two Nichols sublineages have expanded clonally across 9 countries contemporaneously with SS14. Moreover, pairwise genome analyses revealed examples of isolates collected within the last 20 years from 14 different countries that had genetically identical core genomes, which might indicate frequent exchange through international transmission. It is striking that most samples collected before 1983 are phylogenetically distinct from more recently isolated sublineages. Using Bayesian temporal analysis, we detected a population bottleneck occurring during the late 1990s, followed by rapid population expansion in the 2000s that was driven by the dominant T. pallidum sublineages circulating today. This expansion may be linked to changing epidemiology, immune evasion or fitness under antimicrobial selection pressure, since many of the contemporary syphilis lineages we have characterized are resistant to macrolides. Global syphilis prevalence has been increasing. Sequencing and analysis of a global collection of 726 Treponema pallidum samples reveal globally circulating lineages linked to a rapid expansion occurring since the end of the twentieth century.
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| 2. |
- Hewitt, Graeme, et al.
(författare)
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Defective ALC1 nucleosome remodeling confers PARPi sensitization and synthetic lethality with HRD
- 2021
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Ingår i: Molecular Cell. - : Cell Press. - 1097-2765 .- 1097-4164. ; 81:4, s. 767-783.e11
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Tidskriftsartikel (refereegranskat)abstract
- Chromatin is a barrier to efficient DNA repair, as it hinders access and processing of certain DNA lesions. ALC1/CHD1L is a nucleosome-remodeling enzyme that responds to DNA damage, but its precise function in DNA repair remains unknown. Here we report that loss of ALC1 confers sensitivity to PARP inhibitors, methyl-methanesulfonate, and uracil misincorporation, which reflects the need to remodel nucleosomes following base excision by DNA glycosylases but prior to handover to APEX1. Using CRISPR screens, we establish that ALC1 loss is synthetic lethal with homologous recombination deficiency (HRD), which we attribute to chromosome instability caused by unrepaired DNA gaps at replication forks. In the absence of ALC1 or APEX1, incomplete processing of BER intermediates results in post-replicative DNA gaps and a critical dependence on HR for repair. Hence, targeting ALC1 alone or as a PARP inhibitor sensitizer could be employed to augment existing therapeutic strategies for HRD cancers.
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| 3. |
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| 4. |
- Beale, M., et al.
(författare)
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CONTEMPORARY SYPHILIS IS CHARACTERISED BY RAPID GLOBAL SPREAD OF PANDEMIC TREPONEMA PALLIDUM LINEAGES
- 2021
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Ingår i: Sexually Transmitted Infections. - : BMJ Publishing Group Ltd. - 1368-4973 .- 1472-3263. ; 97:Suppl. 1, s. A17-A17
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Background: Syphilis is an important sexually transmitted infection caused by the bacterium Treponema pallidum subspecies pallidum. The last two decades have seen syphilis incidence rise in many high-income countries, yet the evolutionary and epidemiological relationships that underpin this are poorly understood, as is the global T. pallidum population structure.Methods: We assembled a geographically and temporally diverse collection of clinical and laboratory samples, performing direct sequencing on the majority, and combining these with 133 publicly available sequences to compile a dataset comprising 726 T. pallidum genomes. We analysed the resulting genomes using detailed phylogenetic analysis and clustering.Results: We show that syphilis globally can be described by only two deeply branching lineages, Nichols and SS14. We show that both of these lineages can be found circulatingcon currently in 12 of the 23 countries sampled. To provide further phylodynamic resolution we subdivided Treponema pallidum subspecies pallidum into 17 distinct sublineages. Importantly, like SS14, we provide evidence that two Nichols sublineages have expanded clonally across 9 countries contemporaneously with SS14. Moreover, pairwise genome analysis showed that recent isolates circulating in 14 different countries were genetically identical in their core genome to those from other countries, suggesting frequent exchange through international transmission pathways. This contrasts with the majority of samples collected prior to 1983, which are phylogenetically distinct from these more recently isolated sublineages. Bayesian temporal analysis provided evidence of a population bottleneck and decline occurring during the late 1990s, followed by a rapid population expansion a decade later. This was driven by the dominant T. pallidum sublineages circulating today, many of which are resistant to macrolides.Conclusion: Combined we show that the population of contemporary syphilis in high-income countries has undergone a recent and rapid global expansion. This dataset will provide a framework for future characterisation and epidemiological investigation of syphilis populations.
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| 5. |
- Lundgren, Edvin, et al.
(författare)
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Geometry of the valence transition induced surface reconstruction of Sm(0001).
- 2002
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Ingår i: Physical Review Letters. - 1079-7114 .- 0031-9007. ; 88:13, s. 136102-136102
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Tidskriftsartikel (refereegranskat)abstract
- We present a structural determination of the surface reconstruction of the Sm(0001) surface using surface x-ray diffraction, scanning tunneling microscopy, and ab initio calculations. The reconstruction is associated with a large (22%) expansion of the atomic radius for the top monolayer surface Sm atoms. The mechanism driving the surface reconstruction in Sm is unique among all elements and is connected to the strong correlations of the 4f electrons in Sm and the intermediate valence observed in certain Sm compounds. The atoms constituting the top monolayer of Sm(0001) have vastly different chemical properties compared to the layer underneath and behave as if they were an adsorbate of a different chemical species.
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