7,8-Dihydro-8-oxoadenine, a highly mutagenic adduct, is repaired by Escherichia coli and human mismatch-specific uracil/thymine-DNA glycosylases

Hydroxyl radicals predominantly react with the C(8) of purines forming 7,8-dihydro-8-oxoguanine (8oxoG) and 7,8-dihydro-8-oxoadenine (8oxoA) adducts, which are highly mutagenic in mammalian cells. The majority of oxidized DNA bases are removed by DNA glycosylases in the base excision repair pathway. Here, we report for the first time that human thymine-DNA glycosylase (hTDG) and Escherichia coli mismatch-specific uracil-DNA glycosylase (MUG) can remove 8oxoA from 8oxoA*T, 8oxoA*G and 8oxoA*C pairs. Comparison of the kinetic parameters of the reaction indicates that full-length hTDG excises 8oxoA, 3,N(4)-ethenocytosine (epsilonC) and T with similar efficiency (k(max) = 0.35, 0.36 and 0.16 min(-1), respectively) and is more proficient as compared with its bacterial homologue MUG. The N-terminal domain of the hTDG protein is essential for 8oxoA-DNA glycosylase activity, but not for epsilonC repair. Interestingly, the TDG status had little or no effect on the proliferation rate of mouse embryonic fibroblasts after exposure to gamma-irradiation. Nevertheless, using whole cell-free extracts from the DNA glycosylase-deficient murine embryonic fibroblasts and E. coli, we demonstrate that the excision of 8oxoA from 8oxoA*T and 8oxoA*G has an absolute requirement for TDG and MUG, respectively. The data establish that MUG and TDG can counteract the genotoxic effects of 8oxoA residues in vivo

Aberrant repair initiated by mismatch-specific thymine-DNA glycosylases provides a mechanism for the mutational bias observed in CpG islands

The human thymine-DNA glycosylase (TDG) initiates the base excision repair (BER) pathway to remove spontaneous and induced DNA base damage. It was first biochemically characterized for its ability to remove T mispaired with G in CpG context. TDG is involved in the epigenetic regulation of gene expressions by protecting CpG-rich promoters from de novo DNA methylation. Here we demonstrate that TDG initiates aberrant repair by excising T when it is paired with a damaged adenine residue in DNA duplex. TDG targets the non-damaged DNA strand and efficiently excises T opposite of hypoxanthine (Hx), 1,N6-ethenoadenine, 7,8-dihydro-8-oxoadenine and abasic site in TpG/CpX context, where X is a modified residue. In vitro reconstitution of BER with duplex DNA containing Hx•T pair and TDG results in incorporation of cytosine across Hx. Furthermore, analysis of the mutation spectra inferred from single nucleotide polymorphisms in human population revealed a highly biased mutation pattern within CpG islands (CGIs), with enhanced mutation rate at CpA and TpG sites. These findings demonstrate that under experimental conditions used TDG catalyzes sequence context-dependent aberrant removal of thymine, which results in TpG, CpA→CpGmutations, thus providing a plausible mechanism for the putative evolutionary origin of the CGIs in mammalian genomes

Autophagy in dental tissues: a double-edged sword

Biotechnology and Biological Sciences Research Council [BB/L02392X/1]SCI(E)PubMedEDITORIAL [email protected]

Frizzled-1 receptor regulates adult hippocampal neurogenesis

Indexación: Web of Science; Scopus.Background: In the adult hippocampus new neurons are continuously generated from neural stem cells (NSCs) present at the subgranular zone of the dentate gyrus. This process is controlled by Wnt signaling, which plays a complex role in regulating multiple steps of neurogenesis including maintenance, proliferation and differentiation of progenitor cells and the development of newborn neurons. Differential effects of Wnt signaling during progression of neurogenesis could be mediated by cell-type specific expression of Wnt receptors. Here we studied the potential role of Frizzled-1 (FZD1) receptor in adult hippocampal neurogenesis. Results: In the adult dentate gyrus, we determined that FZD1 is highly expressed in NSCs, neural progenitors and immature neurons. Accordingly, FZD1 is expressed in cultured adult hippocampal progenitors isolated from mouse brain. To evaluate the role of this receptor in vivo we targeted FZD1 in newborn cells using retroviral-mediated RNA interference. FZD1 knockdown resulted in a marked decrease in the differentiation of newborn cells into neurons and increased the generation of astrocytes, suggesting a regulatory role for the receptor in cell fate commitment. In addition, FZD1 knockdown induced an extended migration of adult-born neurons within the granule cell layer. However, no differences were observed in total dendritic length and dendritic arbor complexity between control and FZD1-deficient newborn neurons. Conclusions: Our results show that FZD1 regulates specific stages of adult hippocampal neurogenesis, being required for neuronal differentiation and positioning of newborn neurons into the granule cell layer, but not for morphological development of adult-born granule neurons.https://molecularbrain.biomedcentral.com/articles/10.1186/s13041-016-0209-

A framework to develop semiautomated surveillance of surgical site infections: An international multicenter study

Objective: Automated surveillance of healthcare-associated infections reduces workload and improves standardization, but it has not yet been adopted widely. In this study, we assessed the performance and feasibility of an easy implementable framework to develop algorithms for semiautomated surveillance of deep incisional and organ-space surgical site infections (SSIs) after orthopedic, cardiac, and colon surgeries. Design: Retrospective cohort study in multiple countries. Methods: European hospitals were recruited and selected based on the availability of manual SSI surveillance data from 2012 onward (reference standard) and on the ability to extract relevant data from electronic health records. A questionnaire on local manual surveillance and clinical practices was administered to participating hospitals, and the information collected was used to pre-emptively design semiautomated surveillance algorithms standardized for multiple hospitals and for center-specific application. Algorithm sensitivity, positive predictive value, and reduction of manual charts requiring review were calculated. Reasons for misclassification were explored using discrepancy analyses. Results: The study included 3 hospitals, in the Netherlands, France, and Spain. Classification algorithms were developed to indicate procedures with a high probability of SSI. Components concerned microbiology, prolonged length of stay or readmission, and reinterventions. Antibiotics and radiology ordering were optional. In total, 4,770 orthopedic procedures, 5,047 cardiac procedures, and 3,906 colon procedures were analyzed. Across hospitals, standardized algorithm sensitivity ranged between 82% and 100% for orthopedic surgery, between 67% and 100% for cardiac surgery, and between 84% and 100% for colon surgery, with 72%-98% workload reduction. Center-specific algorithms had lower sensitivity. Conclusions: Using this framework, algorithms for semiautomated surveillance of SSI can be successfully developed. The high performance of standardized algorithms holds promise for large-scale standardization

The human DNA glycosylases NEIL1 and NEIL3 excise psoralen-induced DNA-DNA cross-links in a four-stranded DNA structure

Interstrand cross-links (ICLs) are highly cytotoxic DNA lesions that block DNA replication and transcription by preventing strand separation. Previously, we demonstrated that the bacterial and human DNA glycosylases Nei and NEIL1 excise unhooked psoralen-derived ICLs in three-stranded DNA via hydrolysis of the glycosidic bond between the crosslinked base and deoxyribose sugar. Furthermore, NEIL3 from Xenopus laevis has been shown to cleave psoralen- and abasic site-induced ICLs in Xenopus egg extracts. Here we report that human NEIL3 cleaves psoralen-induced DNA-DNA cross-links in three-stranded and four-stranded DNA substrates to generate unhooked DNA fragments containing either an abasic site or a psoralen-thymine monoadduct. Furthermore, while Nei and NEIL1 also cleave a psoralen-induced four-stranded DNA substrate to generate two unhooked DNA duplexes with a nick, NEIL3 targets both DNA strands in the ICL without generating single-strand breaks. The DNA substrate specificities of these Nei-like enzymes imply the occurrence of long uninterrupted three- and four-stranded crosslinked DNA-DNA structures that may originate in vivo from DNA replication fork bypass of an ICL. In conclusion, the Nei-like DNA glycosylases unhook psoralen-derived ICLs in various DNA structures via a genuine repair mechanism in which complex DNA lesions can be removed without generation of highly toxic double-strand breaks

Scientific, Technical and Economic Committee for Fisheries (STECF) - Stock assessments in the Western Mediterranean Sea (STECF 23-09)

801 pagesCommission Decision of 25 February 2016 setting up a Scientific, Technical and Economic Committee for Fisheries, C(2016) 1084, OJ C 74, 26.2.2016, p. 4–10. The Commission may consult the group on any matter relating to marine and fisheries biology, fishing gear technology, fisheries economics, fisheries governance, ecosystem effects of fisheries, aquaculture or similar disciplines This report documents the outcomes of STECF Expert Working Group 23-09: 2023 stock assessments of demersal stocks in the Western Mediterranean Sea from the meeting held in hybrid mode from 4th to 10th September 2023. A total of 20 fish stocks considered. Nine stocks were evaluated by means of a statistical catch at age (SCAA) model (a4a). Due to the lack of survey information in 2022, five stocks were evaluated through a catch weight projection and short-term forecast. The methodological approach is described in the last part of this Executive Summary, and in the Report. In 2022, index-based advice was given for three stocks (ARA8-9-10-11 and NEP11 on two years basis while for MUT 10 just for one year), and they were re-evaluated by EWG 23-09. The advice for ARA8-9-10-11 and NEP11 have been confirmed while for MUT 10 the missing index information led the group to consider downgrading the advice from an index-based one to a catch only advice approach (ICES Category 5). Two stocks for which the index-based advice provided in 2021 (2 years advice) have been evaluated again looking for a plausible fully analytical assessment. None of the model setting tried was able to provide acceptable results, therefore a biomass index-based advice is given again. The content of the report gives the STECF terms of reference; the basis of the evaluations; assessments, reference point calculations; summaries of state of stock and advised catch or F based on either the MSY approach for assessed stocks and category 3 and 5 based advice for those without assessments. The report contains the full stock assessment reports, the exploration of assessments and category 3 and 5 evaluations for the remaining stocks. The report also contains the STECF observations and conclusions on the assessment report. These conclusions come from the STECF mini plenary meeting October 2023With the institutional support of the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S)Peer reviewe

GABAB Receptor Subunit GB1 at the Cell Surface Independently Activates ERK1/2 through IGF-1R Transactivation

BACKGROUND: Functional GABA(B) receptor is believed to require hetero-dimerization between GABA(B1) (GB1) and GABA(B2) (GB2) subunits. The GB1 extracellular domain is required for ligand binding, and the GB2 trans-membrane domain is responsible for coupling to G proteins. Atypical GABA(B) receptor responses observed in GB2-deficient mice suggested that GB1 may have activity in the absence of GB2. However the underlying mechanisms remain poorly characterized. METHODOLOGY/PRINCIPAL FINDINGS: Here, by using cells overexpressing a GB1 mutant (GB1asa) with the ability to translocate to the cell surface in the absence of GB2, we show that GABA(B) receptor agonists, such as GABA and Baclofen, can induce ERK1/2 phosphorylation in the absence of GB2. Furthermore, we demonstrate that GB1asa induces ERK1/2 phosphorylation through Gi/o proteins and PLC dependent IGF-1R transactivation. CONCLUSIONS/SIGNIFICANCE: Our data suggest that GB1 may form a functional receptor at the cell surface in the absence of GB2

Functioning of the dimeric GABA(B) receptor extracellular domain revealed by glycan wedge scanning

The G-protein-coupled receptor (GPCR) activated by the neurotransmitter GABA is made up of two subunits, GABA(B1) and GABA(B2). GABA(B1) binds agonists, whereas GABA(B2) is required for trafficking GABA(B1) to the cell surface, increasing agonist affinity to GABA(B1), and activating associated G proteins. These subunits each comprise two domains, a Venus flytrap domain (VFT) and a heptahelical transmembrane domain (7TM). How agonist binding to the GABA(B1) VFT leads to GABA(B2) 7TM activation remains unknown. Here, we used a glycan wedge scanning approach to investigate how the GABA(B) VFT dimer controls receptor activity. We first identified the dimerization interface using a bioinformatics approach and then showed that introducing an N-glycan at this interface prevents the association of the two subunits and abolishes all activities of GABA(B2), including agonist activation of the G protein. We also identified a second region in the VFT where insertion of an N-glycan does not prevent dimerization, but blocks agonist activation of the receptor. These data provide new insight into the function of this prototypical GPCR and demonstrate that a change in the dimerization interface is required for receptor activation