69 research outputs found

    Discrimination of 5′-terminal start codons by translation initiation factor 3 is mediated by ribosomal protein S1

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    AbstractThe interrelation between ribosomal protein S1 and IF3 in recognition/discrimination of 5′-terminal start codons by 30S ribosomes has been studied using in vitro toeprinting. The study has been performed with two naturally occurring leaderless mRNAs, λ cI and phage r1t rro mRNA, as well as with an artificial leaderless mRNA derived from the E. coli ompA gene. We show that in the absence of S1, IF3 does not discriminate against the authentic 5′-terminal start codon of both cI and rro mRNA. Since IF3 was able to exert its proofreading function for initiator tRNAMetf on 30S ribosomes lacking S1, this observation cannot be attributed to a lack of binding to or action of IF3 on 30S(−S1) ribosomes. In contrast to leaderless mRNAs, ternary complex formation occurs in the presence of IF3 with 30S ribosomes when the start codon is preceded by a short 20-nucleotide 5′-untranslated region containing a canonical Shine and Dalgarno sequence. This suggests that 5′-terminal start codons are recognised by IF3 as non-standard because of the lack of 16S rRNA-mRNA contacts

    MazF activation promotes translational heterogeneity of the grcA mRNA in Escherichia coli populations

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    Bacteria adapt to adverse environmental conditions by altering gene expression patterns. Recently, a novel stress adaptation mechanism has been described that allows Escherichia coli to alter gene expression at the post-transcriptional level. The key player in this regulatory pathway is the endoribonuclease MazF, the toxin component of the toxin-antitoxin module mazEF that is triggered by various stressful conditions. In general, MazF degrades the majority of transcripts by cleaving at ACA sites, which results in the retardation of bacterial growth. Furthermore, MazF can process a small subset of mRNAs and render them leaderless by removing their ribosome binding site. MazF concomitantly modifies ribosomes, making them selective for the translation of leaderless mRNAs. In this study, we employed fluorescent reporter-systems to investigate mazEF expression during stressful conditions, and to infer consequences of the mRNA processing mediated by MazF on gene expression at the single-cell level. Our results suggest that mazEF transcription is maintained at low levels in single cells encountering adverse conditions, such as antibiotic stress or amino acid starvation. Moreover, using the grcA mRNA as a model for MazF-mediated mRNA processing, we found that MazF activation promotes heterogeneity in the grcA reporter expression, resulting in a subpopulation of cells with increased levels of GrcA reporter protein

    In vitro analysis of the interaction between the small RNA SR1 and its primary target ahrC mRNA

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    Small regulatory RNAs (sRNAs) from bacterial chromosomes became the focus of research over the past five years. However, relatively little is known in terms of structural requirements, kinetics of interaction with their targets and degradation in contrast to well-studied plasmid-encoded antisense RNAs. Here, we present a detailed in vitro analysis of SR1, a sRNA of Bacillus subtilis that is involved in regulation of arginine catabolism by basepairing with its target, ahrC mRNA. The secondary structures of SR1 species of different lengths and of the SR1/ahrC RNA complex were determined and functional segments required for complex formation narrowed down. The initial contact between SR1 and its target was shown to involve the 5′ part of the SR1 terminator stem and a region 100 bp downstream from the ahrC transcriptional start site. Toeprinting studies and secondary structure probing of the ahrC/SR1 complex indicated that SR1 inhibits translation initiation by inducing structural changes downstream from the ahrC RBS. Furthermore, it was demonstrated that Hfq, which binds both SR1 and ahrC RNA was not required to promote ahrC/SR1 complex formation but to enable the translation of ahrC mRNA. The intracellular concentrations of SR1 were calculated under different growth conditions

    Both RNase E and RNase III control the stability of sodB mRNA upon translational inhibition by the small regulatory RNA RyhB

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    Previous work has demonstrated that iron-dependent variations in the steady-state concentration and translatability of sodB mRNA are modulated by the small regulatory RNA RyhB, the RNA chaperone Hfq and RNase E. In agreement with the proposed role of RNase E, we found that the decay of sodB mRNA is retarded upon inactivation of RNase E in vivo, and that the enzyme cleaves within the sodB 5′-untranslated region (5′-UTR) in vitro, thereby removing the 5′ stem–loop structure that facilitates Hfq and ribosome binding. Moreover, RNase E cleavage can also occur at a cryptic site that becomes available upon sodB 5′-UTR/RyhB base pairing. We show that while playing an important role in facilitating the interaction of RyhB with sodB mRNA, Hfq is not tightly retained by the RyhB–sodB mRNA complex and can be released from it through interaction with other RNAs added in trans. Unlike turnover of sodB mRNA, RyhB decay in vivo is mainly dependent on RNase III, and its cleavage by RNase III in vitro is facilitated upon base pairing with the sodB 5′-UTR. These data are discussed in terms of a model, which accounts for the observed roles of RNase E and RNase III in sodB mRNA turnover

    Autoregulation of mazEF expression underlies growth heterogeneity in bacterial populations

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    The MazF toxin sequence-specifically cleaves single-stranded RNA upon various stressful conditions, and it is activated as a part of the mazEF toxin–antitoxin module in Escherichia coli. Although autoregulation of mazEF expression through the MazE antitoxin-dependent transcriptional repression has been biochemically characterized, less is known about post-transcriptional autoregulation, as well as how both of these autoregulatory features affect growth of single cells during conditions that promote MazF production. Here, we demonstrate post-transcriptional autoregulation of mazF expression dynamics by MazF cleaving its own transcript. Single-cell analyses of bacterial populations during ectopic MazF production indicated that two-level autoregulation of mazEF expression influences cell-to-cell growth rate heterogeneity. The increase in growth rate heterogeneity is governed by the MazE antitoxin, and tuned by the MazF-dependent mazF mRNA cleavage. Also, both autoregulatory features grant rapid exit from the stress caused by mazF overexpression. Time-lapse microscopy revealed that MazF-mediated cleavage of mazF mRNA leads to increased temporal variability in length of individual cells during ectopic mazF overexpression, as explained by a stochastic model indicating that mazEF mRNA cleavage underlies temporal fluctuations in MazF levels during stress

    The NORDeHEALTH 2022 Patient Survey: Cross-Sectional Study of National Patient Portal Users in Norway, Sweden, Finland, and Estonia

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    Background: Although many surveys have been conducted on patients accessing their own health records in recent years, there is a limited amount of nationwide cross-country data available on patients’ views and preferences. To address this gap, an international survey of patient users was conducted in the Nordic eHealth project, NORDeHEALTH. Objective: We aimed to investigate the sociodemographic characteristics and experiences of patients who accessed their electronic health records (EHRs) through national patient portals in Norway, Sweden, Finland, and Estonia. Methods: A cross-sectional web-based survey was distributed using the national online health portals. The target participants were patients who accessed the national patient portals at the start of 2022 and who were aged ≥15 years. The survey included a mixture of close-ended and free-text questions about participant sociodemographics, usability experience, experiences with health care and the EHR, reasons for reading health records online, experience with errors, omissions and offense, opinions about security and privacy, and the usefulness of portal functions. In this paper, we summarized the data on participant demographics, past experience with health care, and the patient portal through descriptive statistics. Results: In total, 29,334 users completed the survey, of which 9503 (32.40%) were from Norway, 13,008 (44.35%) from Sweden, 4713 (16.07%) from Finland, and 2104 (7.17%) from Estonia. National samples were comparable according to reported gender, with about two-thirds identifying as women (19,904/29,302, 67.93%). Age distributions were similar across the countries, but Finland had older users while Estonia had younger users. The highest attained education and presence of health care education varied among the national samples. In all 4 countries, patients most commonly rated their health as “fair” (11,279/29,302, 38.48%). In Estonia, participants were more often inclined to rate their health positively, whereas Norway and Sweden had the highest proportion of negative health ratings. Across the whole sample, most patients received some care in the last 2 years (25,318/29,254, 86.55%). Mental health care was more common (6214/29,254, 21.24%) than oncological care (3664/29,254, 12.52%). Overall, most patients had accessed their health record “2 to 9 times” (11,546/29,306, 39.4%), with the most frequent users residing in Sweden, where about one-third of patients accessed it “more than 20 times” (4571/13,008, 35.14%). Conclusions: This is the first large-scale international survey to compare patient users’ sociodemographics and experiences with accessing their EHRs. Although the countries are in close geographic proximity and demonstrate similar advancements in giving their residents online records access, patient users in this survey differed. We will continue to investigate patients’ experiences and opinions about national patient-accessible EHRs through focused analyses of the national and combined data sets from the NORDeHEALTH 2022 Patient Survey

    Disease-specific molecular events in cortical multiple sclerosis lesions

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    Cortical lesions constitute an important part of multiple sclerosis pathology. Although inflammation appears to play a role in their formation, the mechanisms leading to demyelination and neurodegeneration are poorly understood. We aimed to identify some of these mechanisms by combining gene expression studies with neuropathological analysis. In our study, we showed that the combination of inflammation, plaque-like primary demyelination and neurodegeneration in the cortex is specific for multiple sclerosis and is not seen in other chronic inflammatory diseases mediated by CD8-positive T cells (Rasmussen’s encephalitis), B cells (B cell lymphoma) or complex chronic inflammation (tuberculous meningitis, luetic meningitis or chronic purulent meningitis). In addition, we performed genome-wide microarray analysis comparing micro-dissected active cortical multiple sclerosis lesions with those of tuberculous meningitis (inflammatory control), Alzheimer’s disease (neurodegenerative control) and with cortices of age-matched controls. More than 80% of the identified multiple sclerosis-specific genes were related to T cell-mediated inflammation, microglia activation, oxidative injury, DNA damage and repair, remyelination and regenerative processes. Finally, we confirmed by immunohistochemistry that oxidative damage in cortical multiple sclerosis lesions is associated with oligodendrocyte and neuronal injury, the latter also affecting axons and dendrites. Our study provides new insights into the complex mechanisms of neurodegeneration and regeneration in the cortex of patients with multiple sclerosis

    The importance of the altricial – precocial spectrum for social complexity in mammals and birds:A review

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    Various types of long-term stable relationships that individuals uphold, including cooperation and competition between group members, define social complexity in vertebrates. Numerous life history, physiological and cognitive traits have been shown to affect, or to be affected by, such social relationships. As such, differences in developmental modes, i.e. the ‘altricial-precocial’ spectrum, may play an important role in understanding the interspecific variation in occurrence of social interactions, but to what extent this is the case is unclear because the role of the developmental mode has not been studied directly in across-species studies of sociality. In other words, although there are studies on the effects of developmental mode on brain size, on the effects of brain size on cognition, and on the effects of cognition on social complexity, there are no studies directly investigating the link between developmental mode and social complexity. This is surprising because developmental differences play a significant role in the evolution of, for example, brain size, which is in turn considered an essential building block with respect to social complexity. Here, we compiled an overview of studies on various aspects of the complexity of social systems in altricial and precocial mammals and birds. Although systematic studies are scarce and do not allow for a quantitative comparison, we show that several forms of social relationships and cognitive abilities occur in species along the entire developmental spectrum. Based on the existing evidence it seems that differences in developmental modes play a minor role in whether or not individuals or species are able to meet the cognitive capabilities and requirements for maintaining complex social relationships. Given the scarcity of comparative studies and potential subtle differences, however, we suggest that future studies should consider developmental differences to determine whether our finding is general or whether some of the vast variation in social complexity across species can be explained by developmental mode. This would allow a more detailed assessment of the relative importance of developmental mode in the evolution of vertebrate social systems

    Translational autocontrol of the Escherichia coli hfq RNA chaperone gene

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    The conserved bacterial RNA chaperone Hfq has been shown to play an important role in post-transcriptional regulation. Here, we demonstrate that Hfq synthesis is autoregulated at the translational level. We have mapped two Hfq binding sites in the 5′-untranslated region of hfq mRNA and show that Hfq binding inhibits formation of the translation initiation complex. In vitro translation and in vivo studies further revealed that Hfq binding to both sites is required for efficient translational repression of hfq mRNA
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