A mechanism for epigenetic control of DNA replication.

DNA replication origins in hyperacetylated euchromatin fire preferentially during early S phase. However, how acetylation controls DNA replication timing is unknown. TICRR/TRESLIN is an essential protein required for the initiation of DNA replication. Here, we report that TICRR physically interacts with the acetyl-histone binding bromodomain (BRD) and extraterminal (BET) proteins BRD2 and BRD4. Abrogation of this interaction impairs TICRR binding to acetylated chromatin and disrupts normal S-phase progression. Our data reveal a novel function for BET proteins and establish the TICRR-BET interaction as a potential mechanism for epigenetic control of DNA replication.

Key roles of autophagosome/endosome maturation mediated by Syntaxin17 in methamphetamine-induced neuronal damage in mice.

BACKGROUND: Autophagic defects are involved in Methamphetamine (Meth)-induced neurotoxicity. Syntaxin 17 (Stx17), a member of the SNARE protein family, participating in several stages of autophagy, including autophagosome-late endosome/lysosome fusion. However, the role of Stx17 and potential mechanisms in autophagic defects induced by Meth remain poorly understood. METHODS: To address the mechanism of Meth-induced cognitive impairment, the adenovirus (AV) and adeno-associated virus (AAV) were injected into the hippocampus for stereotaxis to overexpress Stx17 in vivo to examine the cognitive ability via morris water maze and novel object recognition. In molecular level, the synaptic injury and autophagic defects were evaluated. To address the Meth induced neuronal damage, the epidermal growth factor receptor (EGFR) degradation assay was performed to evaluate the degradability of the "cargos" mediated by Meth, and mechanistically, the maturation of the vesicles, including autophagosomes and endosomes, were validated by the Co-IP and the GTP-agarose affinity isolation assays. RESULTS: Overexpression of Stx17 in the hippocampus markedly rescued the Meth-induced cognitive impairment and synaptic loss. For endosomes, Meth exposure upregulated Rab5 expression and its guanine-nucleotide exchange factor (GEF) (immature endosome), with a commensurate decreased active form of Rab7 (Rab7-GTP) and impeded the binding of Rab7 to CCZ1 (mature endosome); for autophagosomes, Meth treatment elicited a dramatic reduction in the overlap between Stx17 and autophagosomes but increased the colocalization of ATG5 and autophagosomes (immature autophagosomes). After Stx17 overexpression, the Rab7-GTP levels in purified late endosomes were substantially increased in parallel with the elevated mature autophagosomes, facilitating cargo (Aß42, p-tau, and EGFR) degradation in the vesicles, which finally ameliorated Meth-induced synaptic loss and memory deficits in mice. CONCLUSION: Stx17 decrease mediated by Meth contributes to vesicle fusion defects which may ascribe to the immature autophagosomes and endosomes, leading to autophagic dysfunction and finalizes neuronal damage and cognitive impairments. Therefore, targeting Stx17 may be a novel therapeutic strategy for Meth-induced neuronal injury.

The cohesin modifier ESCO2 is stable during DNA replication.

Cohesion between sister chromatids by the cohesin protein complex ensures accurate chromosome segregation and enables recombinational DNA repair. Sister chromatid cohesion is promoted by acetylation of the SMC3 subunit of cohesin by the ESCO2 acetyltransferase, inhibiting cohesin release from chromatin. The interaction of ESCO2 with the DNA replication machinery, in part through PCNA-interacting protein (PIP) motifs in ESCO2, is required for full cohesion establishment. Recent reports have suggested that Cul4-dependent degradation regulates the level of ESCO2 protein following replication. To follow up on these observations, we have characterized ESCO2 stability in Xenopus egg extracts, a cell-free system that recapitulates cohesion establishment in vitro. We found that ESCO2 was stable during DNA replication in this system. Indeed, further challenging the system by inducing DNA damage signaling or increasing the number of nuclei undergoing DNA replication had no significant impact on the stability of ESCO2. In transgenic somatic cell lines, we also did not see evidence of GFP-ESCO2 degradation during S phase of the cell cycle using both flow cytometry and live-cell imaging. We conclude that ESCO2 is stable during DNA replication in both embryonic and somatic cells.

The Arabidopsis transcription factor TCP9 modulates root architectural plasticity, reactive oxygen species-mediated processes, and tolerance to cyst nematode infections.

Infections by root-feeding nematodes have profound effects on root system architecture and consequently shoot growth of host plants. Plants harbor intraspecific variation in their growth responses to belowground biotic stresses by nematodes, but the underlying mechanisms are not well understood. Here, we show that the transcription factor TEOSINTE BRANCHED/CYCLOIDEA/PROLIFERATING CELL FACTOR-9 (TCP9) modulates root system architectural plasticity in Arabidopsis thaliana in response to infections by the endoparasitic cyst nematode Heterodera schachtii. Young seedlings of tcp9 knock-out mutants display a significantly weaker primary root growth inhibition response to cyst nematodes than wild-type Arabidopsis. In older plants, tcp9 reduces the impact of nematode infections on the emergence and growth of secondary roots. Importantly, the altered growth responses by tcp9 are most likely not caused by less biotic stress on the root system, because TCP9 does not affect the number of infections, nematode development, and size of the nematode-induced feeding structures. RNA-sequencing of nematode-infected roots of the tcp9 mutants revealed differential regulation of enzymes involved in reactive oxygen species (ROS) homeostasis and responses to oxidative stress. We also found that root and shoot growth of tcp9 mutants is less sensitive to exogenous hydrogen peroxide and that ROS accumulation in nematode infection sites in these mutants is reduced. Altogether, these observations demonstrate that TCP9 modulates the root system architectural plasticity to nematode infections via ROS-mediated processes. Our study further points at a novel regulatory mechanism contributing to the tolerance of plants to root-feeding nematodes by mitigating the impact of belowground biotic stresses.

Multivalent interaction of ESCO2 with the replication machinery is required for sister chromatid cohesion in vertebrates.

The tethering together of sister chromatids by the cohesin complex ensures their accurate alignment and segregation during cell division. In vertebrates, sister chromatid cohesion requires the activity of the ESCO2 acetyltransferase, which modifies the Smc3 subunit of cohesin. It was shown recently that ESCO2 promotes cohesion through interaction with the MCM replicative helicase. However, ESCO2 does not significantly colocalize with the MCM complex, suggesting there are additional interactions important for ESCO2 function. Here we show that ESCO2 is recruited to replication factories, sites of DNA replication, through interaction with PCNA. We show that ESCO2 contains multiple PCNA-interaction motifs in its N terminus, each of which is essential to its ability to establish cohesion. We propose that multiple PCNA-interaction motifs embedded in a largely flexible and disordered region of the protein underlie the unique ability of ESCO2 to establish cohesion between sister chromatids precisely as they are born during DNA replication.

[Probabilistic risk assessment of dietary exposure to lead among Chongqing residents].

OBJECTIVE: To investigate lead contamination in commercial foods in Chongqing City, and to assess the health risk of dietary lead exposure of residents in Chongqing City. METHODS: Lead concentration data was obtained from the food safety risk monitoring system, which included a total of 2347 lead-containing food samples in 11 categories in Chongqing from 2016 to 2020. Consumption data was derived from the China Health and Nutrition Survey Project in Chongqing in 2018(3 day, 24 h dietary recall survey). The dietary exposure to lead of residents in Chongqing was calculated by the Monte Carlo simulation method and the margin of exposure(MOE) method was used to evaluate the health risk of the population. RESULTS: The average content of lead in 2347 food samples from 11 categories ranged from 0.0328 to 0.0363 mg/kg, with an overall detection rate of 58.5%. For people aged between 3-6, 7-17, 18-59, and ≥ 60 years, the mean dietary lead intakes in Chongqing were 0.935-1.070, 0.600-0.684, 0.367-0.416, 0.369-0.419 µg/(kg·BW·d), respectively; and the high levels of dietary lead exposure(P95) were 1.642-1.852, 1.147-1.299, 0.651-0.729, 0.659-0.740 µg/(kg·BW·d), respectively. MOE values for lead were less than 1 for age groups 3-6 and 7-17 years. Mean MOE values for lead were greater than 1 for ages 18 to 59 and ≥ 60. Cereals and their products, vegetables and their products, and meat and meat products were the main sources of dietary lead exposure, accounting for more than 85% of the total dietary lead exposure. CONCLUSION: There are potential health risks of lead for residents in Chongqing.

Hierarchical Heterostructure Engineering of Layered Double Hydroxides on Nickel Sulfides Heteronanowire Arrays as Efficient Cathode for Alkaline Aqueous Zinc Batteries.

Aqueous alkaline rechargeable nickel-zinc (Ni-Zn) batteries possess great potential for large-scale energy storage systems because of their high output voltage, cheap cost, and intrinsic safety. However, the practical applicability of Ni-Zn batteries has been limited by traditional Ni-based cathodes with low capacity and poor cycle stability. Rational design of electrode structure and composition is highly desired but still significantly challenging. Herein, uniform self-supported hierarchical heterostructure composites interacting NiCo-layered double hydroxide with 1D nickel sulfides heteronanowire rooted on Ni foam (NF\Ni3 S2 /NiS@NiCo-LDH) are successfully developed by a hydrothermal sulfurization-electrodeposition process. The self-supported 3D hierarchical heterostructured composites nanoarray provides abundant reactive sites, rapid ion diffusion channels, and fast electron transfer routes, as well as strong structural stability. More significantly, the strong interfacial charge transfer between Ni3 S2 /NiS heteronanowire and NiCo-LDH effectively modifies the electronic structure of the composites and thereby improving the reaction kinetics. Consequently, the NF\Ni3 S2 /NiS@NiCo-LDH electrode presents a superior capacity of 434.5 mAh g-1 (1.73 mAh cm-2 ) at 3 mA cm-2 . In addition, the fabricated NF\Ni3 S2 /NiS@NiCo-LDH//Zn battery can offer a maximal energy density and power density as large as 556.3 Wh kg-1 and 26.3 kW kg-1 , respectively, as well as an exceptional cycling performance.

Rheumatoid arthritis fibroblast-like synoviocytes maintain tumor-like biological characteristics through ciRS-7-dependent regulation of miR-7.

BACKGROUND: Altered phenotype of Fibroblast-like synoviocyte(FLS) is an important cause of the pathogenesis and progression of rheumatoid arthritis(RA), but the specific mechanism causing this change has not yet been fully explained. The exact mechanism by which the biological properties of FLS change in RA is still unclear. microRNAs (miRNAs) have been shown to affect changes in the biological properties of RA-FLS, but the critical miRNAs remain to be discovered. Thus, we first used miRNA microarray and WGCNA to confirm the RA-FLS miRNA landscape and establish their biological functions via network analyses at the system level, as well as to provide a platform for modulating the overall phenotypic effects of RA-FLS. METHODS: We enrolled a total of 3 patients with RA and 3 healthy participants, constructed a network analysis of via miRNA microarray and RNA-sequencing. Furthermore, the coexpression analyses of miR-7 and ciRS-7 were verified by siRNA transfection, overexpression and qPCR analyses. Finally, we evaluated the effects of adjusting the expression levels of miR-7 and ciRS-7 on RA-FLS, respectively. RESULTS: We identified distinct miRNA features in RA-FLS, including miR-7, which was significantly lower expressed. Furthermore, we discovered the negative regulatory relationship between ciRS-7 and miR-7 in RA-FLS. Finally, we overexpressed miR-7 in RA-FLS and discovered that miR-7 inhibited RA-FLS hyperproliferation, migration, invasion, and apoptosis, whereas ciRS-7 overexpression reversed these effects. CONCLUSIONS: The results indicate that the dysregulation of miR-7 in FLS may be involved in the pathological processes of RA and that ciRS-7 induced the suppression of tumor-like biological characters of RA-FLS via modulation of miR-7. These findings help us understand the essential roles of a regulatory interaction between ciRS-7 and miR-7 mediating disease activity of RA, and will facilitate to develop potential intervention target for RA.

Esco1 and Esco2 regulate distinct cohesin functions during cell cycle progression.

Sister chromatids are tethered together by the cohesin complex from the time they are made until their separation at anaphase. The ability of cohesin to tether sister chromatids together depends on acetylation of its Smc3 subunit by members of the Eco1 family of cohesin acetyltransferases. Vertebrates express two orthologs of Eco1, called Esco1 and Esco2, both of which are capable of modifying Smc3, but their relative contributions to sister chromatid cohesion are unknown. We therefore set out to determine the precise contributions of Esco1 and Esco2 to cohesion in vertebrate cells. Here we show that cohesion establishment is critically dependent upon Esco2. Although most Smc3 acetylation is Esco1 dependent, inactivation of the ESCO1 gene has little effect on mitotic cohesion. The unique ability of Esco2 to promote cohesion is mediated by sequences in the N terminus of the protein. We propose that Esco1-dependent modification of Smc3 regulates almost exclusively the noncohesive activities of cohesin, such as DNA repair, transcriptional control, chromosome loop formation, and/or stabilization. Collectively, our data indicate that Esco1 and Esco2 contribute to distinct and separable activities of cohesin in vertebrate cells.

Sororin is enriched at the central region of synapsed meiotic chromosomes.

During meiotic prophase, cohesin complexes mediate cohesion between sister chromatids and promote pairing and synapsis of homologous chromosomes. Precisely how the activity of cohesin is controlled to promote these events is not fully understood. In metazoans, cohesion establishment between sister chromatids during mitotic divisions is accompanied by recruitment of the cohesion-stabilizing protein Sororin. During somatic cell division cycles, Sororin is recruited in response to DNA replication-dependent modification of the cohesin complex by ESCO acetyltransferases. How Sororin is recruited and acts in meiosis is less clear. Here, we have surveyed the chromosomal localization of Sororin and its relationship to the meiotic cohesins and other chromatin modifiers with the objective of determining how Sororin contributes to meiotic chromosome dynamics. We show that Sororin localizes to the cores of meiotic chromosomes in a manner that is dependent on synapsis and the synaptonemal complex protein SYCP1. In contrast, cohesin, with which Sororin interacts in mitotic cells, shows axial enrichment on meiotic chromosomes even in the absence of synapsis between homologs. Using high-resolution microscopy, we show that Sororin is localized to the central region of the synaptonemal complex. These results indicate that Sororin regulation during meiosis is distinct from its regulation in mitotic cells and may suggest that it interacts with a distinctly different partner to ensure proper chromosome dynamics in meiosis.

[Status of intakes of cereals and tubers among the adults in Chongqing City in 2010-2012].

OBJECTIVE: To analyze the status of consumption of cereal and tuber and its impact on macronutrients in among Chongqing City adults. METHODS: Data were collected from 2010-2012 China National Nutrition and Health Survey Surveillance. Multi-stage cluster random sampling was used to collect data among 1435 adults residents in 4 surveillance sites of China National Nutrition and Health Survey in Chongqing City. The number of male was 639, female was 796. The dietary investigation survey method of24-hour recall for three consecutive days were used to collect information on cereal and tuber intakes. Standardization was performed based on the Chinese population data published by National Statistics Bureau in 2009. The cereal and tuber intakes were calculated after weight adjustment with complex sampling. RESULTS: The average consumption of cereal and tuber was 323. 6 g( d. person) for Chongqing City adults in2010-2012. The proportion of energy from the cereal and tuber were 46. 5% and 2. 9%. The proportion of protein from the cereal was 40. 1%. The residents in urban had a lower intake( 280. 8 g) and proportion of energy of cereal and tuber( 37. 6%) than that of rural( 370. 2 g, 62. 1%), so doalso in the proportion of protein from the cereal( urban 28. 9%, rural 53. 9%). CONCLUSION: The intake of cereal and tuber level of the adult residents of in Chongqing City is lower than the national. The residents in urban had a lower intake than that in rural.

Genistein protects against Aß25-35 induced apoptosis of PC12 cells through JNK signaling and modulation of Bcl-2 family messengers.

BACKGROUND: Deposition of aggregated amyloid beta (Aß) protein is hallmark of Alzheimer's disease, leading to dysfunction and apoptosis of neurons. The isoflavone phytoestrogen compound genistein (Gen) exerts a significant protective effect against Aß25-35 induced neurotoxicity and mitochondrial damage in rat pheochromocytoma (PC12) cells. However, the mechanisms underlying Gen's rescue remain elusive. Therefore we endeavored to research further the molecular mechanisms underlying Gen's inhibition of Aß25-35 induced apoptosis of neurons. RESULTS: We found that Gen dramatically suppressed the activation by Aß25-35 of p-c-Jun N-terminal kinase (p-JNK), and also inhibited the JNK-dependent decreased of Bcl-w and increased of Bim. Furthermore, Gen significantly reduced the cytoplasmic concentrations of cytochrome c and Smac protein as well as caspase-3 activity. Additionally, pretreatment with JNK inhibitor SP600125 effectively suppressed Aß25-35 induced PC12 cell cytotoxicity. CONCLUSION: Taken together, the results suggested that Gen protects PC12 cells from Aß25-35 induced neurotoxicity by interfering with p-JNK activation, thus attenuating the JNK-dependent apoptosis through the mitochondrial pathway. These findings constitute novel insights into the pathway for Aß25-35 toxicity, and the neuroprotective action of Gen.

Zn-induced formation of polymetallic carbonate hydroxide cathodes with high mass loading for high performance aqueous alkaline Zn-based batteries.

Developing high mass loading cathodes with high capacity and durable life cycles is greatly worthwhile and challenging for alkaline aqueous rechargeable Zn-based batteries (AAZBs). Herein, we demonstrate an efficient zinc-induced strategy to rationally develop Zn-Ni-Co carbonate hydroxides/hydroxides heterostructure nanosheet array with an extremely high mass loading of 9.2 mg cm-2 on Ni foam (ZNC/NF) as such a superior cathode for AAZBs. It is discovered that Ni-Co hydroxide nanowires can be transformed into Zn-Ni-Co carbonate hydroxides/hydroxides heterostructure nanosheet with rich defect structures after the introduction of Zn during the synthetic process. The formed heterostructures and rich defect structures can enhance ion and electron transfer efficiency, thus ensuring the excellent electrochemical performance under high loading condition. Consequently, the ZNC/NF//Zn battery shows an outstanding areal capacity of 2.1 mAh cm-2 at 5 mA cm-2, with an ultrahigh energy density of 3.6 mWh cm-2. Moreover, the battery can still retain a high capacity of 0.42 mAh cm-2 after 5000 cycles at 50 mA cm-2, suggesting strong long-term cycling stability. This research enables pave the way for the rational design and manufacture of advanced electrode materials with large mass loadings.

Infusion of GMSCs relieves autoimmune arthritis by suppressing the externalization of neutrophil extracellular traps via PGE2-PKA-ERK axis.

INTRODUCTION: Rheumatoid arthritis (RA) is a systemic autoimmune disease with limited treatment success, characterized by chronic inflammation and progressive cartilage and bone destruction. Accumulating evidence has shown that neutrophil extracellular traps (NETs) released by activated neutrophils are important for initiating and perpetuating synovial inflammation and thereby could be a promising therapeutic target for RA. K/B × N serum transfer-induced arthritis (STIA) is a rapidly developed joint inflammatory model that somehow mimics the inflammatory response in patients with RA. Human gingival-derived mesenchymal stem cells (GMSCs) have been previously shown to possess immunosuppressive effects in arthritis and humanized animal models. However, it is unknown whether GMSCs can manage neutrophils in autoimmune arthritis. OBJECTIVES: To evaluate whether infusion of GMSCs can alleviate RA by regulating neutrophils and NETs formation. If this is so, we will explore the underlying mechanism(s) in an animal model of inflammatory arthritis. METHODS: The effects of GMSCs on RA were assessed by comparing the symptoms of the K/B × N serum transfer-induced arthritis (STIA) model administered either with GMSCs or with control cells. Phenotypes examined included clinical scores, rear ankle thickness, paw swelling, inflammation, synovial cell proliferation, and immune cell frequency. The regulation of GMSCs on NETs was examined through immunofluorescence and immunoblotting in GMSCs-infused STIA mice and in an in vitro co-culture system of neutrophils with GMSCs. The molecular mechanism(s) by which GMSCs regulate NETs was explored both in vitro and in vivo by silencing experiments. RESULTS: We found in this study that adoptive transfer of GMSCs into STIA mice significantly ameliorated experimental arthritis and reduced neutrophil infiltration and NET formation. In vitro studies also showed that GMSCs inhibited the generation of NETs in neutrophils. Subsequent investigations revealed that GMSCs secreted prostaglandin E2 (PGE2) to activate protein kinase A (PKA), which ultimately inhibited the downstream extracellular signal-regulated kinase (ERK) pathway that is essential for NET formation. CONCLUSION: Our results demonstrate that infusion of GMSCs can ameliorate inflammatory arthritis mainly by suppressing NET formation via the PGE2-PKA-ERK signaling pathway. These findings further support the notion that the manipulation of GMSCs is a promising stem cell-based therapy for patients with RA and other autoimmune and inflammatory diseases.

miRNA-148a-containing GMSC-derived EVs modulate Treg/Th17 balance via IKKB/NF-κB pathway and treat a rheumatoid arthritis model.

Mesenchymal stem cells (MSCs) have demonstrated potent immunomodulatory properties that have shown promise in the treatment of autoimmune diseases, including rheumatoid arthritis (RA). However, the inherent heterogeneity of MSCs triggered conflicting therapeutic outcomes, raising safety concerns and limiting their clinical application. This study aimed to investigate the potential of extracellular vesicles derived from human gingival mesenchymal stem cells (GMSC-EVs) as a therapeutic strategy for RA. Through in vivo experiments using an experimental RA model, our results demonstrate that GMSC-EVs selectively homed to inflamed joints and recovered Treg and Th17 cell balance, resulting in the reduction of arthritis progression. Our investigations also uncovered miR-148a-3p as a critical contributor to the Treg/Th17 balance modulation via IKKB/NF-κB signaling orchestrated by GMSC-EVs, which was subsequently validated in a model of human xenograft versus host disease (xGvHD). Furthermore, we successfully developed a humanized animal model by utilizing synovial fibroblasts obtained from patients with RA (RASFs). We found that GMSC-EVs impeded the invasiveness of RASFs and minimized cartilage destruction, indicating their potential therapeutic efficacy in the context of patients with RA. Overall, the unique characteristics - including reduced immunogenicity, simplified administration, and inherent ability to target inflamed tissues - position GMSC-EVs as a viable alternative for RA and other autoimmune diseases.

Heterogeneous ferroptosis susceptibility of macrophages caused by focal iron overload exacerbates rheumatoid arthritis.

Focal iron overload is frequently observed in patients with rheumatoid arthritis (RA), yet its functional significance remains elusive. Herein, we report that iron deposition in lesion aggravates arthritis by inducing macrophage ferroptosis. We show that excessive iron in synovial fluid positively correlates with RA disease severity as does lipid hyperoxidation of focal monocyte/macrophages. Further study reveals high susceptibility to iron induced ferroptosis of the anti-inflammatory macrophages M2, while pro-inflammatory M1 are less affected. Distinct glutathione peroxidase 4 (GPX4) degradation depending on p62/SQSTM1 in the two cell types make great contribution mechanically. Of note, ferroptosis inhibitor liproxstatin-1 (LPX-1) can alleviate the progression of K/BxN serum-transfer induced arthritis (STIA) mice accompanied with increasing M2 macrophages proportion. We thus propose that the heterogeneous ferroptosis susceptibility of macrophage subtypes as well as consequent inflammation and immune disorders are potential biomarkers and therapeutic targets in RA.

Cohesin acetylation promotes sister chromatid cohesion only in association with the replication machinery.

Acetylation of the Smc3 subunit of cohesin is essential to establish functional cohesion between sister chromatids. Smc3 acetylation is catalyzed by members of the Eco family of acetyltransferases, although the mechanism by which acetylation is regulated and how it promotes cohesion are largely unknown. In vertebrates, the cohesin complex binds to chromatin during mitotic exit and is converted to a functional form during or shortly after DNA replication. The conserved proliferating cell nuclear antigen-interacting protein box motif in yeast Eco1 is required for function, and cohesin is acetylated during the S phase. This has led to the notion that acetylation of cohesin is stimulated by interaction of Eco1 with the replication machinery. Here we show that in vertebrates Smc3 acetylation occurs independently of DNA replication. Smc3 is readily acetylated before replication is initiated and after DNA replication is complete. However, we also show that functional acetylation occurs only in association with the replication machinery: disruption of the interaction between XEco2 and proliferating cell nuclear antigen prevents cohesion establishment while having little impact on the overall levels of Smc3 acetylation. These results demonstrate that Smc3 acetylation can occur throughout interphase but that only acetylation in association with the replication fork promotes sister chromatid cohesion. These data reveal how the generation of cohesion is limited to the appropriate time and place during the cell cycle and provide insight into the mechanism by which acetylation ensures cohesion.

Combined genomics and experimental analyses of respiratory characteristics of Shewanella putrefaciens W3-18-1.

It has previously been shown that the Shewanella putrefaciens W3-18-1 strain produces remarkably high current in microbial fuel cells (MFCs) and can form magnetite at 0°C. To explore the underlying mechanisms, we developed a genetic manipulation method by deleting the restriction-modification system genes of the SGI1 (Salmonella genome island 1)-like prophage and analyzed the key genes involved in bacterial respiration. W3-18-1 has less respiratory flexibility than the well-characterized S. oneidensis MR-1 strain, as it possesses fewer cytochrome c genes and lacks the ability to oxidize sulfite or reduce dimethyl sulfoxide (DMSO) and timethylamine oxide (TMAO). W3-18-1 lacks the hydrogen-producing Fe-only hydrogenase, and the hydrogen-oxidizing Ni-Fe hydrogenase genes were split into two separate clusters. Two periplasmic nitrate reductases (NapDAGHB and NapDABC) were functionally redundant in anaerobic growth of W3-18-1 with nitrate as the electron acceptor, though napDABC was not regulated by Crp. Moreover, nitrate respiration started earlier in W3-18-1 than in MR-1 (with NapDAGHB only) under microoxic conditions. These results indicate that Shewanella putrefaciens W3-18-1 is well adapted to habitats with higher oxygen levels. Taken together, the results of this study provide valuable insights into bacterial genome evolution.

Roles of UndA and MtrC of Shewanella putrefaciens W3-18-1 in iron reduction.

BACKGROUND: The completion of genome sequencing in a number of Shewanella species, which are most renowned for their metal reduction capacity, offers a basis for comparative studies. Previous work in Shewanella oneidensis MR-1 has indicated that some genes within a cluster (mtrBAC-omcA-mtrFED) were involved in iron reduction. To explore new features of iron reduction pathways, we experimentally analyzed Shewanella putrefaciens W3-18-1 since its gene cluster is considerably different from that of MR-1 in that the gene cluster encodes only four ORFs. RESULTS: Among the gene cluster, two genes (mtrC and undA) were shown to encode c-type cytochromes. The ΔmtrC deletion mutant revealed significant deficiencies in reducing metals of Fe2O3, α-FeO(OH), ß-FeO(OH), ferric citrate, Mn(IV) and Co(III), but not organic compounds. In contrast, no deficiency of metal reduction was observed in the ΔundA deletion mutant. Nonetheless, undA deletion resulted in progressively slower iron reduction in the absence of mtrC and fitness loss under the iron-using condition, which was indicative of a functional role of UndA in iron reduction. CONCLUSIONS: These results provide physiological and biochemical evidences that UndA and MtrC of Shewanella putrefaciens W3-18-1 are involved in iron reduction.

The intrinsically disordered tail of ESCO1 binds DNA in a charge-dependent manner.

ESCO1 is an acetyltransferase enzyme that regulates chromosome organization and gene expression. It does this by modifying the Smc3 subunit of the Cohesin complex. Although ESCO1 is enriched at the base of chromatin loops in a Cohesin-dependent manner, precisely how it interacts with chromatin is unknown. Here we show that the basic and intrinsically disordered tail of ESCO1 binds DNA with very high affinity, likely through electrostatic interaction. We show that neutralization of positive residues in the N-tail reduces both DNA binding in vitro and association of the enzyme with chromatin in cells. Additionally, disruption of the chromatin state and charge distribution reduces chromatin bound ESCO1. Strikingly, defects in DNA binding do not affect total SMC3 acetylation or sister chromatid cohesion, suggesting that ESCO1-dependent acetylation can occur independently of direct chromatin association. We conclude that the intrinsically disordered tail of ESCO1 binds DNA with both high affinity and turnover, but surprisingly, ESCO1 catalytic activity occurs independently of direct DNA binding by the enzyme.