Growth Repression Research Articles

PDX1.1-dependent biosynthesis of vitamin B6 protects roots from ammonium-induced oxidative stress

Despite serving as a major inorganic nitrogen source for plants, ammonium causes toxicity at elevated concentrations, inhibiting root elongation early on. While previous studies have shown that ammonium-inhibited root development relates to ammonium uptake and formation of reactive oxygen species (ROS) in roots, it remains unclear about the mechanisms underlying the repression of root growth and how plants cope with this inhibitory effect of ammonium. In this study, we demonstrate that ammonium-induced apoplastic acidification co-localizes with Fe precipitation and hydrogen peroxide (H2O2) accumulation along the stele of the elongation and differentiation zone in root tips, indicating Fe-dependent ROS formation. By screening ammonium sensitivity in T-DNA insertion lines of ammonium-responsive genes, we identified PDX1.1, which is upregulated by ammonium in the root stele and whose product catalyzes de novo biosynthesis of vitamin B6. Root growth of pdx1.1 mutants is hypersensitive to ammonium, while chemical complementation or overexpression of PDX1.1 restores root elongation. This salvage strategy requires non-phosphorylated forms of vitamin B6 that are able to quench ROS and rescue root growth from ammonium inhibition. Collectively, these results suggest that PDX1.1-mediated synthesis of non-phosphorylated B6 vitamers acts as a primary strategy to protect roots from ammonium-dependent ROS formation.

The Candida albicans Cdk8-dependent phosphoproteome reveals repression of hyphal growth through a Flo8-dependent pathway.

Ssn3, also known as Cdk8, is a member of the four protein Cdk8 submodule within the multi-subunit Mediator complex involved in the co-regulation of transcription. In Candida albicans, the loss of Ssn3 kinase activity affects multiple phenotypes including cellular morphology, metabolism, nutrient acquisition, immune cell interactions, and drug resistance. In these studies, we generated a strain in which Ssn3 was replaced with a functional variant of Ssn3 that can be rapidly and selectively inhibited by the ATP analog 3-MB-PP1. Consistent with ssn3 null mutant and kinase dead phenotypes, inhibition of Ssn3 kinase activity promoted hypha formation. Furthermore, the increased expression of hypha-specific genes was the strongest transcriptional signal upon inhibition of Ssn3 in transcriptomics analyses. Rapid inactivation of Ssn3 was used for phosphoproteomic studies performed to identify Ssn3 kinase substrates associated with filamentation potential. Both previously validated and novel Ssn3 targets were identified. Protein phosphorylation sites that were reduced specifically upon Ssn3 inhibition included two sites in Flo8 which is a transcription factor known to positively regulate C. albicans morphology. Mutation of the two Flo8 phosphosites (threonine 589 and serine 620) was sufficient to increase Flo8-HA levels and Flo8 dependent transcriptional and morphological changes, suggesting that Ssn3 kinase activity negatively regulates Flo8.Under embedded conditions, when ssn3Δ/Δ and efg1Δ/Δ mutants were hyperfilamentous, FLO8 was essential for hypha formation. Previous work has also shown that loss of Ssn3 activity leads to increased alkalinization of medium with amino acids. Here, we show that the ssn3Δ/Δ medium alkalinization phenotype, which is dependent on STP2, a transcription factor involved in amino acid utilization, also requires FLO8 and EFG1. Together, these data show that Ssn3 activity can modulate Flo8 and its direct and indirect interactions in different ways, and underscores the potential importance of considering Ssn3 function in the control of transcription factor activities.

LSM12 facilitates the progression of colorectal cancer by activating the WNT/CTNNB1 signaling pathway.

Aberrant activation of the WNT signaling pathway is a joint event in colorectal cancer (CRC), but the molecular mechanism is still unclear. Recently, RNA-splicing factor LSM12 (like-Sm protein 12) is highly expressed in CRC tissues. This study aimed to verify whether LSM12 is involved in regulating CRC progression via regulating the WNT signaling pathway. Here, we found that LSM12 is highly expressed in CRC patient-derived tissues and cells. LSM12 is involved in the proliferation, invasion, and apoptosis of CRC cells, similar to the function of WNT signaling in CRC. Furthermore, protein interaction simulation and biochemical experiments proved that LSM12 directly binds to CTNNB1 (also known as β-Catenin) and regulates its protein stability to affect the CTTNB1-LEF1-TCF1 transcriptional complex formation and the associated WNT downstream signaling pathway. LSM12 depletion in CRC cells decreased the in vivo tumor growth through repression of cancer cell growth and acceleration of cancer cell apoptosis. Taken together, we suggest that the high expression of LSM12 is a novel factor leading to aberrant WNT signaling activation, and that strategies targeting this molecular mechanism may contribute to developing a new therapeutic method for CRC.

Role of substrate availability in the growth of Campylobacter co-cultured with extended spectrum beta-lactamase-producing Escherichia coli in Bolton broth

It is well-established that Extended-spectrum beta-lactamase-producing (ESBL-) Escherichia coli challenge reliable detection of campylobacters during enrichment in Bolton broth (BB) following ISO 10272-1:2017. The overgrowth of Campylobacter by ESBL-E. coli in the enrichment medium BB can lead to false-negative detection outcomes, but the cause for the growth suppression is yet unknown. A plausible reason could be the competition-induced lack of certain growth substrates. Therefore, this study aimed to investigate whether campylobacters and ESBL-E. coli compete for the same medium components and whether this is the cause for the observed growth repression. The availability of possible growth substrates in BB was determined and changes in their extracellular concentration were measured over time during mono-culture enrichment of C. jejuni, C. coli or ESBL-E. coli as well as in co-culture enrichments of campylobacters and ESBL-E. coli. Comparative analysis showed lactate and fumarate utilization by C. jejuni and C. coli exclusively, whereas ESBL-E. coli rapidly consumed asparagine, glutamine/arginine, lysine, threonine, tryptophan, pyruvate, glycerol, cellobiose, and glucose. Both campylobacters and ESBL-E. coli utilized aspartate, serine, formate, a-ketoglutarate and malate. Trends in compound utilization were similar for C. jejuni and C. coli and trends in compound utilization were rather comparable during enrichment of reference and freeze-stressed campylobacters. Since final cell densities of C. jejuni and C. coli in co-cultures were not enhanced by the addition of surplus l-serine and final cell densities were similar in fresh and spent medium, growth suppression seems not to be caused by a lack of substrates or production of inhibitory compounds. We hypothesized that oxygen availability was limiting growth in co-cultures. Higher oxygen availability increased the competitive fitness of C. jejuni 81-176 in co-culture with ESBL-E. coli in duplicate experiments, as cell concentrations in stationary phase were similar to those without competition. This could indicate the critical role of oxygen availability during the growth of Campylobacter and offers potential for further improvement of Campylobacter spp. enrichment efficacy.

Regulatory circuits involving bud dormancy factor PpeDAM6

DORMANCY-ASSOCIATED MADS-BOX (DAM) genes have recently emerged as key potential regulators of the dormancy cycle and climate adaptation in perennial species. Particularly, PpeDAM6 has been proposed to act as a major repressor of bud dormancy release and bud break in peach (Prunus persica). PpeDAM6 expression is downregulated concomitantly with the perception of a given genotype-dependent accumulation of winter chilling time, and the coincident enrichment in H3K27me3 chromatin modification at a specific genomic region. We have identified three peach BASIC PENTACYSTEINE PROTEINs (PpeBPCs) interacting with two GA-repeat motifs present in this H3K27me3-enriched region. Moreover, PpeBPC1 represses PpeDAM6 promoter activity by transient expression experiments. On the other hand, the heterologous overexpression of PpeDAM6 in European plum (Prunus domestica) alters plant vegetative growth, resulting in dwarf plants tending toward shoot meristem collapse. These alterations in vegetative growth of transgenic lines associate with impaired hormone homeostasis due to the modulation of genes involved in jasmonic acid, cytokinin, abscisic acid, and gibberellin pathways, and the downregulation of shoot meristem factors, specifically in transgenic leaf and apical tissues. The expression of many of these genes is also modified in flower buds of peach concomitantly with PpeDAM6 downregulation, which suggests a role of hormone homeostasis mechanisms in PpeDAM6-dependent maintenance of floral bud dormancy and growth repression.

BTB and CNC homology 1 (Bach1) induces lung cancer stem cell phenotypes by stimulating CD44 expression

BackgroundGrowing evidence suggests that cancer stem cells (CSCs) are responsible for cancer initiation in tumors. Bach1 has been identified to contribute to several tumor progression, including lung cancer. The role of Bach1 in CSCs remains poorly known. Therefore, the function of Bach1 on lung CSCs was focused currently.MethodsThe expression of Bach1, CD133, CD44, Sox2, Nanog and Oct4 mRNA was assessed using Real-Time Quantitative Reverse Transcription PCR (RT-qPCR). Protein expression of Bach1, CD133, CD44, Sox2, Nanog, Oct4, p53, BCL2, BAX, p-p38, p-AKT1, c-Fos and c-Jun protein was analyzed by western blotting. 5-ethynyl-29-deoxyuridine (EdU), colony formation, Flow cytometry analysis and transwell invasion assay were carried out to analyze lung cancer cell proliferation, apoptosis and invasion respectively. Tumor sphere formation assay was utilized to evaluate spheroid capacity. Flow cytometry analysis was carried out to isolate CD133 or CD44 positive lung cancer cells. The relationship between Bach1 and CD44 was verified using ChIP-qPCR and dual-luciferase reporter assay. Xenograft tumor tissues were collected for hematoxylin and eosin (HE) staining and IHC analysis to evaluate histology and Ki-67.ResultsThe ratio of CD44 + CSCs from A549 and SPC-A1 cells were significantly enriched. Tumor growth of CD44 + CSCs was obviously suppressed in vivo compared to CD44− CSCs. Bach1 expression was obviously increased in CD44 + CSCs. Then, via using the in vitro experiment, it was observed that CSCs proliferation and invasion were greatly reduced by the down-regulation of Bach1 while cell apoptosis was triggered by knockdown of Bach1. Loss of Bach1 was able to repress tumor-sphere formation and tumor-initiating CSC markers. A repression of CSCs growth and metastasis of shRNA-Bach1 was confirmed using xenograft models and caudal vein injection. The direct interaction between Bach1 and CD44 was confirmed by ChIP-qPCR and dual-luciferase reporter assay. Furthermore, mitogen-activated protein kinases (MAPK) signaling pathway was selected and we proved the effects of Bach1 on lung CSCs were associated with the activation of the MAPK pathway. As manifested, loss of Bach1 was able to repress p-p38, p-AKT1, c-Fos, c-Jun protein levels in lung CSCs. Inhibition of MAPK signaling remarkably restrained lung CSCs growth and CSCs properties induced by Bach1 overexpression.ConclusionIn summary, we imply that Bach1 demonstrates great potential for the treatment of lung cancer metastasis and recurrence via activating CD44 and MPAK signaling.

Impact of bacterial volatiles on phytopathogenic fungi: an in vitro study on microbial competition and interaction.

Microorganisms in the rhizosphere are abundant and exist in very high taxonomic diversity. The major players are bacteria and fungi, and bacteria have evolved many strategies to prevail over fungi, among them harmful enzyme activities and noxious secondary metabolites. Interactions between plant growth promoting rhizobacteria and phytopathogenic fungi are potentially valuable since the plant would benefit from fungal growth repression. In this respect, the role of volatile bacterial metabolites in fungistasis has been demonstrated, but the mechanisms of action are less understood. We used three phytopathogenic fungal species (Sclerotinia sclerotiorum, Rhizoctonia solani, and Juxtiphoma eupyrena) as well as one non-phytopathogenic species (Neurospora crassa) and the plant growth promoting rhizobacterium Serratia plymuthica 4Rx13 in co-cultivation assays to investigate the influence of bacterial volatile metabolites on fungi on a cellular level. As a response to the treatment, we found elevated lipid peroxidation, which indirectly reflected the loss of fungal cell membrane integrity. An increase in superoxide dismutase, catalase, and laccase activities indicated oxidative stress. Acclimation to these adverse growth conditions completely restored fungal growth. One of the bioactive bacterial volatile compounds seemed to be ammonia, which was a component of the bacterial volatile mixture. Applied as a single compound in biogenic concentrations ammonia also caused an increase in lipid peroxidation and enzyme activities, but the extent and pattern did not fully match the effect of the entire bacterial volatile mixture.

MicroRNA-33b replacement effect on growth and migration inhibition in ovarian cancer cells.

Ovarian cancer is a devastating gynecological disease which is considered the major cause of cancer fatality around the world. The down-regulation of microRNA-33b (miR-33b) was reported in some malignancies. Hence, we transfected the miR-33b mimic into SKOV3 cells and evaluated the impacts of this interference on the growth and migration repression of these tumor cells as well as on targeted genes expression. In our study, transfecting the miR-33b mimic and inhibitor, negative control (NC), and NC inhibitor were established using Lipofectamine 2000. The cytotoxic effects of miR-33b were evaluated by MTT. To assess the miR-33b effects on cell migration, a scratching test was applied. The expression levels of miR-33b, ADAMTS, C-Myc, MMP9, K-Ras, and CXCR4 were evaluated using qRT-PCR. These findings indicate that transfection of miR-143mimic had no marked effects on the SKOV3 cell line. As expected, miR-33b relative expression levels were as follows: miR-33b mimic >NC and NC inhibitor >miR-33b inhibitor (p<0.01). Moreover, transfected miR-33b mimic could suppress SKOV3 cells' proliferation, whereas transfected miR-33b inhibitor could promote cell proliferation (p<0.01). MiR-33b overexpression significantly down-regulated the MMP9, CXCR-4, c-Myc, ADAMTS, and K-Ras mRNA levels (p<0.05). As expected, these results confirm the tumor-suppressive effect of miR-33b in the SKOV3 ovarian cancer cell line by reducing cell survival, proliferation, and migration.

LysR-type transcriptional regulator FinR is required for phenazine and pyrrolnitrin biosynthesis in biocontrol Pseudomonas chlororaphis strain G05.

Phenazine-1-carboxylic acid and pyrrolnitrin, the two secondary metabolites produced by Pseudomonas chlororaphis G05, serve as biocontrol agents that mainly contribute to the growth repression of several fungal phytopathogens. Although some regulators of phenazine-1-carboxylic acid biosynthesis have been identified, the regulatory pathway involving phenazine-1-carboxylic acid synthesis is not fully understood. We isolated a white conjugant G05W03 on X-Gal-containing LB agar during our screening of novel regulator candidates using transposon mutagenesis with a fusion mutant G05Δphz::lacZ as a recipient. By cloning of DNA adjacent to the site of the transposon insertion, we revealed that a LysR-type transcriptional regulator (LTTR) gene, finR, was disrupted in the conjugant G05W03. To confirm the regulatory function of FinR, we constructed the finR-knockout mutant G05ΔfinR, G05Δphz::lacZΔfinR, and G05Δprn::lacZΔfinR, using the wild-type strain G05 and its fusion mutant derivatives as recipient strains, respectively. We found that the expressions of phz and prn operons were dramatically reduced in the finR-deleted mutant. With quantification of the production of antifungal metabolites biosynthesized by the finR-negative strain G05ΔfinR, it was shown that FinR deficiency also led to decreased yield of phenazine-1-carboxylic acid and pyrrolnitrin. In addition, the pathogen inhibition assay confirmed that the production of phenazine-1-carboxylic acid was severely reduced in the absence of FinR. Transcriptional fusions and qRT-PCR verified that FinR could positively govern the transcription of the phz and prn operons. Taken together, FinR is required for antifungal metabolite biosynthesis and crop protection against some fungal pathogens.Key points• A novel regulator FinR was identified by transposon mutagenesis.• FinR regulates antifungal metabolite production.• FinR regulates the phz and prn expression by binding to their promoter regions.

The blue light receptor CRY1 interacts with GID1 and DELLA proteins to repress gibberellin signaling and plant growth

Improvements in plant architecture, such as reduced plant height under high-density planting, are important for agricultural production. Light and gibberellin (GA) are essential external and internal cues that affect plant architecture. In this study, we characterize the direct interaction of distinct receptors that link light and GA signaling in Arabidopsis (Arabidopsis thaliana) and wheat (Triticum aestivum L.). We show that the light receptor CRY1 represses GA signaling through interaction with all five DELLA proteins and promotion of RGA protein accumulation in Arabidopsis. Genetic analysis shows that CRY1-mediated growth repression is achieved by means of the DELLA proteins. Interestingly, we find that CRY1 also directly interacts with the GA receptor GID1 to competitively inhibit the GID1-GAI interaction. We also show that overexpression of TaCRY1a reduces plant height and coleoptile growth in wheat and that TaCRY1a interacts with both TaGID1 and Rht1 to competitively attenuate the TaGID1-Rht1 interaction. Based on these findings, we propose that the photoreceptor CRY1 competitively inhibits the GID1-DELLA interaction, thereby stabilizing DELLA proteins and enhancing their repression of plant growth.

Aberrant nuclear lamina contributes to the malignancy of human gliomas

Glioma is the most common type of tumor in the central nervous system, accounting for around 80% of all malignant brain tumors. Previous studies showed a significant association between nuclear morphology and the malignant progress of gliomas. By virtue of integrated proteomics and genomics analyses as well as experimental validations, we identify three nuclear lamin genes (LMNA, LMNB1, and LMNB2) that are significantly upregulated in glioma tissues compared with normal brain tissues. We show that elevated expressions of LMNB1, LMNB2, and LMNA in glioma cells are highly associated with the rapid progression of the disease and the knockdown of LMNB1, LMNB2, and LMNA dramatically suppresses glioma progression in both in vitro and in vivo mouse models. Moreover, the repression of glioma cell growth by lamin knockdown is mediated by the pRb-mediated G1-S inhibition. On the contrary, overexpression of lamins in normal human astrocytes dramatically induced nuclear morphological aberrations and accelerated cell growth. Together, our multi-omics-based analysis has revealed a previously unrecognized role of lamin genes in gliomagenesis, providing a strong support for the key link between aberrant tumor nuclear shape and the survival of glioma patients. Based on these findings, lamins are proposed to be potential oncogene targets for therapeutic treatments of brain tumors.

Xyloglucan Remodeling Defines Auxin-Dependent Differential Tissue Expansion in Plants.

Size control is a fundamental question in biology, showing incremental complexity in plants, whose cells possess a rigid cell wall. The phytohormone auxin is a vital growth regulator with central importance for differential growth control. Our results indicate that auxin-reliant growth programs affect the molecular complexity of xyloglucans, the major type of cell wall hemicellulose in eudicots. Auxin-dependent induction and repression of growth coincide with reduced and enhanced molecular complexity of xyloglucans, respectively. In agreement with a proposed function in growth control, genetic interference with xyloglucan side decorations distinctly modulates auxin-dependent differential growth rates. Our work proposes that auxin-dependent growth programs have a spatially defined effect on xyloglucan’s molecular structure, which in turn affects cell wall mechanics and specifies differential, gravitropic hypocotyl growth.

L-Ascorbic Acid Shapes Bovine Pasteurella multocida Serogroup A Infection.

Bovine Pasteurella multocida serogroup A (bovine PmA) is one of the most important pathogens causing fatal pneumonia in cattle. However, it is largely unknown how nutrition shapes bovine PmA infection. Here, we discovered that the infected lung held the highest bacterial density than other tissues during infection. By screening the different metabolites between high (lung)- and low (liver)-bacterial density tissues, the present work revealed that L-ascorbic acid and L-aspartic acid directly influenced bovine P. multocida growth. Interestingly, L-ascorbic acid, which is expressed at higher levels in the infected livers, inhibited bovine PmA growth as well as virulence factor expression and promoted macrophage bactericidal activity in vitro. In addition, ascorbic acid synthesis was repressed upon bovine PmA infection, and supplementation with exogenous L-ascorbic acid significantly reduced the bacterial burden of the infected lungs and mouse mortality. Collectively, our study has profiled the metabolite difference of the murine lung and liver during bovine PmA infection. The screened L-ascorbic acid showed repression of bovine PmA growth and virulence expression in vitro and supplementation could significantly increase the survival rate of mice and reduce the bacterial load in vivo, which implied that L-ascorbic acid could serve as a potential protective agent for bovine PmA infection in clinic.

Abstract 2406: The essential role of ATP binding to the mitochondrial protein ATAD3A in driving oncogenesis of head and neck squamous cell carcinoma

Abstract Head and neck squamous cell carcinoma (HNSCC) represents only 4% of all cancers in the US, but the adverse impact of this disease on health quality is dramatic. There has been little improvement in HNSCC treatment outcomes in decades, and a better understanding of the molecular biology of HNSCC is urgently needed to facilitate the design of anti-HNSCC therapies. The mitochondrial ATPase family AAA-domain containing protein 3A (ATAD3A) has been demonstrated as an oncogene in breast and lung cancer. However, nothing has been reported regarding its role in HNSCC. We report here that loss of ATAD3A expression inhibits HNSCC cell growth as evidenced by reduced cell proliferation and decreased the ability of colony formation and anchorage-independent growth in soft agar, whereas gain of ATAD3A expression counteracts the observed effects. Overexpression of a Walker A dead mutant of ATAD3A (ATAD3AK358) leads to a suppression in HNSCC cell growth and lipids synthesis, suggesting a potent dominant-negative effect of defective ATP-binding of ATAD3A. In line with the in vitro data, overexpression of ATAD3A facilities tumor growth in an orthotopic mouse model of HNSCC. In contrast, inhibition of ATAD3A function by knockout of ATAD3A or expression of ATAD3AK358 induces significant repression of tumor growth. These findings indicate that the mitochondrial protein ATAD3A plays an oncogenic role in HNSCC, and abrogating its ATP-binding ability may represent a promising regimen for better treatment of patients with HNSCC. Citation Format: Liwei Lang, Tiffany Lam, Alex Chen, Chole Shay, Yong Teng. The essential role of ATP binding to the mitochondrial protein ATAD3A in driving oncogenesis of head and neck squamous cell carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2406.

Leaf Shape Diversity: From Genetic Modules to Computational Models.

Plant leaves display considerable variation in shape. Here, we introduce key aspects of leaf development, focusing on the morphogenetic basis of leaf shape diversity. We discuss the importance of the genetic control of the amount, duration, and direction of cellular growth for the emergence of leaf form. We highlight how the combined use of live imaging and computational frameworks can help conceptualize how regulated cellular growth is translated into different leaf shapes. In particular, we focus on the morphogenetic differences between simple and complex leaves and how carnivorous plants form three-dimensional insect traps. We discuss how evolution has shaped leaf diversity in the case of complex leaves, by tinkering with organ-wide growth and local growth repression, and in carnivorous plants, by modifying the relative growth of the lower and upper sides of the leaf primordium to create insect-digesting traps.

Uncoupling glucose sensing from GAL metabolism for heterologous lactose fermentation in Saccharomyces cerevisiae.

Development of a system for direct lactose to ethanol fermentation provides a market for the massive amounts of underutilized whey permeate made by the dairy industry. For this system, glucose and galactose metabolism were uncoupled in Saccharomyces cerevisiae by deleting two negative regulatory genes, GAL80 and MIG1, and introducing the essential lactose hydrolase LAC4 and lactose transporter LAC12, from the native but inefficient lactose fermenting yeast Kluyveromyces marxianus. Previously, integration of the LAC4 and LAC12 genes into the MIG1 and NTH1 loci was achieved to construct strain AY-51024M. Low rates of lactose conversion led us to generate the Δmig1Δgal80 diploid mutant strain AY-GM from AY-5, which exhibited loss of diauxic growth and glucose repression, subsequently taking up galactose for consumption at a significantly higher rate and yielding higher ethanol concentrations than strain AY-51024M. Similarly, in cheese whey permeate powder solution (CWPS) during three, repeated, batch processes in a 5L bioreactor containing either 100g/L or 150g/L lactose, the lactose uptake and ethanol productivity rates were both significantly greater than that of AY-51024M, while the overall fermentation times were considerably lower. Using the Cre-loxp system for deletion of the MIG1 and GAL80 genes to relieve glucose repression, and LAC4 and LAC12 overexpression to increase lactose uptake and conversion provides an efficient basis for yeast fermentation of whey permeate by-product into ethanol.

MiR-206-G6PD axis regulates lipogenesis and cell growth in hepatocellular carcinoma cell.

miR-206 plays an essential role in repressing the growth of multiple cancer cells. Glucose-6-phosphate dehydrogenase (G6PD) is the rate-limiting enzyme of the pentose phosphate pathway. However, it is mostly unknown whether G6PD is associated with miR-206-mediated growth repression of hepatocellular carcinoma (HCC) cells. In this study, we found that the expression of G6PD was upregulated in HCC patients and cell lines, whereas the expression of miR-206 was negatively associated with the clinical staging criterion of primary liver cancer. Overexpression of G6PD increased lipid accumulation and promoted cell proliferation. Conversely, inhibition of G6PD expression decreased lipid accumulation and suppressed cell proliferation. Moreover, miR-206 could directly bind to G6PD mRNA 3´-UTR and downregulate G6PD level. Overexpression of G6PD significantly attenuated the miR-206 mimic-mediated suppression of lipid accumulation and cell proliferation. In summary, the results demonstrated that miR-206 could inhibit lipid accumulation and growth of HCC cells by targeting G6PD, suggesting that the miR-206-G6PD axis may be a promising target for treating HCC.

Dual β-Catenin and γ-Catenin Loss in Hepatocytes Impacts Their Polarity through Altered Transforming Growth Factor-β and Hepatocyte Nuclear Factor 4α Signaling

Hepatocytes are highly polarized epithelia. Loss of hepatocyte polarity is associated with various liver diseases, including cholestasis. However, the molecular underpinnings of hepatocyte polarization remain poorly understood. Loss of β-catenin at adherens junctions is compensated by γ-catenin and dual loss of both catenins in double knockouts (DKOs) in mice liver leads to progressive intrahepatic cholestasis. However, the clinical relevance of this observation, and further phenotypic characterization of the phenotype, is important. Herein, simultaneous loss of β-catenin and γ-catenin was identified in a subset of liver samples from patients of progressive familial intrahepatic cholestasis and primary sclerosing cholangitis. Hepatocytes in DKO mice exhibited defects in apical-basolateral localization of polarity proteins, impaired bile canaliculi formation, and loss of microvilli. Loss of polarity in DKO livers manifested as epithelial-mesenchymal transition, increased hepatocyte proliferation, and suppression of hepatocyte differentiation, which was associated with up-regulation of transforming growth factor-β signaling and repression of hepatocyte nuclear factor 4α expression and activity. In conclusion, concomitant loss of the two catenins in the liver may play a pathogenic role in subsets of cholangiopathies. The findings also support a previously unknown role of β-catenin and γ-catenin in the maintenance of hepatocyte polarity. Improved understanding of the regulation of hepatocyte polarization processes by β-catenin and γ-catenin may potentially benefit development of new therapies for cholestasis.

MYB3R-mediated active repression of cell cycle and growth under salt stress in Arabidopsis thaliana.

Under environmental stress, plants are believed to actively repress their growth to save resource and alter its allocation to acquire tolerance against the stress. Although a lot of studies have uncovered precise mechanisms for responding to stress and acquiring tolerance, the mechanisms for regulating growth repression under stress are not as well understood. It is especially unclear which particular genes related to cell cycle control are involved in active growth repression. Here, we showed that decreased growth in plants exposed to moderate salt stress is mediated by MYB3R transcription factors that have been known to positively and negatively regulate the transcription of G2/M-specific genes. Our genome-wide gene expression analysis revealed occurrences of general downregulation of G2/M-specific genes in Arabidopsis under salt stress. Importantly, this downregulation is significantly and universally mitigated by the loss of MYB3R repressors by mutations. Accordingly, the growth performance of Arabidopsis plants under salt stress is significantly recovered in mutants lacking MYB3R repressors. This growth recovery involves improved cell proliferation that is possibly due to prolonging and accelerating cell proliferation, which were partly suggested by enlarged root meristem and increased number of cells positive for CYCB1;1-GUS. Our ploidy analysis further suggested that cell cycle progression at the G2 phase was delayed under salt stress, and this delay was recovered by loss of MYB3R repressors. Under salt stress, the changes in expression of MYB3R activators and repressors at both the mRNA and protein levels were not significant. This observation suggests novel mechanisms underlying MYB3R-mediated growth repression under salt stress that are different from the mechanisms operating under other stress conditions such as DNA damage and high temperature.

Understanding Ethanol Tolerance Mechanism in Saccharomyces cerevisiae to Enhance the Bioethanol Production: Current and Future Prospects

The commercial production of bioethanol from lignocellulosic biomass is challenged by the repression of cell growth and compromised fermentation conditions. However, employing Saccharomyces cerevisiae is an economically feasible process resulting in the effective conversion of fermentable sugars to bioethanol. S. cerevisiae’s high productive feature is contributed by robust alcohol dehydrogenase and the ability to tolerate various stresses during the fermentation process. The present review employs various bioinformatics pipeline to assess the structural insights of ADH and interaction among the tolerance genes. Docking of S. cerevisiae’s ADH interaction shows the high binding affinity of − 2.81 Kcal/mol with acetaldehyde contributed by four zinc fingers. In inhibitor tolerance capacity of S. cerevisiae was explored. The STRING platform sheds light on the mechanism and interaction of ASR1 and other stress-responsive elements playing a pivotal role in ethanol tolerance. The stress-responsive genes such as HSPs and MSN2/4 provide balanced physiology under various stress conditions. The present review unravels the complex mechanism behind the inhibitor and ethanol tolerance, directing to several bottlenecks for the improvisation of S. cerevisiae’s performance.