Measurement of HIV Rev-Rev Response Element Functional Activity.

Retroviruses must overcome cellular restrictions to the nucleocytoplasmic export of viral mRNAs that retain introns in order to complete their replication cycle. HIV accomplishes this using a system comprised of a trans-acting viral protein, Rev, and a cis-acting RNA secondary structure in the viral genome, the Rev-Response Element (RRE). HIV primary isolates differ with respect to the sequence and functional activity of the Rev-RRE system. Here, we describe a high throughput assay system for analyzing Rev-RRE functional activity using packageable viral vectors.

Slide-tags enables single-nucleus barcoding for multimodal spatial genomics.

Recent technological innovations have enabled the high-throughput quantification of gene expression and epigenetic regulation within individual cells, transforming our understanding of how complex tissues are constructed1-6. However, missing from these measurements is the ability to routinely and easily spatially localize these profiled cells. We developed a strategy, Slide-tags, in which single nuclei within an intact tissue section are tagged with spatial barcode oligonucleotides derived from DNA-barcoded beads with known positions. These tagged nuclei can then be used as an input into a wide variety of single-nucleus profiling assays. Application of Slide-tags to the mouse hippocampus positioned nuclei at less than 10 µm spatial resolution and delivered whole-transcriptome data that are indistinguishable in quality from ordinary single-nucleus RNA-sequencing data. To demonstrate that Slide-tags can be applied to a wide variety of human tissues, we performed the assay on brain, tonsil and melanoma. We revealed cell-type-specific spatially varying gene expression across cortical layers and spatially contextualized receptor-ligand interactions driving B cell maturation in lymphoid tissue. A major benefit of Slide-tags is that it is easily adaptable to almost any single-cell measurement technology. As a proof of principle, we performed multiomic measurements of open chromatin, RNA and T cell receptor (TCR) sequences in the same cells from metastatic melanoma, identifying transcription factor motifs driving cancer cell state transitions in spatially distinct microenvironments. Slide-tags offers a universal platform for importing the compendium of established single-cell measurements into the spatial genomics repertoire.

Stuxnet fine-tunes Notch dose during development using a functional Polycomb response element.

Evolutionarily conserved Notch signaling is highly sensitive to changes in Notch receptor dose caused by intrinsic and environmental fluctuations. It is well known that epigenetic regulation responds dynamically to genetic, cellular and environmental stresses. However, it is unclear whether the Notch receptor dose is directly regulated at the epigenetic level. Here, by studying the role of the upstream epigenetic regulator Stuxnet (Stx) in Drosophila developmental signaling, we find that Stx promotes Notch receptor mRNA expression by counteracting the activity of Polycomb repressive complex 1 (PRC1). In addition, we provide evidence that Notch is a direct PRC1 target by identifying and validating in vivo the only bona fide Polycomb response element (PRE) among the seven Polycomb group (PcG)-binding sites revealed by DamID-seq and ChIP-seq analysis. Importantly, in situ deletion of this PRE results in increased Notch expression and phenotypes resembling Notch hyperactivation in cell fate specification. These results not only underscore the importance of epigenetic regulation in fine-tuning the Notch activity dose, but also the need to assess the physiological significance of omics-based PcG binding in development.

Carnitine o-octanoyltransferase is a p53 target that promotes oxidative metabolism and cell survival following nutrient starvation.

Whereas it is known that p53 broadly regulates cell metabolism, the specific activities that mediate this regulation remain partially understood. Here, we identified carnitine o-octanoyltransferase (CROT) as a p53 transactivation target that is upregulated by cellular stresses in a p53-dependent manner. CROT is a peroxisomal enzyme catalyzing very long-chain fatty acids conversion to medium chain fatty acids that can be absorbed by mitochondria during ß-oxidation. p53 induces CROT transcription through binding to consensus response elements in the 5'-UTR of CROT mRNA. Overexpression of WT but not enzymatically inactive mutant CROT promotes mitochondrial oxidative respiration, while downregulation of CROT inhibits mitochondrial oxidative respiration. Nutrient depletion induces p53-dependent CROT expression that facilitates cell growth and survival; in contrast, cells deficient in CROT have blunted cell growth and reduced survival during nutrient depletion. Together, these data are consistent with a model where p53-regulated CROT expression allows cells to be more efficiently utilizing stored very long-chain fatty acids to survive nutrient depletion stresses.

A Multi-Omics Approach Reveals Features That Permit Robust and Widespread Regulation of IFN-Inducible Antiviral Effectors.

The antiviral state, an initial line of defense against viral infection, is established by a set of IFN-stimulated genes (ISGs) encoding antiviral effector proteins. The effector ISGs are transcriptionally regulated by type I IFNs mainly via activation of IFN-stimulated gene factor 3 (ISGF3). In this study, the regulatory elements of effector ISGs were characterized to determine the (epi)genetic features that enable their robust induction by type I IFNs in multiple cell types. We determined the location of regulatory elements, the DNA motifs, the occupancy of ISGF3 subunits (IRF9, STAT1, and STAT2) and other transcription factors, and the chromatin accessibility of 37 effector ISGs in murine dendritic cells. The IFN-stimulated response element (ISRE) and its tripartite version occurred most frequently in the regulatory elements of effector ISGs than in any other tested ISG subsets. Chromatin accessibility at their promoter regions was similar to most other ISGs but higher than at the promoters of inflammation-related cytokines, which were used as a reference gene set. Most effector ISGs (81.1%) had at least one ISGF3 binding region proximal to the transcription start site (TSS), and only a subset of effector ISGs (24.3%) was associated with three or more ISGF3 binding regions. The IRF9 signals were typically higher, and ISRE motifs were "stronger" (more similar to the canonical sequence) in TSS-proximal versus TSS-distal regulatory regions. Moreover, most TSS-proximal regulatory regions were accessible before stimulation in multiple cell types. Our results indicate that "strong" ISRE motifs and universally accessible promoter regions that permit robust, widespread induction are characteristic features of effector ISGs.

WASH regulates the oxidative stress Nrf2/ARE pathway to inhibit proliferation and promote apoptosis of HeLa cells under the action of Jolkinolide B.

Jolkinolide B (JB), a diterpenoid compound isolated from the roots of Euphorbia fischeriana, has gained research attention for its antitumor effects. In recent years, JB reportedly displayed anti-tumor activity in solid tumors, such as breast, ovarian, and prostate cancer, and leukemia. In this study, we evaluated the effect of JB on HeLa cells with a focus on cell growth inhibition and related mechanisms. HeLa cells were cultured in vitro and divided into a blank control group, HeLa-Scramble (0, 0.25, 0.5 mM), and Wiskott-Aldrich syndrome protein and SCAR homolog (WASH) protein silenced group, HeLa-shWASH (0, 0.25, 0.5 mM). Morphological changes were observed using an inverted microscope. The inhibition rate of cell proliferation was detected using the WST-1 method. Flow cytometry Brdu+PI double standard method was used to detect cell replication ability and FITC+PI double standard method was used to detect cell apoptosis rate. Western blot was used to verify the expression of Nrf2, HO-1, WASH, Bax, Bcl-2, and PCNA. The mRNA expression of cytokines (IL-1α, IL-6, and IL-8) was detected using RT-qPCR. The results showed that JB induced cell apoptosis and arrested cells at the G2/M phase in HeLa-shWASH cells compared with HeLa-Scramble cells (P < 0.05, P < 0.01, respectively). In addition, JB upregulated IL-1α, IL-6, and IL-8 in HeLa-shWASH cells. We conclude that WASH protein participates in JB-induced regulation of the Nrf2/ARE pathway, aggravates inflammatory responses, and promotes cancer cell apoptosis, thus inhibiting the proliferation and invasion abilities of HeLa cells. JB may have anti-tumor effects and potential clinical value for the treatment of cervical cancer.

Deciphering the mechanism of p73 recognition of p53 response elements using the crystal structure of p73-DNA complexes and computational studies.

p73 belongs to p53 family transcription factor activating more than 50% of cell fate p53 target genes involved in cell cycle, apoptosis, DNA damage response alongside neuronal system development and differentiation by binding to 20-bp response elements (REs) having sequence motif (PPPC-A/T-T/A-GYYY) where P-purines and Y-pyrimidines with each 10-bp separated by minimum 0 to 13-bp spacer. The promiscuous nature of recognizing both cell fate and development genes and the underlying RE selectivity mechanism by p73 is not well understood. Here, we report the molecular details of p73 recognizing the REs using the crystal structure of p73 DNA binding domain (DBD) in complex with 12 base pair DNA sequence 5'-cAGGCATGCCTg-3' and molecular dynamics simulations with six different p53 natural promoter sequences. Each 20-base pair natural promoter forms a different major/minor groove due to the presence of nucleotides A/T, A/C, G/G, T/T and G/T at positions 3, 8, 13, 18 uniquely recognized by p73 key residues Lys138 and Arg268. The loops L1 and L3 bearing these residues influence inter-and intra-dimer interfaces interactions and hence p73 forms a unique tetramer with each natural promoter sequence. Structural features of the DNA and the spacing between half-sites influence p73 tetramerization and its transactivation function.

Transcriptional Control of Trpm6 by the Nuclear Receptor FXR.

Farnesoid x receptor (FXR) is a nuclear bile acid receptor that belongs to the nuclear receptor superfamily. It plays an essential role in bile acid biosynthesis, lipid and glucose metabolism, liver regeneration, and vertical sleeve gastrectomy. A loss of the FXR gene or dysregulations of FXR-mediated gene expression are associated with the development of progressive familial intrahepatic cholestasis, tumorigenesis, inflammation, and diabetes mellitus. Magnesium ion (Mg2+) is essential for mammalian physiology. Over 600 enzymes are dependent on Mg2+ for their activity. Here, we show that the Trpm6 gene encoding a Mg2+ channel is a direct FXR target gene in the intestinal epithelial cells of mice. FXR expressed in the intestinal epithelial cells is absolutely required for sustaining a basal expression of intestinal Trpm6 that can be robustly induced by the treatment of GW4064, a synthetic FXR agonist. Analysis of FXR ChIP-seq data revealed that intron regions of Trpm6 contain two prominent FXR binding peaks. Among them, the proximal peak from the transcription start site contains a functional inverted repeat 1 (IR1) response element that directly binds to the FXR-RXRα heterodimer. Based on these results, we proposed that an intestinal FXR-TRPM6 axis may link a bile acid signaling to Mg2+ homeostasis.

Curcumin activates G protein-coupled receptor 97 (GPR97) in a manner different from glucocorticoid.

Curcumin is a yellow pigment in turmeric (Curcuma longa) with various physiological effects in the body. To elucidate the molecular mechanisms by which bioactive compounds exert their function, identification of their molecular targets is crucial. In this study, we show that curcumin activates G protein-coupled receptor 97 (GPR97). Curcumin dose-dependently activated serum-response element-, but not serum-response factor-response element-, nuclear factor of activated T-cell-response element-, or cAMP-response element-, mediated transcription in cells overexpressed with GPR97. The structure-activity relationship indicated that (i) the double-bonds of the central 7-carbon chain were essential for activation; (ii) a methoxy group on the aromatic ring was required for maximal activity; (iii) the addition of glucuronic acid moiety or a methoxy group to the aromatic ring, but not the methylation of the aromatic p-hydroxy group, eliminated the activity; (iv) the stability of curcumin would be related to receptor activation. Both mutant GPR97(T250A) lacking the cleavage at GPCR proteolysis site and mutant GPR97(ΔN) lacking the N-terminal extracellular region were activated by curcumin and its related compounds similar to wild-type GPR97. In contrast, the synthetic glucocorticoid beclomethasone dipropionate and l-Phe activated wild-type GPR97 and GPR97(T250A), but not GPR97(ΔN). Moreover, curcumin exerted an additive effect on the activation of wild-type GPR97 with beclomethasone dipropionate, but not with l-Phe. Taken together, these results indicate that curcumin activates GPR97 coupled to Gi/Go subunit, and suggest that curcumin and glucocorticoid activate GPR97 in a different manner.

Structural Characterization of the Interaction of Hypoxia Inducible Factor-1 with Its Hypoxia Responsive Element at the -964G > A Variation Site of the HLA-G Promoter Region.

Human Antigen Leukocyte-G (HLA-G) gene encodes an immune checkpoint molecule that has restricted tissue expression in physiological conditions; however, the gene may be induced in hypoxic conditions by the interaction with the hypoxia inducible factor-1 (HIF1). Hypoxia regulatory elements (HRE) located at the HLA-G promoter region and at exon 2 are the major HIF1 target sites. Since the G allele of the -964G > A transversion induces higher HLA-G expression when compared to the A allele in hypoxic conditions, here we analyzed HIF1-HRE complex interaction at the pair-atom level considering both -964G > A polymorphism alleles. Mouse HIF2 dimer crystal (Protein Data Bank ID: 4ZPK) was used as template to perform homology modelling of human HIF1 quaternary structure using MODELLER v9.14. Two 3D DNA structures were built from 5'GCRTG'3 HRE sequence containing the -964G/A alleles using x3DNA. Protein-DNA docking was performed using the HADDOCK v2.4 server, and non-covalent bonds were computed by DNAproDB server. Molecular dynamic simulation was carried out per 200 ns, using Gromacs v.2019. HIF1 binding in the HRE containing -964G allele results in more hydrogen bonds and van der Waals contact formation than HRE with -964A allele. Protein-DNA complex trajectory analysis revealed that HIF1-HRE-964G complex is more stable. In conclusion, HIF1 binds in a more stable and specific manner at the HRE with G allele.

Comprehensive Analysis of SRO Gene Family in Sesamum indicum (L.) Reveals Its Association with Abiotic Stress Responses.

SIMILAR TO RCD-ONEs (SROs) comprise a small plant-specific gene family which play important roles in regulating numerous growth and developmental processes and responses to environmental stresses. However, knowledge of SROs in sesame (Sesamum indicum L.) is limited. In this study, four SRO genes were identified in the sesame genome. Phylogenetic analysis showed that 64 SROs from 10 plant species were divided into two groups (Group I and II). Transcriptome data revealed different expression patterns of SiSROs over various tissues. Expression analysis showed that Group II SROs, especially SiSRO2b, exhibited a stronger response to various abiotic stresses and phytohormones than those in Group I, implying their crucial roles in response to environmental stimulus and hormone signals. In addition, the co-expression network and protein-protein interaction network indicated that SiSROs are associated with a wide range of stress responses. Moreover, transgenic yeast harboring SiSRO2b showed improved tolerance to salt, osmotic and oxidative stress, indicating SiSRO2b could confer multiple tolerances to transgenic yeast. Taken together, this study not only lays a foundation for further functional dissection of the SiSRO gene family, but also provides valuable gene candidates for genetic improvement of abiotic stress tolerance in sesame.

Phenobarbital Induces SLC13A5 Expression through Activation of PXR but Not CAR in Human Primary Hepatocytes.

Phenobarbital (PB), a widely used antiepileptic drug, is known to upregulate the expression of numerous drug-metabolizing enzymes and transporters in the liver primarily via activation of the constitutive androstane receptor (CAR, NR1I3). The solute carrier family 13 member 5 (SLC13A5), a sodium-coupled citrate transporter, plays an important role in intracellular citrate homeostasis that is associated with a number of metabolic syndromes and neurological disorders. Here, we show that PB markedly elevates the expression of SLC13A5 through a pregnane X receptor (PXR)-dependent but CAR-independent signaling pathway. In human primary hepatocytes, the mRNA and protein expression of SLC13A5 was robustly induced by PB treatment, while genetic knockdown or pharmacological inhibition of PXR significantly attenuated this induction. Utilizing genetically modified HepaRG cells, we found that PB induces SLC13A5 expression in both wild type and CAR-knockout HepaRG cells, whereas such induction was fully abolished in the PXR-knockout HepaRG cells. Mechanistically, we identified and functionally characterized three enhancer modules located upstream from the transcription start site or introns of the SLC13A5 gene that are associated with the regulation of PXR-mediated SLC13A5 induction. Moreover, metformin, a deactivator of PXR, dramatically suppressed PB-mediated induction of hepatic SLC13A5 as well as its activation of the SLC13A5 luciferase reporter activity via PXR. Collectively, these data reveal PB as a potent inducer of SLC13A5 through the activation of PXR but not CAR in human primary hepatocytes.

Transcription from the proximal promoter of ELAC1, a gene for tRNA repair, is upregulated by interferons.

tRNase ZS (ELAC1) and TRNT1 function in tRNA recycling. Recently, we have shown that these genes are upregulated in the cells infected with Theiler's mouse encephalitis virus (TMEV), implying that tRNA recycling functions in response to viral infection. To address the molecular mechanism underlying the ELAC1 upregulation in the cells infected with TMEV, we performed luciferase assays using various plasmid constructs harboring the ELAC1 promoter region. The luciferase expression from a construct containing the full-length ELAC1 promoter was augmented by TMEV, poly IC, IFN-ß, or IFN-γ. We identified four IFN-stimulated responsible elements (ISREs) in the proximal promoter region. The luciferase expression from the constructs that lack all the ISREs was strongly reduced compared with that from the constructs with the four ISREs in the presence of IFN-ß or IFN-γ. The observation that the ISREs from the ELAC1 promoter are essential for the gene upregulation by IFN-ß or IFN-γ suggests that the ELAC1 gene is upregulated by IFNs.

Bisphenol A Analogues Suppress Spheroid Attachment on Human Endometrial Epithelial Cells through Modulation of Steroid Hormone Receptors Signaling Pathway.

Bisphenol A (BPA) is a well-known endocrine disruptor, widely used in various consumer products and ubiquitously found in air, water, food, dust, and sewage leachates. Recently, several countries have restricted the use of BPA and replaced them with bisphenol S (BPS) and bisphenol F (BPF), which have a similar chemical structure to BPA. Compared to BPA, both BPS and BPF have weaker estrogenic effects, but their effects on human reproductive function including endometrial receptivity and embryo implantation still remain largely unknown. We used an in vitro spheroid (blastocyst surrogate) co-culture assay to investigate the effects of BPA, BPS, and BPF on spheroid attachment on human endometrial epithelial cells, and further delineated their role on steroid hormone receptor expression. We also used transcriptomics to investigate the effects of BPA, BPS, and BPF on the transcriptome of human endometrial cells. We found that bisphenol treatment in human endometrial Ishikawa cells altered estrogen receptor alpha (ERα) signaling and upregulated progesterone receptors (PR). Bisphenols suppressed spheroid attachment onto Ishikawa cells, which was reversed by the downregulation of PR through PR siRNA. Overall, we found that bisphenol compounds can affect human endometrial epithelial cell receptivity through the modulation of steroid hormone receptor function leading to impaired embryo implantation.

Ferritin L-subunit gene mutation and hereditary hyperferritinaemia cataract syndrome (HHCS): a case report and literature review.

ABSTRACTObjectives: Hereditary hyperferritinaemia cataract syndrome (HHCS) is an autosomal dominant disease characterized by high serum ferritin levels and juvenile bilateral cataracts. It is often caused by mutations in the iron response element (IRE) of the ferritin L-subunit (FTL) gene. Here, we report a 73-year-old woman who presented to clinic with persistently elevated serum ferritin and family history of juvenile bilateral cataracts in four generations.Methods: Exome sequencing was used to identify the mutation of the FTL gene. Moreover, Sanger sequencing was performed to validate the mutation in the proband. We also reviewed the FLT gene mutations in published HHCS cases to provide experience for accurate diagnosis of similar patients.Results: A heterozygous mutation at position +33 (c.-167C > T, chr19:49468598) of the FTL gene was identified in the patient.Discussion: HHCS should be considered in the differential diagnosis of hyperferritinemia, especially in the presence of normal serum iron concentration and transferrin saturation.Conclusion: For patients with unexplained hyperferritinemia and bilateral cataracts who have experienced early vision loss, the establishment of genetic counseling is essential to diagnose other family members who are at risk in time.Abbreviations: FTL: ferritin L-subunit; HHCS: hereditary hyperferritinaemia cataract syndrome; IDT: integrated DNA technologies; IRE: iron response element; IRP: iron regulatory proteins; MRI: magnetic resonance imaging; SNV: single nucleotide variant; UTR: untranslated region.

Self-guarding of MORC3 enables virulence factor-triggered immunity.

Pathogens use virulence factors to inhibit the immune system1. The guard hypothesis2,3 postulates that hosts monitor (or 'guard') critical innate immune pathways such that their disruption by virulence factors provokes a secondary immune response1. Here we describe a 'self-guarded' immune pathway in human monocytes, in which guarding and guarded functions are combined in one protein. We find that this pathway is triggered by ICP0, a key virulence factor of herpes simplex virus type 1, resulting in robust induction of anti-viral type I interferon (IFN). Notably, induction of IFN by ICP0 is independent of canonical immune pathways and the IRF3 and IRF7 transcription factors. A CRISPR screen identified the ICP0 target MORC34 as an essential negative regulator of IFN. Loss of MORC3 recapitulates the IRF3- and IRF7-independent IFN response induced by ICP0. Mechanistically, ICP0 degrades MORC3, which leads to de-repression of a MORC3-regulated DNA element (MRE) adjacent to the IFNB1 locus. The MRE is required in cis for IFNB1 induction by the MORC3 pathway, but is not required for canonical IFN-inducing pathways. As well as repressing the MRE to regulate IFNB1, MORC3 is also a direct restriction factor of HSV-15. Our results thus suggest a model in which the primary anti-viral function of MORC3 is self-guarded by its secondary IFN-repressing function-thus, a virus that degrades MORC3 to avoid its primary anti-viral function will unleash the secondary anti-viral IFN response.

Foxd4l1.1 Negatively Regulates Chordin Transcription in Neuroectoderm of Xenopus Gastrula.

Inhibition of the bone morphogenetic proteins (BMPs) is the primary step toward neuroectoderm formation in vertebrates. In this process, the Spemann organizer of the dorsal mesoderm plays a decisive role by secreting several extracellular BMP inhibitors such as Chordin (Chrd). Chrd physically interacts with BMP proteins and inhibits BMP signaling, which triggers the expression of neural-specific transcription factors (TFs), including Foxd4l1.1. Thus, Chrd induces in a BMP-inhibited manner and promotes neuroectoderm formation. However, the regulatory feedback mechanism of Foxd4l1.1 on mesodermal genes expression during germ-layer specification has not been fully elucidated. In this study, we investigated the regulatory mechanism of Foxd4l1.1 on chrd (a mesodermal gene). We demonstrate that Foxd4l1.1 inhibits chrd expression during neuroectoderm formation in two ways: First, Foxd4l1.1 directly binds to FRE (Foxd4l1.1 response elements) within the chrd promoter region to inhibit transcription. Second, Foxd4l1.1 physically interacts with Smad2 and Smad3, and this interaction blocks Smad2 and Smad3 binding to activin response elements (AREs) within the chrd promoter. Site-directed mutagenesis of FRE within the chrd(-2250) promoter completely abolished repressor activity of the Foxd4l1.1. RT-PCR and reporter gene assay results indicate that Foxd4l1.1 strongly inhibits mesoderm- and ectoderm-specific marker genes to maintain neural fate. Altogether, these results suggest that Foxd4l1.1 negatively regulates chrd transcription by dual mechanism. Thus, our study demonstrates the existence of precise reciprocal regulation of chrd transcription during neuroectoderm and mesoderm germ-layer specification in Xenopus embryos.

SARS-CoV-2 3C-like protease antagonizes interferon-beta production by facilitating the degradation of IRF3.

The prevalence of SARS-CoV-2 is a great threat to global public health. However, the relationship between the viral pathogen SARS-CoV-2 and host innate immunity has not yet been well studied. The genome of SARS-CoV-2 encodes a viral protease called 3C-like protease. This protease is responsible for cleaving viral polyproteins during replication. In this investigation, 293T cells were transfected with SARS-CoV-2 3CL and then infected with Sendai virus (SeV) to induce the RIG-I like receptor (RLR)-based immune pathway. q-PCR, luciferase reporter assays, and western blotting were used for experimental analyses. We found that SARS-CoV-2 3CL significantly downregulated IFN-ß mRNA levels. Upon SeV infection, SARS-CoV-2 3CL inhibited the nuclear translocation of IRF3 and p65 and promoted the degradation of IRF3. This effect of SARS-CoV-2 3CL on type I IFN in the RLR immune pathway opens up novel ideas for future research on SARS-CoV-2.

Sequence-specific dynamics of DNA response elements and their flanking sites regulate the recognition by AP-1 transcription factors.

Activator proteins 1 (AP-1) comprise one of the largest families of eukaryotic basic leucine zipper transcription factors. Despite advances in the characterization of AP-1 DNA-binding sites, our ability to predict new binding sites and explain how the proteins achieve different gene expression levels remains limited. Here we address the role of sequence-specific DNA flexibility for stability and specific binding of AP-1 factors, using microsecond-long molecular dynamics simulations. As a model system, we employ yeast AP-1 factor Yap1 binding to three different response elements from two genetic environments. Our data show that Yap1 actively exploits the sequence-specific flexibility of DNA within the response element to form stable protein-DNA complexes. The stability also depends on the four to six flanking nucleotides, adjacent to the response elements. The flanking sequences modulate the conformational adaptability of the response element, making it more shape-efficient to form specific contacts with the protein. Bioinformatics analysis of differential expression of the studied genes supports our conclusions: the stability of Yap1-DNA complexes, modulated by the flanking environment, influences the gene expression levels. Our results provide new insights into mechanisms of protein-DNA recognition and the biological regulation of gene expression levels in eukaryotes.

Mechanisms Mediating the Regulation of Peroxisomal Fatty Acid Beta-Oxidation by PPARα.

In mammalian cells, two cellular organelles, mitochondria and peroxisomes, share the ability to degrade fatty acid chains. Although each organelle harbors its own fatty acid ß-oxidation pathway, a distinct mitochondrial system feeds the oxidative phosphorylation pathway for ATP synthesis. At the same time, the peroxisomal ß-oxidation pathway participates in cellular thermogenesis. A scientific milestone in 1965 helped discover the hepatomegaly effect in rat liver by clofibrate, subsequently identified as a peroxisome proliferator in rodents and an activator of the peroxisomal fatty acid ß-oxidation pathway. These peroxisome proliferators were later identified as activating ligands of Peroxisome Proliferator-Activated Receptor α (PPARα), cloned in 1990. The ligand-activated heterodimer PPARα/RXRα recognizes a DNA sequence, called PPRE (Peroxisome Proliferator Response Element), corresponding to two half-consensus hexanucleotide motifs, AGGTCA, separated by one nucleotide. Accordingly, the assembled complex containing PPRE/PPARα/RXRα/ligands/Coregulators controls the expression of the genes involved in liver peroxisomal fatty acid ß-oxidation. This review mobilizes a considerable number of findings that discuss miscellaneous axes, covering the detailed expression pattern of PPARα in species and tissues, the lessons from several PPARα KO mouse models and the modulation of PPARα function by dietary micronutrients.