Diverse roles of SARS-CoV-2 Spike and Nucleocapsid proteins in EndMT stimulation through the TGF-ß-MRTF axis inhibited by aspirin.

BACKGROUND: The SARS-CoV-2 virus causes severe COVID-19 in one-fifth of patients. In addition to high mortality, infection may induce respiratory failure and cardiovascular complications associated with inflammation. Acute or prolonged inflammation results in organ fibrosis, the cause of which might be endothelial disorders arising during the endothelial-mesenchymal transition (EndMT). METHODS: HUVECs and HMEC-1 cells were stimulated with SARS-CoV-2 S (Spike) and N (Nucleocapsid) proteins, and EndMT induction was evaluated by studying specific protein markers via Western blotting. Wound healing and tube formation assays were employed to assess the potential of SARS-CoV-2 to stimulate changes in cell behaviour. MRTF nuclear translocation, ROS generation, TLR4 inhibitors, TGF-ß-neutralizing antibodies, and inhibitors of the TGF-ß-dependent pathway were used to investigate the role of the TGF-ß-MRTF signalling axis in SARS-CoV-2-dependent EndMT stimulation. RESULTS: Both viral proteins stimulate myofibroblast trans-differentiation. However, the N protein is more effective at EndMT induction. The TGF-ß-MRTF pathway plays a critical role in this process. The N protein preferentially favours action through TGF-ß2, whose secretion is induced through TLR4-ROS action. TGF-ß2 stimulates MRTF-A and MRTF-B nuclear translocation and strongly regulates EndMT. In contrast, the Spike protein stimulates TGF-ß1 secretion as a result of ACE2 downregulation. TGF-ß1 induces only MRTF-B, which, in turn, weakly regulates EndMT. Furthermore, aspirin, a common nonsteroidal anti-inflammatory drug, might prevent and reverse SARS-CoV-2-dependent EndMT induction through TGF-ß-MRTF pathway deregulation. CONCLUSION: The reported study revealed that SARS-CoV-2 infection induces EndMT. Moreover, it was demonstrated for the first time at the molecular level that the intensity of the EndMT triggered by SARS-CoV-2 infection may vary and depend on the viral protein involved. The N protein acts through TLR4-ROS-TGF-ß2-MRTF-A/B, whereas the S protein acts through ACE2-TGF-ß1-MRTF-B. Furthermore, we identified aspirin as a potential anti-fibrotic drug for treating patients with SARS-CoV-2 infection.

Evening Primrose Extract Modulates TYMS Expression via SP1 Transcription Factor in Malignant Pleural Mesothelioma.

PURPOSE: To determine the mechanism of EPE in downregulating TYMS in MPM cancer. METHODS: The TYMS mRNA expression with epithelial-to-mesenchymal transition biomarkers and nuclear factor SP1 was assessed using the GEO database in a data set of MPM patients (GSE51024). Invasive MPM cell lines were in vitro models for the investigation of TYMS expression after EPE treatment. The tyms promoter SP1 binding sequences were determined using Genomatix v 3.4 software Electrophoretic mobility shift and dual-luciferase reporter assays revealed specific SP1 motifs in the interaction of EPE and reference compounds. Chromatin immunoprecipitation and Re-ChIP were used for the co-occupancy study. RESULTS: In MPM patients, a positive correlation of overexpressed TYMS with mesenchymal TWIST1, FN1 and N-cadherin was observed. EPE and its major components, gallic and ellagic acid (GA and EA, respectively), downregulated TYMS in invasive MPM cells by interacting with particular SP1 motifs on the tyms promoter. The luciferase constructs confirmed the occupation of two SP1 regulatory regions critical for the promotion of TYMS expression. Both EPE and reference standards influenced SP1 translocation into the nucleus. CONCLUSION: EPE components reduced TYMS expression by occupation of SP1 motifs on the tyms promoter and reversed the EMT phenotype of invasive MPM cells. Further in-depth analysis of the molecular docking of polyphenol compounds with SP1 regulatory motifs is required.

Impact of Polyphenols on Inflammatory and Oxidative Stress Factors in Diabetes Mellitus: Nutritional Antioxidants and Their Application in Improving Antidiabetic Therapy.

Diabetes mellitus is a chronic metabolic disorder characterized by hyperglycaemia and oxidative stress. Oxidative stress plays a crucial role in the development and progression of diabetes and its complications. Nutritional antioxidants derived from dietary sources have gained significant attention due to their potential to improve antidiabetic therapy. This review will delve into the world of polyphenols, investigating their origins in plants, metabolism in the human body, and relevance to the antioxidant mechanism in the context of improving antidiabetic therapy by attenuating oxidative stress, improving insulin sensitivity, and preserving ß-cell function. The potential mechanisms of, clinical evidence for, and future perspectives on nutritional antioxidants as adjuvant therapy in diabetes management are discussed.

SARS-CoV-2 S and N protein peptides drive invasion abilities of colon cancer cells through TGF-ß1 regulation.

The COVID-19 pandemic led to the delay of colorectal cancer (CRC) diagnosis, which causes CRC to be treated at more advanced, often metastatic stages. Unfortunately, there is no effective treatment for metastatic CRC stages, which are considered the leading cause of patients' death. The mortality induced by SARS-CoV-2 is significantly higher in cancer patients than in patients with other diseases. Interestingly, COVID-19 patients often develop fibrosis which depends on epithelial-mesenchymal transition (EMT) - the process also involved in cancer progression. The study aimed to verify whether SARS-CoV-2 induces EMT and consequently increases the invasion potential of colon cancer cells. CRC cells were stimulated with SARS-CoV-2 S and N protein peptides and epithelial and mesenchymal markers were analysed with Western blotting to detect the occurrence of the EMT. The migration, invasion assays and MMP-7 secretion were employed to evaluate the potential of SARS-CoV-2 to stimulate the cells invasion in vitro. ELISA assay, TGF-ß1 neutralizing antibodies, TGF-ßR silencing and inhibitors were used to investigate the role of the TGF-ß1 signalling pathways in the SARS-CoV-2-dependent CRC stimulation. The SARS-CoV-2 induced EMT, which increased the invasion ability of CRC cells. Moreover, the SARS-CoV-2 proteins drive colon cancer cell invasion through TGF-ß1. Additionally, secreted TGF-ß1 induced a bystander effect in colon cancer cells. However, blocking TGF-ß1/Smad- and -non-Smad-dependent pathways suppressed the SARS-CoV-2-induced invasiveness of CRC. In conclusion, we revealed that SARS-CoV-2 stimulates the invasion abilities of CRC by regulating TGF-ß1-induced EMT. Our results provide a theoretical basis for using anti-TGF-ß1 therapy to reduce the risk of CRC metastasis during SARS-CoV-2 infection.

Evening primrose seed extract rich in polyphenols modulates the invasiveness of colon cancer cells by regulating the TYMS expression.

Natural polyphenols are plant metabolites exhibiting a broad range of biological activities. Among them, anticancer properties seem to be very desirable. This study examined the anticancer and anti-metastatic properties of the polyphenol-rich extract from the evening primrose seeds (EPE). In vitro and in vivo studies performed in colorectal cancer (CRC) cell lines and AOM-DSS-induced colitis-associated colon cancer in mice revealed the EPE anticancer properties. Furthermore, we studied the EPE activity on metastatic abilities and showed that the EPE inhibited invasiveness in the following models (cells isolated from patients with different invasive stages and cells with induced invasion by either Snail overexpression or CAF stimulation). More importantly, we also demonstrated that the EPE decreases the cell invasiveness of 5-fluorouracil (5-FU) resistant CRC cells. The inhibition of metastasis correlated with a decrease in thymidylate synthetase (TYMS), which has recently been associated with metastatic phenotype development. Our results indicate that the EPE might be an effective anticancer agent in suppressing colon cancer metastasis regardless of the invasiveness cause. Based on these findings, we concluded that the used EPE extract rich in polyphenols inhibits cell invasion by TYMS downregulation.

Thymidylate Synthase Overexpression Drives the Invasive Phenotype in Colon Cancer Cells.

Thymidylate synthase (TYMS) is the crucial enzymatic precursor for DNA biosynthesis and, therefore, the critical target for numerous types of chemotherapy, including the most frequently applied agent in colon cancer treatment 5-fluorouracil (5-FU). TYMS also seems to be associated with cancer metastasis and acquiring mesenchymal character by tumor cells during epithelial-mesenchymal transition (EMT). Based on that knowledge, we decided to investigate the role of TYMS in the modulation of invasive ability in colon cancer cells, where its effect on cancer metastasis has not been studied in detail before. We employed colon cancer cells isolated from different stages of tumor development, cells undergoing EMT, and TYMS overexpressing cells. The elongation ratio, cell migration, invasion assay, and MMP-7 secretion were applied to analyze the cell behavior. Important epithelial and mesenchymal markers characteristic of EMT were examined at the protein level by Western blot assay. Overall, our study showed a correlation between TYMS level and invasion ability in colon cancer cells and, above all, a crucial role of TYMS in the EMT regulation. We postulate that chemotherapeutics that decrease or inhibit TYMS expression could increase the effectiveness of the therapy in patients with colon cancer, especially in the metastatic stage.

Targeted and untargeted metabolomic approach for GDM diagnosis.

Gestational diabetes mellitus (GDM) is a disorder which manifests itself for the first time during pregnancy and is mainly connected with glucose metabolism. It is also known that fatty acid profile changes in erythrocyte membranes and plasma could be associated with obesity and insulin resistance. These factors can lead to the development of diabetes. In the reported study, we applied the untargeted analysis of plasma in GDM against standard glucose-tolerant (NGT) women to identify the differences in metabolomic profiles between those groups. We found higher levels of 2-hydroxybutyric and 3-hydroxybutyric acids. Both secondary metabolites are associated with impaired glucose metabolism. However, they are products of different metabolic pathways. Additionally, we applied lipidomic profiling using gas chromatography to examine the fatty acid composition of cholesteryl esters in the plasma of GDM patients. Among the 14 measured fatty acids characterizing the representative plasma lipidomic cluster, myristic, oleic, arachidonic, and α-linoleic acids revealed statistically significant changes. Concentrations of both myristic acid, one of the saturated fatty acids (SFAs), and oleic acid, which belong to monounsaturated fatty acids (MUFAs), tend to decrease in GDM patients. In the case of polyunsaturated fatty acids (PUFAs), some of them tend to increase (e.g., arachidonic), and some of them tend to decrease (e.g., α-linolenic). Based on our results, we postulate the importance of hydroxybutyric acid derivatives, cholesteryl ester composition, and the oleic acid diminution in the pathophysiology of GDM. There are some evidence suggests that the oleic acid can have the protective role in diabetes onset. However, metabolic alterations that lead to the onset of GDM are complex; therefore, further studies are needed to confirm our observations.

Phytochemicals in Malignant Pleural Mesothelioma Treatment-Review on the Current Trends of Therapies.

Malignant pleural mesothelioma (MPM) is a rare but highly aggressive tumor of pleura arising in response to asbestos fibers exposure. MPM is frequently diagnosed in the advanced stage of the disease and causes poor prognostic outcomes. From the clinical perspective, MPM is resistant to conventional treatment, thus challenging the therapeutic options. There is still demand for improvement and sensitization of MPM cells to therapy in light of intensive clinical studies on chemotherapeutic drugs, including immuno-modulatory and targeted therapies. One way is looking for natural sources, whole plants, and extracts whose ingredients, especially polyphenols, have potential anticancer properties. This comprehensive review summarizes the current studies on natural compounds and plant extracts in developing new treatment strategies for MPM.

Polyphenol Extract from Evening Primrose (Oenothera paradoxa) Inhibits Invasion Properties of Human Malignant Pleural Mesothelioma Cells.

Extracts from the defatted evening primrose (Oenothera paradoxa Hudziok) seeds are the source of a range of stable polyphenolic compounds, including ellagic acid, gallic acid, and catechin. Our studies evaluate, for the first time, the influence of evening primrose isopropanol extract (EPE) on malignant pleural mesothelioma (MPM) cells. MPM is rarely diagnosed, its high aggressiveness and frequently noted chemoresistance limit its treatment schemes and it is characterized by low prognostic features. Here, we demonstrate that EPE inhibited MPM growth in a dose-dependent manner in cells with increased invasion properties. Moreover, EPE treatment resulted in cell cycle arrest in the G2/M phase and increased apoptosis in invasive MPM cell lines. Additionally, EPE strongly limited invasion and MMP-7 secretion in MPM cancer cells. Our original data provide evidence about the potential anti-invasive effects of EPE in MPM therapy treatment.

Associations of Arginine with Gestational Diabetes Mellitus in a Follow-Up Study.

In the reported study we applied the targeted metabolomic profiling employing high pressure liquid chromatography coupled with triple quadrupole tandem mass spectrometry (HPLC-MS/MS) to understand the pathophysiology of gestational diabetes mellitus (GDM), early identification of women who are at risk of developing GDM, and the differences in recovery postpartum between these women and normoglycemic women. We profiled the peripheral blood from patients during the second trimester of pregnancy and three months, and one year postpartum. In the GDM group Arg, Gln, His, Met, Phe and Ser were downregulated with statistical significance in comparison to normoglycemic (NGT) women. From the analysis of the association of all amino acid profiles of GDM and NGT women, several statistical models predicting diabetic status were formulated and compared with the literature, with the arginine-based model as the most promising of the screened ones (area under the curve (AUC) = 0.749). Our research results have shed light on the critical role of arginine in the development of GDM and may help in precisely distinguishing between GDM and NGT and earlier detection of GDM but also in predicting women with the increased type 2 diabetes mellitus (T2DM) risk.

Metabolomic Insight into Lipid and Protein Profile in Diabetes Using Mass Spectrometry.

In recent years, metabolomics has become a necessary tool for understanding the impact of external and pathological factors on the operation of biological systems. The first reports of metabolomics date back to the 1970s, however, the area only began to develop dynamically at the beginning of this century and has proved effective only during the present decade. The five primary tools used in this form of analysis are NMR spectrometry, HPLC, TLC-UV, GC-MS and LC-MS/MS, with MS as the most universal approach, particularly when used together with chromatographic separation and NMR. Diabetes mellitus type 2 (T2DM) is a rapidly growing problem with global consequences. The metabolomic approach has been extensively applied to examining T2DM, insulin resistance and obesity, not only to assess the development of the disease, but also to discover its potential biomarkers. The presented review summarizes current studies on lipidomic and proteomic profiles in the context of different types of diabetes mellitus disease (T1DM, T2DM and GDM), as determined by chromatography-coupled mass spectrometry.

Continuous Glucose Monitoring in Type 1 Diabetes Pregnancy Shows that Fetal Heart Rate Correlates with Maternal Glycemia.

BACKGROUND: Much evidence has shown that pregnancies in women with preexisting diabetes are affected by an increased risk of maternal and fetal adverse outcomes, probably linked to poor glycemic control. Despite great progress in medical care, the rate of stillbirths remains much higher in diabetes patients than in the general population. Recent technological advances in the field of glucose monitoring and noninvasive fetal heart rate monitoring made it possible to observe the fetal-maternal dependencies in a continuous manner. SUBJECTS AND METHODS: Fourteen type 1 diabetes patients were involved into the study and fitted with a blinded continuous glucose monitoring (CGM) recorder. Fetal electrocardiogram data were recorded using the Monica AN24™ device (Monica Healthcare Ltd., Nottingham, United Kingdom), the recordings of which were matched with CGM data. Statistical analysis was performed using a generalized mixed-effect logistic regression to account for individual factors. RESULTS: The mean number of paired data points per patient was 254±106, representing an observation period of 21.2±8.8 h. Mean glycemia equaled 5.64±0.68 mmol/L, and mean fetal heart rate was 135±6 beats/min. Higher glycemia correlated with fetal heart rate (R=0.32; P<0.0001) and was associated with higher odds of the fetus developing small accelerations (odds ratio=1.05; 95% confidence interval, 1.00-1.10; P=0.04). CONCLUSIONS: Elevated maternal glycemia of mothers with diabetes is associated with accelerations of fetal heart rate.

The association of leukocyte phosphatidylinositol 3-kinase delta overexpression with gestational diabetes mellitus (GDM).

INTRODUCTION: An increasing body of evidence has linked diabetes to inflammation. The phosphatidylinositol 3-kinase delta (PI3-K delta), a member of the PI3K class IA family, has been implicated in the regulation of inflammation since it is predominantly expressed in leukocytes. To date, no information has been available on the relationship of leukocyte PI3-K delta with gestational diabetes mellitus (GDM). Therefore, the aim of this study was to investigate changes in leukocyte PIK3CD mRNA expression in GDM women and, in turn, to correlate them with anthropometric and metabolic parameters of patients. Additionally, an association between leukocyte mRNA expression of PIK3CD and Sirtuin 1 (SIRT1) was determined. MATERIAL AND METHODS: Blood samples from women with normal glucose tolerance (NGT; n = 43) and GDM (n = 132) at 24-33 weeks of gestation were collected. After isolating leukocytes from the blood, quantitative real time PCR (qRT-PCR) was performed to determine PIK3CD gene expression in these cells. Univariate regression analyses were used to assess an association of leukocyte PIK3CD mRNA level with clinical characteristics of patients as well as with leukocyte SIRT1 mRNA expression. RESULTS: Leukocyte PIK3CD mRNA was increased by 1.98-fold in the GDM v. NGT subjects and inversely correlated with low-density lipoprotein cholesterol (LDL-C) and total cholesterol (TC) in diabetic pregnancy. There were also significant positive correlations of leukocyte PIK3CD mRNA with plasma glucose concentration at 2h of 75 g oral glucose tolerance test (OGTT) and SIRT1 mRNA in the whole study population (both P < 0.05). CONCLUSIONS: GDM is accompanied by leukocyte PIK3CD overexpression associated with reduced plasma LDL-C and TC levels, as well as with hyperglycaemia and elevated leukocyte SIRT1 mRNA.

The elevated gene expression level of the A(2B) adenosine receptor is associated with hyperglycemia in women with gestational diabetes mellitus.

BACKGROUND: Adenosine receptors denoted by A1 , A2A , A2B , and A3 and encoded by ADORA1, ADORA2A, ADORA2B, and ADORA3 genes, respectively, are adenosine-activated G-protein-coupled receptors that play an important role in obesity and type 2 diabetes mellitus. However, little is known about their significance in gestational diabetes mellitus (GDM). The purpose of this study was to investigate whether there are changes in leukocyte AR expression in GDM patients and whether these alterations are linked to well-known diabetic genes. METHODS: Leukocytes were isolated from the blood of normal glucose tolerant (NGT; n = 35) and GDM (n = 82) pregnant women, and expression of ARs was determined by a semi-quantitative polymerase chain reaction (PCR). Univariate correlation analysis was performed to investigate associations between expression of ARs and anthropometric and metabolic parameters of patients. Furthermore, the identification of diabetic genes linked to significantly differentiated leukocyte adenosine receptors expression in GDM women was also carried out with the use of the human diabetes RT(2) profiler PCR arrays. RESULTS: ADORA2B mRNA expression was significantly higher in GDM versus NGT pregnant women (p < 0.05), and positively correlated with the glucose level at 1-h 75-g oral glucose tolerance test (OGTT; r = 0.21, p = 0.044). Nineteen diabetic genes linked to leukocyte ADORA2B overexpression associated with hyperglycemia in GDM women were also identified. CONCLUSIONS: Maternal leukocyte ADORA2B overexpression is associated with hyperglycemia in GDM subjects, and it is accompanied by complex alterations in the expression of diabetes-related genes involved in insulin action, carbohydrate and lipid metabolism, oxidative stress, and inflammation.

[The role of peroxisome proliferator-activated receptors γ (PPARγ) in obesity and insulin resistance]. / Rola receptorów aktywowanych przez proliferatory peroksysomów γ (PPARγ) w otylosci i insulinoopornosci.

Obesity, defined as abnormal or excessive fat accumulation, is currently believed to be a major public health problem worldwide. Over the past 20 years, the prevalence of obesity has increased rapidly in both industrialized and developing countries, resulting in a considerably increased risk of type 2 diabetes mellitus (T2DM) and metabolic syndrome. Although the exact pathophysiological mechanisms underlying these diseases remain unclear, clinical and epidemiological studies support the existence of a relationship between obesity-induced inflammation and insulin resistance linked with the development and progression of metabolic diseases. Adipokines, produced and released by adipose tissue, are considered as factors linking obesity-induced inflammation with insulin resistance, and their regulation through peroxisome proliferator-activated receptors γ (PPARγ also known as NR1C3) is essential in these processes. PPARγ are transcriptional factors belonging to the ligand-activated nuclear receptor superfamily which directly regulate the expression of a large number of genes involved in adipocyte differentiation, lipid and carbohydrate metabolism as well as adipokine synthesis; thereby they are implicated in various metabolic disorders, including obesity, insulin resistance, dyslipidemia, and hypertension. This review summarizes the current literature on a functional relationship of PPARγ with obesity and insulin resistance and, moreover, highlights the significance of synthetic ligands of these receptors in the mentioned metabolic disorders.

New insight into A1 adenosine receptors in diabetes treatment.

The A1 adenosine receptors (A1AR), belonging to the rhodopsin-like superfamily of the G-protein-coupled receptors (GPCRs), may regulate many various cellular processes in cardiovascular, renal, and central nervous systems. In addition, since A(1)AR possesses antilipolytic properties, numerous A1AR agonists and antagonists have been developed, but only some of them with the most promising selective properties in vitro have been advanced to animal studies and clinical trials. In this review, we have summarized the studies on the utility of A1AR selective agonists and antagonists in the regulation of lipid and carbohydrate metabolism and their potential therapeutic applications in diabetes.

Structure and physiological functions of the human peroxisome proliferator-activated receptor gamma.

The peroxisome proliferator-activated receptors (PPARs) belong to the nuclear hormone receptor superfamily. To date, three different PPAR isotypes, namely PPAR-alpha, -delta, and -gamma, have been identified in vertebrates and have distinct patterns of tissue distribution. Like all nuclear receptors, the human PPAR-gamma (hPPAR-gamma) is characterized by a modular structure composed of an N-terminal A/B domain, a DNA-binding domain with two zinc fingers (C domain), a D domain, and a C-terminal ligand-binding domain (E/F domain). Human PPAR-gamma exists in two protein isoforms, hPPAR-gamma(1) and -gamma(2), with different lengths of the N-terminal. The hPPAR-gamma(2) isoform is predominantly expressed in adipose tissue, whereas hPPAR-gamma(1) is relatively widely expressed. Human PPAR-gamma plays a critical physiological role as a central transcriptional regulator of both adipogenic and lipogenic programs. Its transcriptional activity is induced by the binding of endogenous and synthetic lipophilic ligands, which has led to the determination of many roles for PPAR-gamma in pathological states such as type 2 diabetes, atherosclerosis, inflammation, and cancer. Of the synthetic ligands, the thiazolidinedione class of insulin-sensitizing drugs (ciglitazone, pioglitazone, troglitazone, rosiglitazone) is employed clinically in patients with type 2 diabetes.

Chemoselective activation of nucleoside 3'-O-methylphosphonothioates with 1,3,5-triazinyl morpholinium salts.

Chemoselective and stereospecific O-activation of 2'-deoxynucleoside 3'-O-methylphosphonothioates 5 with N-methyl-N-4,6-dimethoxy-1,3,5-triazin-2-yl morpholinium salts results in formation with retention of configuration of 5'-O-DMT-2'-deoxynucleoside 3'-O-(4,6 dimethoxy-1,3,5-triazin-2-yl methylphosphonothioates (7). Active esters 7 are convenient intermediates for hydrolytic interconversion of RP-5 into SP-5 and can be used as monomers for stereoselective synthesis of dinucleoside (3',5')-methyl phosphonothioates.

[DNA structure from A to Z--biological implications of structural diversity of DNA]. / Struktura DNA od A do Z - biologiczne implikacje róznorodnosci strukturalnej DNA.

Deoxyribonucleic acid (DNA) is a biopolymer of nucleotides, usually adopting a double-stranded helical form in cells, with complementary base pairing holding the two strands together. The most stable is B-DNA conformation, although numerous other double helical structures can occur under specific conditions (A-DNA, Z-DNA, P-DNA). The existence of multiple-stranded (triplex, tetraplex) forms in vivo and their biological function in cells are subject of intensive studies.

Mechanisms of coupling between DNA recognition specificity and catalysis in EcoRI endonuclease.

Proteins that bind to specific sites on DNA often do so in order to carry out catalysis or specific protein-protein interaction while bound to the recognition site. Functional specificity is enhanced if this second function is coupled to correct DNA site recognition. To analyze the structural and energetic basis of coupling between recognition and catalysis in EcoRI endonuclease, we have studied stereospecific phosphorothioate (PS) or methylphosphonate (PMe) substitutions at the scissile phosphate GpAATTC or at the adjacent phosphate GApATTC in combination with molecular-dynamics simulations of the catalytic center with bound Mg2+. The results show the roles in catalysis of individual phosphoryl oxygens and of DNA distortion and suggest that a "crosstalk ring" in the complex couples recognition to catalysis and couples the two catalytic sites to each other.