Mirjana Macvanin
@bg.ac.rs
Department for Molecular Genetics and Radiobiology
Vinca Institute for Nuclear Sciences
EDUCATION
Uppsala University, Sweden: PhD in Microbiology (2003)
Belgrade University, Serbia: BSc in Biochemistry (1996)
Scopus Publications
Scholar Citations
Scholar h-index
Scholar i10-index
Scopus Publications
Aleksandra Z Tomic, Sonja S Zafirovic, Zoran M Gluvic, Vladimir S Samardzic, Mirjana T Macvanin, Maja LJ Radunovic, and Esma R Isenovic
SAGE Publications
Background: Subacute thyroiditis (SAT) is an organ-specific disease that various drugs, including COVID-19 vaccines, can trigger. COVID-19 infection has been associated with thyroid gland damage and disease SARS-CoV-2 direct action, euthyroid sick syndrome, and immune-mediated mechanisms are all potential mechanisms of thyroid damage. It denotes thyroid gland inflammation, most commonly of viral origin, and belongs to the transitory, self-limiting thyroid gland diseases group, causing complications in approximately 15% of patients in the form of permanent hypothyroidism. Some authors say SAT is the most common thyroid disease associated with COVID-19. Purpose: The occurrence of SAT many weeks after administering the second COVID-19 vaccine is rare and has limited documentation in academic literature. This study aims to present the occurrence of SAT after administering the COVID-19 vaccine. We present the case of a 37-year-old man who developed SAT 23 days after receiving the second dose of Pfizer BioNTech's COVID-19 mRNA vaccine. Research design and study sample: Due to neck pain and an elevated body temperature (up to 38.2°C), a 37-year-old male subject presented for examination 23 days after receiving the second Pfizer BioNTech mRNA vaccine against SARS-CoV-2 viral infection. The patient denied ever having an autoimmune disease or any other disease. Painful neck palpation and a firm, slightly enlarged thyroid gland with no surrounding lymphadenopathy were identified during the exam. The heart rate was 104 beats per minute. All of the remaining physical findings were normal. Data collection and/or Analysis: Data collected during the disease are integral to the medical record. Results: Hematology and biochemistry analyses at the initial and follow-up visits revealed minor leukocytosis, normocytic anaemia, and thrombocytosis, followed by a mild increase in lactate dehydrogenase and decreased iron levels. The patient's thyroid function and morphology had recovered entirely from post-vaccine SAT. Conclusions: Results from this study emphasise the need for healthcare professionals to promptly report any case of SAT related to COVID-19 vaccination. Further investigation is warranted to understand the immunopathogenesis of COVID-19-associated thyroiditis and the impact of COVID-19 immunization on this condition.
Mirjana T. Macvanin and Esma R. Isenovic
Ovid Technologies (Wolters Kluwer Health)
Diabetes mellitus (DM) refers to a complex cluster of metabolic disorders characterized by hyperglycemia caused by inadequate insulin secretion, insulin resistance, or excessive glucagon secretion. If not correctly treated, the prolonged effects of DM-associated metabolic perturbations lead to systemic vascular complications and cardiovascular disease (CVD), the principal cause of mortality among patients with DM. Given the increase in the global prevalence of diabetes, novel diagnostic and therapeutic procedures are necessary for its effective identification and treatment. Recent findings point to an important role of microRNA (miRNAs) in DM initiation and progression, as well as the occurrence of associated cardiovascular complications. miRNAs are short, highly conserved, single-stranded, non-coding RNAs that contribute to the maintenance of physiological homeostasis through the regulation of crucial processes such as metabolism, cell proliferation, and apoptosis. The increased availability of high-throughput methodologies for identifying and characterizing non-coding RNAs has led to considerable interest in miRNAs as potential biomarkers and therapeutic agents for DM. In this review, we first comprehensively detail the regulatory miRNAs involved in the pathophysiology of DM and diabetic cardiomyopathy (DCMP). Subsequently, we summarize findings regarding the utility of several of these miRNAs as potential prognostic and diagnostic biomarkers for DM and DM-associated CVD. Finally, we evaluate the potential of miRNA-based therapeutic approaches for treating DM and DCMP in the clinical setting.
M. Lačković, Mirjana Macvanin, M. Obradović, Z. Gluvić, E. Sudar-Milovanovic, S. S. Sipetic Grujicic and E. Isenovic
OBJECTIVE
Type 2 diabetes mellitus (T2DM) is a chronic disease with numerous complications that increase mortality and reduce the quality of life (QoL). The current study compares QoL in T2DM patients treated with insulin to those treated with oral antihyperglycemics (OAHs), as well as the frequency and severity of depression in patients.
SUBJECTS AND METHODS
This prospective cross-sectional study included 200 patients with insulin or OAHs. Triglycerides, total cholesterol, low-density lipoprotein, and high-density lipoprotein cholesterol levels were measured. The Beck Depression Inventory and the SF-36 Quality of Life Questionnaire were used to assess depression symptoms and QoL in response to different treatment modalities.
RESULTS
Insulin-treated patients have a longer duration of illness, higher preprandial glycemic levels, lower scores in three of four dimensions of the SF-36 physical component, and a lower score in the SF-36 psychological component's emotional role dimension. Patients on insulin have milder depression symptoms than those with OAHs. Depression symptoms, according to the findings, worsen QoL and glycemic control in insulin-treated patients.
CONCLUSIONS
According to these findings, any treatment modality's success in T2DM patients primarily depends on psychological support and preventive measures that promote and maintain mental health.
Mirjana Macvanin, Zoran Gluvic, Jelena Radovanovic, Magbubah Essack, Xin Gao, and Esma R. Isenovic
Frontiers Media SA
IntroductionCardiovascular (CV) disorders are steadily increasing, making them the world’s most prevalent health issue. New research highlights the importance of insulin-like growth factor 1 (IGF-1) for maintaining CV healthMethodsWe searched PubMed and MEDLINE for English and non-English articles with English abstracts published between 1957 (when the first report on IGF-1 identification was published) and 2022. The top search terms were: IGF-1, cardiovascular disease, IGF-1 receptors, IGF-1 and microRNAs, therapeutic interventions with IGF-1, IGF-1 and diabetes, IGF-1 and cardiovascular disease. The search retrieved original peer-reviewed articles, which were further analyzed, focusing on the role of IGF-1 in pathophysiological conditions. We specifically focused on including the most recent findings published in the past five years.ResultsIGF-1, an anabolic growth factor, regulates cell division, proliferation, and survival. In addition to its well-known growth-promoting and metabolic effects, there is mounting evidence that IGF-1 plays a specialized role in the complex activities that underpin CV function. IGF-1 promotes cardiac development and improves cardiac output, stroke volume, contractility, and ejection fraction. Furthermore, IGF-1 mediates many growth hormones (GH) actions. IGF-1 stimulates contractility and tissue remodeling in humans to improve heart function after myocardial infarction. IGF-1 also improves the lipid profile, lowers insulin levels, increases insulin sensitivity, and promotes glucose metabolism. These findings point to the intriguing medicinal potential of IGF-1. Human studies associate low serum levels of free or total IGF-1 with an increased risk of CV and cerebrovascular illness. Extensive human trials are being conducted to investigate the therapeutic efficacy and outcomes of IGF-1-related therapy.DiscussionWe anticipate the development of novel IGF-1-related therapy with minimal side effects. This review discusses recent findings on the role of IGF-1 in the cardiovascular (CVD) system, including both normal and pathological conditions. We also discuss progress in therapeutic interventions aimed at targeting the IGF axis and provide insights into the epigenetic regulation of IGF-1 mediated by microRNAs.
Mirjana T. Macvanin, Sonja Zafirovic, Milan Obradovic, and Esma R. Isenovic
Frontiers Media SA
COPYRIGHT © 2023 Macvanin, Zafirovic, Obradovic and Isenovic. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms. TYPE Editorial PUBLISHED 06 February 2023 DOI 10.3389/fendo.2023.1149857
Hind Alamro, Vladan Bajic, Mirjana T. Macvanin, Esma R. Isenovic, Takashi Gojobori, Magbubah Essack, and Xin Gao
Frontiers Media SA
MicroRNAs (miRNAs) are critical regulators of gene expression in healthy and diseased states, and numerous studies have established their tremendous potential as a tool for improving the diagnosis of Type 2 Diabetes Mellitus (T2D) and its comorbidities. In this regard, we computationally identify novel top-ranked hub miRNAs that might be involved in T2D. We accomplish this via two strategies: 1) by ranking miRNAs based on the number of T2D differentially expressed genes (DEGs) they target, and 2) using only the common DEGs between T2D and its comorbidity, Alzheimer’s disease (AD) to predict and rank miRNA. Then classifier models are built using the DEGs targeted by each miRNA as features. Here, we show the T2D DEGs targeted by hsa-mir-1-3p, hsa-mir-16-5p, hsa-mir-124-3p, hsa-mir-34a-5p, hsa-let-7b-5p, hsa-mir-155-5p, hsa-mir-107, hsa-mir-27a-3p, hsa-mir-129-2-3p, and hsa-mir-146a-5p are capable of distinguishing T2D samples from the controls, which serves as a measure of confidence in the miRNAs’ potential role in T2D progression. Moreover, for the second strategy, we show other critical miRNAs can be made apparent through the disease’s comorbidities, and in this case, overall, the hsa-mir-103a-3p models work well for all the datasets, especially in T2D, while the hsa-mir-124-3p models achieved the best scores for the AD datasets. To the best of our knowledge, this is the first study that used predicted miRNAs to determine the features that can separate the diseased samples (T2D or AD) from the normal ones, instead of using conventional non-biology-based feature selection methods.
Mirjana Macvanin, Z. Gluvić, S. Zafirovic, Xin Gao, M. Essack and E. Isenovic
An imbalance between pro-oxidative and antioxidative cellular mechanisms is oxidative stress (OxS) which may be systemic or organ-specific. Although OxS is a consequence of normal body and organ physiology, severely impaired oxidative homeostasis results in DNA hydroxylation, protein denaturation, lipid peroxidation, and apoptosis, ultimately compromising cells’ function and viability. The thyroid gland is an organ that exhibits both oxidative and antioxidative processes. In terms of OxS severity, the thyroid gland’s response could be physiological (i.e. hormone production and secretion) or pathological (i.e. development of diseases, such as goitre, thyroid cancer, or thyroiditis). Protective nutritional antioxidants may benefit defensive antioxidative systems in resolving pro-oxidative dominance and redox imbalance, preventing or delaying chronic thyroid diseases. This review provides information on nutritional antioxidants and their protective roles against impaired redox homeostasis in various thyroid pathologies. We also review novel findings related to the connection between the thyroid gland and gut microbiome and analyze the effects of probiotics with antioxidant properties on thyroid diseases.
Vladimir S. Samardzic, Mirjana T. Macvanin, Sonja S. Zafirovic, Milan M. Obradovic, Zoran M. Gluvic, Jasmina Grubin, Xin Gao, Magbubah Essack, and Esma R. Isenovic
Frontiers Media SA
BackgroundThyroid nodules (TN) are localized morphological changes in the thyroid gland and can be benign or malignant.ObjectiveThe present study investigates the relationships between biochemical markers in serum (s) and their homologs in washout (w) after fine-needle aspiration biopsy (FNAB) of the TN of interest and their correlation with cytology specimen findings.MethodsWe investigated the relationships between serum biochemical markers nitric oxide (NO), thyroglobulin (TG), and calcitonin (CT), their homologs in washout after FNAB of the TN of interest, and cytology findings of biopsy samples classified according to the Bethesda system for thyroid cytopathology in this study, which included 86 subjects.ResultsWashout TG (TGw) level positively correlates with the cytology finding of the biopsy. A higher level of TGw correlates with higher categories of the Bethesda classification and indicates a higher malignant potential. The levels of serum NO (NOs), serum TG (TGs), serum CT (CTs), and washout CT (CTw) do not correlate with the cytology finding of the biopsy, and the higher levels of washout NO (NOw) correspond to the more suspicious ultrasound findings.ConclusionThe findings of our study suggest that TGw and NOw could be used as potential predictors of malignancy in TN.
Mirjana T. Macvanin, Zoran M. Gluvic, Bozidarka L. Zaric, Magbubah Essack, Xin Gao, and Esma R. Isenovic
Frontiers Media SA
After the metabolic syndrome and its components, thyroid disorders represent the most common endocrine disorders, with increasing prevalence in the last two decades. Thyroid dysfunctions are distinguished by hyperthyroidism, hypothyroidism, or inflammation (thyroiditis) of the thyroid gland, in addition to the presence of thyroid nodules that can be benign or malignant. Thyroid cancer is typically detected via an ultrasound (US)-guided fine-needle aspiration biopsy (FNAB) and cytological examination of the specimen. This approach has significant limitations due to the small sample size and inability to characterize follicular lesions adequately. Due to the rapid advancement of high-throughput molecular biology techniques, it is now possible to identify new biomarkers for thyroid neoplasms that can supplement traditional imaging modalities in postoperative surveillance and aid in the preoperative cytology examination of indeterminate or follicular lesions. Here, we review current knowledge regarding biomarkers that have been reliable in detecting thyroid neoplasms, making them valuable tools for assessing the efficacy of surgical procedures or adjunctive treatment after surgery. We are particularly interested in providing an up-to-date and systematic review of emerging biomarkers, such as mRNA and non-coding RNAs, that can potentially detect thyroid neoplasms in clinical settings. We discuss evidence for miRNA, lncRNA and circRNA dysregulation in several thyroid neoplasms and assess their potential for use as diagnostic and prognostic biomarkers.
Mirjana T. Macvanin, Zoran Gluvic, Jelena Radovanovic, Magbubah Essack, Xin Gao, and Esma R. Isenovic
Frontiers Media SA
Diabetes mellitus (DM) is on the rise, necessitating the development of novel therapeutic and preventive strategies to mitigate the disease’s debilitating effects. Diabetic cardiomyopathy (DCMP) is among the leading causes of morbidity and mortality in diabetic patients globally. DCMP manifests as cardiomyocyte hypertrophy, apoptosis, and myocardial interstitial fibrosis before progressing to heart failure. Evidence suggests that non-coding RNAs, such as long non-coding RNAs (lncRNAs) and microRNAs (miRNAs), regulate diabetic cardiomyopathy-related processes such as insulin resistance, cardiomyocyte apoptosis and inflammation, emphasizing their heart-protective effects. This paper reviewed the literature data from animal and human studies on the non-trivial roles of miRNAs and lncRNAs in the context of DCMP in diabetes and demonstrated their future potential in DCMP treatment in diabetic patients.
Mirjana Macvanin, Milan Obradovic, Sonja Zafirovic, Julijana Stanimirovic, and Esma R. Isenovic
Bentham Science Publishers Ltd.
Abstract: Metabolic diseases such as obesity, diabetes, dyslipidemia, and insulin resistance are characterized by glucose and lipid metabolism alterations and represent a global health problem. Many studies have established the crucial role of micro-ribonucleic acids (miRNAs) in controlling metabolic processes in various tissues. miRNAs are single- stranded, highly conserved non-coding RNAs containing 20-24 oligonucleotides that are expressed in a tissue-specific manner. miRNAs mainly interact through base pairing with 3' untranslated regions of target gene mRNAs to promote inhibition of their translation. miRNAs regulate the expression of as many as 30% of the human genes and have a role in crucial physiological processes such as human growth and development, cell proliferation, apoptosis, and metabolism. The number of miRNA molecules with a confirmed role in the pathogenesis of metabolic diseases is quickly expanding due to the availability of high-throughput methodologies for their identification. In this review, we present recent findings regarding the role of miRNAs as endocrine signaling molecules involved in the regulation of insulin production and fat metabolism. We discuss the potential of extracellular miRNAs present in biological fluids miRNAs as biomarkers for the prediction of diabetes and MetS. We also give an updated overview of therapeutic interventions based on antisense oligonucleotides and the CRISPR/Cas9 editing platform for manipulating levels of miRNAs involved in metabolic disorders.
Bozidarka L. Zaric, Mirjana T. Macvanin, and Esma R. Isenovic
Elsevier BV
Mirjana T. Macvanin, Julijana Stanimirovic, and Esma R. Isenovic
Bentham Science Publishers Ltd.
Abstract: Timely and accurate evaluation of clinical parameters associated with endothelial dysfunction is critical in diagnosing and treating atherosclerosis, which represents a severe health problem, accounting for at least 30% of deaths globally. A critical early event in the pathogenesis of atherosclerosis is the oxidative modification of low-density lipoprotein [LDL]. Oxidized LDL [OxLDL] represents numerous changes in lipid and apolipoprotein B [apo B] fractions of LDLs generated by lipid peroxidation. Another critical indicator of perturbed vascular homeostasis is homocysteine [Hcy], an amino acid containing sulfhydryl-group, an intermediate methionine and cysteine biosynthesis product. The total level of Hcy in plasma correlates better than cholesterol with the risk of cardiovascular disease. In addition, nitric oxide [NO] plays an essential role in regulating vascular physiological homeostasis due to its involvement in intravascular free radical and oxidant reactions. Reduced NO decreases oxidative stress in the vascular wall, which reduces the rate of LDL oxidation and the expression of redox-sensitive genes involved in atherogenesis. Endothelial dysfunction is typically associated with increased levels of OxLDL, decreased nitric oxide [NO], and hyperhomocysteinemia. Thus, OxLDL, Hcy, and NO are representative parameters of oxidative stress and endothelial dysfunction. Considering the important role of oxLDL, Hcy and NO in oxidative stress, atherogenesis and accompanying endothelial dysfunction, the challenge of the present work was to systematically present available methods for reliable measurement of these parameters and assess their potential for the use in the clinical setting. Here we present a comprehensive overview of analytical methods for measuring OxLDL, HCy, and NO in biological samples and discuss their advantages and potential problems regarding their application in clinical settings.
Sonja Zafirovic, Mirjana Macvanin, Julijana Stanimirovic, Milan Obradovic, Jelena Radovanovic, Irena Melih, and Esma Isenovic
Bentham Science Publishers Ltd.
Abstract: Telomeres represent the ends of chromosomes, and they are composed of an extensive number of – TTAGGG nucleotide sequence repeats in humans. Telomeres prevent chromosome degradation, participate in stabilization, and regulate the DNA repair system. Inflammation and oxidative stress have been identified as important processes causing cardiovascular disease and accelerating telomere shortening rate. This review investigates the link between telomere length and pathological vascular conditions from experimental and human studies. Also, we discuss pharmacological treatments affecting telomeres and telomerase activity.
Mirjana T. Macvanin, Manfredi Rizzo, Jelena Radovanovic, Alper Sonmez, Francesco Paneni, and Esma R. Isenovic
MDPI AG
(1) Background: Obesity is closely connected to the pathophysiology of cardiovascular diseases (CVDs). Excess fat accumulation is associated with metabolic malfunctions that disrupt cardiovascular homeostasis by activating inflammatory processes that recruit immune cells to the site of injury and reduce nitric oxide levels, resulting in increased blood pressure, endothelial cell migration, proliferation, and apoptosis. Adipose tissue produces adipokines, such as chemerin, that may alter immune responses, lipid metabolism, vascular homeostasis, and angiogenesis. (2) Methods: We performed PubMed and MEDLINE searches for articles with English abstracts published between 1997 (when the first report on chemerin identification was published) and 2022. The search retrieved original peer-reviewed articles analyzed in the context of the role of chemerin in CVDs, explicitly focusing on the most recent findings published in the past five years. (3) Results: This review summarizes up-to-date findings related to mechanisms of chemerin action, its role in the development and progression of CVDs, and novel strategies for developing chemerin-targeting therapeutic agents for treating CVDs. (4) Conclusions: Extensive evidence points to chemerin’s role in vascular inflammation, angiogenesis, and blood pressure modulation, which opens up exciting perspectives for developing chemerin-targeting therapeutic agents for the treatment of CVDs.
Milan R. Nikolic, Simeon Minic, Mirjana Macvanin, Dragana Stanic-Vucinic, and Tanja Cirkovic Velickovic
Springer International Publishing
Tamara N. Uzelac, Aleksandra L. Nikolić-Kokić, Snežana D. Spasić, Mirjana T. Mačvanin, Milan R. Nikolić, Ljuba M. Mandić, and Vesna B. Jovanović
Elsevier BV
Zhong Qian, Mirjana Macvanin, Emilios K. Dimitriadis, Ximiao He, Victor Zhurkin, and Sankar Adhya
American Society for Microbiology
ABSTRACT Repeated extragenic palindromes ( REP s) in the enterobacterial genomes are usually composed of individual palindromic units separated by linker sequences. A total of 355 annotated REP s are distributed along the Escherichia coli genome. RNA sequence (RNAseq) analysis showed that almost 80% of the REP s in E. coli are transcribed. The DNA sequence of REP 325 showed that it is a cluster of six repeats, each with two palindromic units capable of forming cruciform structures in supercoiled DNA. Here, we report that components of the REP 325 element and at least one of its RNA products play a role in bacterial nucleoid DNA condensation. These RNA not only are present in the purified nucleoid but bind to the bacterial nucleoid-associated HU protein as revealed by RNA IP followed by microarray analysis (RIP-Chip) assays. Deletion of REP 325 resulted in a dramatic increase of the nucleoid size as observed using transmission electron microscopy (TEM), and expression of one of the REP 325 RNAs, nucleoid-associated noncoding RNA 4 (naRNA4), from a plasmid restored the wild-type condensed structure. Independently, chromosome conformation capture (3C) analysis demonstrated physical connections among various REP elements around the chromosome. These connections are dependent in some way upon the presence of HU and the REP 325 element; deletion of HU genes and/or the REP 325 element removed the connections. Finally, naRNA4 together with HU condensed DNA in vitro by connecting REP 325 or other DNA sequences that contain cruciform structures in a pairwise manner as observed by atomic force microscopy (AFM). On the basis of our results, we propose molecular models to explain connections of remote cruciform structures mediated by HU and naRNA4. IMPORTANCE Nucleoid organization in bacteria is being studied extensively, and several models have been proposed. However, the molecular nature of the structural organization is not well understood. Here we characterized the role of a novel nucleoid-associated noncoding RNA, naRNA4, in nucleoid structures both in vivo and in vitro . We propose models to explain how naRNA4 together with nucleoid-associated protein HU connects remote DNA elements for nucleoid condensation. We present the first evidence of a noncoding RNA together with a nucleoid-associated protein directly condensing nucleoid DNA.
Mirjana Macvanin, Rotem Edgar, Feng Cui, Andrei Trostel, Victor Zhurkin, and Sankar Adhya
American Society for Microbiology
ABSTRACT Some unidentified RNA molecules, together with the nucleoid protein HU, were suggested to be involved in the nucleoid structure of Escherichia coli . HU is a conserved protein known for its role in binding to DNA and maintaining negative supercoils in the latter. HU also binds to a few RNAs, but the full spectrum of its binding targets in the cell is not known. To understand any interaction of HU with RNA in the nucleoid structure, we immunoprecipitated potential HU-RNA complexes from cells and examined bound RNAs by hybridization to whole-genome tiling arrays. We identified associations between HU and 10 new intragenic and intergenic noncoding RNAs (ncRNAs), 2 of which are homologous to the annotated bacterial interspersed mosaic elements (BIMEs) and boxC DNA repeat elements. We confirmed direct binding of HU to BIME RNA in vitro . We also studied the nucleoid shape of HU and two of the ncRNA mutants (nc1 and nc5) by transmission electron microscopy and showed that both HU and the two ncRNAs play a role in nucleoid morphology. We propose that at least two of the ncRNA species complex with HU and help the formation or maintenance of the architecture of the E. coli chromosome. We also observed binding of HU with rRNA and tRNA segments, a few small RNAs, and a distinct small set of mRNAs, although the significance, if any, of these associations is not known.
Mirjana Macvanin and Sankar Adhya
Elsevier BV
Diarmaid Hughes and Mirjana Macvanin
Humana Press
Mirjana Macvanin and Diarmaid Hughes
Humana Press
Mirjana Mačvanin, Ernesto I. Gonzalez de Valdivia, David H. Ardell, and Leif A. Isaksson
American Society for Microbiology
ABSTRACT Expression of minigenes encoding tetra- or pentapeptides MXLX or MXLXV (E peptides), where X is a nonpolar amino acid, renders cells erythromycin resistant whereas expression of minigenes encoding tripeptide MXL does not. By using a 3A′ reporter gene system beginning with an E-peptide-encoding sequence, we asked whether the codons UGG and GGG, which are known to promote peptidyl-tRNA drop-off at early positions in mRNA, would result in a phenotype of erythromycin resistance if located after this sequence. We find that UGG or GGG, at either position +4 or +5, without a following stop codon, is associated with an erythromycin resistance phenotype upon gene induction. Our results suggest that, while a stop codon at +4 gives a tripeptide product (MIL) and erythromycin sensitivity, UGG or GGG codons at the same position give a tetrapeptide product (MILW or MILG) and phenotype of erythromycin resistance. Thus, the drop-off event on GGG or UGG codons occurs after incorporation of the corresponding amino acid into the growing peptide chain. Drop-off gives rise to a peptidyl-tRNA where the peptide moiety functionally mimics a minigene peptide product of the type previously associated with erythromycin resistance. Several genes in Escherichia coli fulfill the requirements of high mRNA expression and an E-peptide sequence followed by UGG or GGG at position +4 or +5 and should potentially be able to give an erythromycin resistance phenotype.
Mirjana Macvanin and Diarmaid Hughes
Oxford University Press (OUP)
Mirjana Macvanin, Andras Ballagi, and Diarmaid Hughes
American Society for Microbiology
ABSTRACT Mutations in the translation elongation factor G (EF-G) make Salmonella enterica serovar Typhimurium resistant to the antibiotic fusidic acid. Fus r mutants are hypersensitive to oxidative stress and rapidly lose viability in the presence of hydrogen peroxide. We show that this phenotype is associated with reduced activity of two catalase enzymes, HPI (a bifunctional catalase-hydroperoxidase) and HPII (a monofunctional catalase). These catalases require the iron-binding cofactor heme for their activity. Fus r mutants have a reduced rate of transcription of hemA , a gene whose product catalyzes the first committed step in heme biosynthesis. Hypersensitivity of Fus r mutants to hydrogen peroxide is abolished by the presence of δ-aminolevulinic acid, the precursor of heme synthesis, in the growth media and by the addition of glutamate or glutamine, amino acids required for the first step in heme biosynthesis. Fluorescence measurements show that the level of heme in a Fus r mutant is significantly lower than it is in the wild type. Heme is also an essential cofactor of cytochromes in the electron transport chain of respiration. We found that the rate of respiration is reduced significantly in Fus r mutants. Sequestration of divalent iron in the growth media decreases the sensitivity of Fus r mutants to oxidative stress. Taken together, these results suggest that Fus r mutants are hypersensitive to oxidative stress because their low levels of heme reduce both catalase activity and respiration capacity. The sensitivity of Fus r mutants to oxidative stress could be associated with loss of viability due to iron-mediated DNA damage in the presence of hydrogen peroxide. We argue that understanding the specific nature of antibiotic resistance fitness costs in different environments may be a generally useful approach in identifying physiological processes that could serve as novel targets for antimicrobial agents.