Also published as: A.R. Kim, B Kim, B-E Kim, B. Kim, BS Kim, C. Kim, C.H. Kim, Chun Kim, D Kim, D. Kim, D.-K. Kim, D.G. Kim, D.K. Kim, DD Kim, DH Kim, DK Kim, DW Kim, Do-Hyung Kim, Dongwook Kim, E Kim, E. Kim, E.L. Kim, EH Kim, EJ Kim, ET Kim, Eun Hye Kim, Eun-Hee Kim, Eunkyoung Kim, G Kim, Geun Hoe Kim, H D Kim, H Kim, H. D. Kim, H. Kim, H. R. Kim, H. S. Kim, H.D. Kim, H.K. Kim, H.S. Kim, HJ Kim, HK Kim, HS Kim, Heechan Kim, Hyung J Kim, Hyunwoo Kim, I.H. Kim, IH Kim, IK Kim, J Kim, J. Kim, J.H. Kim, J.Y. Kim, JD Kim, JK Kim, JW Kim, JY Kim, Jae Hyun Kim, Jeong-Dong Kim, Jong H. Kim, Jong Hyun Kim, Jong Seung Kim, K. B. Kim, K. Kim, K. S. Kim, K. Y. Kim, K.‐W. Kim, KB Kim, KJ Kim, KK Kim, Kyeong Kyu Kim, Kyoung Eun Kim, M Kim, M-J Kim, M. Kim, M.A. Kim, M.H. Kim, M.S. Kim, MM Kim, MS Kim, MY Kim, Minjung Kim, Myeong Gyu Kim, N Kim, N-K Kim, ND Kim, NH Kim, Na-Hyun Kim, Nathan Kim, P Kim, Q. Kim, R-K Kim, S H Kim, S Kim, S. G. Kim, S. H. Kim, S. Kim, S. Y. Kim, S.H. Kim, S.J. Kim, S.L. Kim, S.S. Kim, S.W. Kim, SG Kim, SJ Kim, SM Kim, SR Kim, SW Kim, SY Kim, Seon Hee Kim, Seungil Kim, Sook Ho Kim, Sungdo Kim, T Kim, T S Kim, T. S. Kim, T.H. Kim, TG Kim, TJ Kim, TW Kim, U Kim, V. V. Kim, W Kim, W. K. Kim, WG Kim, WY Kim, Won Kim, Woo Youn Kim, Y G Kim, Y Kim, Y-H Kim, Y-S Kim, Y. Kim, Y.H. Kim, YB Kim, YG Kim, YH Kim, YJ Kim, YK Kim, YM Kim, Yong-Joo Kim
Platinum-based anticancer drugs represented by cisplatin play important roles in the treatment of various solid tumors. However, their applications are largely compromised by drug resistance and side Show more
Platinum-based anticancer drugs represented by cisplatin play important roles in the treatment of various solid tumors. However, their applications are largely compromised by drug resistance and side effects. Much effort has been made to circumvent the drug resistance and general toxicity of these drugs. Among multifarious designs, monofunctional platinum(II) complexes with a general formula of [Pt(3A)Cl] + (A: Ammonia or amine) stand out as a class of “non-traditional” anticancer agents hopeful to overcome the defects of current platinum drugs. This review aims to summarize the development of monofunctional platinum(II) complexes in recent years. They are classified into four categories: fluorescent complexes, photoactive complexes, targeted complexes, and miscellaneous complexes. The intention behind the designs is either to visualize the cellular distribution, or to reduce the side effects, or to improve the tumor selectivity, or inhibit the cancer cells through non-DNA targets. The information provided by this review may inspire researchers to conceive more innovative complexes with potent efficacy to shake off the drawbacks of platinum anticancer drugs. Show less
Simple Summary The gene-regulatory factors ATF5, CEBPB and CEBPD promote survival, growth, metastasis and treatment resistance of a range of cancer cell types. Presently, no drugs target all three at Show more
Simple Summary The gene-regulatory factors ATF5, CEBPB and CEBPD promote survival, growth, metastasis and treatment resistance of a range of cancer cell types. Presently, no drugs target all three at once. Here, with the aim of treating cancers, we designed novel cell-penetrating peptides that interact with and inactivate all three. The peptides Bpep and Dpep kill a range of cancer cell types in culture and in animals. In animals with tumors, they also significantly increase survival time. In contrast, they do not affect survival of non-cancer cells and have no apparent side effects in animals. The peptides work in combination with other anti-cancer treatments. Mechanism studies of how the peptides kill cancer cells indicate a decrease in survival proteins and increase in death proteins. These studies support the potential of Bpep and Dpep as novel, safe agents for the treatment of a variety of cancer types, both as mono- and combination therapies. Abstract Transcription factors are key players underlying cancer formation, growth, survival, metastasis and treatment resistance, yet few drugs exist to directly target them. Here, we characterized the in vitro and in vivo anti-cancer efficacy of novel synthetic cell-penetrating peptides (Bpep and Dpep) designed to interfere with the formation of active leucine-zipper-based dimers by CEBPB and CEBPD, transcription factors implicated in multiple malignancies. Both peptides similarly promoted apoptosis of multiple tumor lines of varying origins, without such effects on non-transformed cells. Combined with other treatments (radiation, Taxol, chloroquine, doxorubicin), the peptides acted additively to synergistically and were fully active on Taxol-resistant cells. The peptides suppressed expression of known direct CEBPB/CEBPD targets IL6 , IL8 and asparagine synthetase ( ASNS ), supporting their inhibition of transcriptional activation. Mechanisms by which the peptides trigger apoptosis included depletion of pro-survival survivin and a required elevation of pro-apoptotic BMF. Bpep and Dpep significantly slowed tumor growth in mouse models without evident side effects. Dpep significantly prolonged survival in xenograft models. These findings indicate the efficacy and potential of Bpep and Dpep as novel agents to treat a variety of cancers as mono- or combination therapies. Show less
Despite recent genome-wide investigations of functional DNA elements, the mechanistic details about their actions remain elusive. One intriguing possibility is that DNA sequences with special patterns Show more
Despite recent genome-wide investigations of functional DNA elements, the mechanistic details about their actions remain elusive. One intriguing possibility is that DNA sequences with special patterns play biological roles, adopting non-B-DNA conformations. Here we investigated dynamics of thymine-guanine (TG) repeats, microsatellite sequences and recurrently found in promoters, as well as cytosine-guanine (CG) repeats, best-known Z-DNA forming sequence, in the aspect of Z-DNA formation. We measured the energy barriers of the B-Z transition with those repeats and discovered the sequence-dependent penalty for Z-DNA generates distinctive thermodynamic and kinetic features in the torque-induced transition. Due to the higher torsional stress required for Z-form in TG repeats, a bubble could be induced more easily, suppressing Z-DNA induction, but facilitate the B-Z interconversion kinetically at the transition midpoint. Thus, the Z-form by TG repeats has advantages as a torsion buffer and bubble selector while the Z-form by CG repeats likely behaves as torsion absorber. Our statistical physics model supports quantitatively the populations of Z-DNA and reveals the pivotal roles of bubbles in state dynamics. All taken together, a quantitative picture for the transition was deduced within the close interplay among bubbles, plectonemes and Z-DNA. Show less
Mitochondrial structure and organization is integral to maintaining mitochondrial homeostasis and an emerging biological target in aging, inflammation, neurodegeneration, and cancer. The study of mito Show more
Mitochondrial structure and organization is integral to maintaining mitochondrial homeostasis and an emerging biological target in aging, inflammation, neurodegeneration, and cancer. The study of mitochondrial structure and its functional implications remains challenging in part because of the lack of available tools for direct engagement, particularly in a disease setting. Here, we report a gold-based approach to perturb mitochondrial structure in cancer cells. Specifically, the design and synthesis of a series of tricoordinate Au(I) complexes with systematic modifications to group 15 nonmetallic ligands establish structure-activity relationships (SAR) to identify physiologically relevant tools for mitochondrial perturbation. The optimized compound, AuTri-9 selectively disrupts breast cancer mitochondrial structure rapidly as observed by transmission electron microscopy with attendant effects on fusion and fission proteins. This phenomenon triggers severe depolarization of the mitochondrial membrane in cancer cells. The high in vivo tolerability of AuTri-9 in mice demonstrates its preclinical utility. This work provides a basis for rational design of gold-based agents to control mitochondrial structure and dynamics. Show less
The right-handed double-helical structure of DNA (B-DNA), which follows the Watson-Crick model, is the canonical form of DNA existing in normal physiological settings. Even though an alternative left- Show more
The right-handed double-helical structure of DNA (B-DNA), which follows the Watson-Crick model, is the canonical form of DNA existing in normal physiological settings. Even though an alternative left-handed structure of DNA (Z-DNA) was discovered in the late 1970s, Z-form nucleic acid has not received much attention from biologists, because it is extremely unstable under physiological conditions, has an ill-defined mechanism of its formation, and has obscure biological functions. The debate about the physiological relevance of Z-DNA was settled only after a class of proteins was found to potentially recognize the Z-form architecture of DNA. Interestingly, these Z-DNA binding proteins can bind not only the left-handed form of DNA but also the equivalent structure of RNA (Z-RNA). The Z-DNA/RNA binding proteins present from viruses to humans function as important regulators of biological processes. In particular, the proteins ADAR1 and ZBP1 are currently being extensively re-evaluated in the field to understand potential roles of the noncanonical Z-conformation of nucleic acids in host immune responses and human disease. Despite a growing body of evidence supporting the biological importance of Z-DNA/RNA, there remain many unanswered principal questions, such as when Z-form nucleic acids arise and how they signal to downstream pathways. Understanding Z-DNA/RNA and the sensors in different pathophysiological conditions will widen our view on the regulation of immune responses and open a new door of opportunity to develop novel types of immunomodulatory therapeutic possibilities. [BMB Reports 2020; 53(9): 453-457]. Show less
The crystal structure of BZ-junction reveals that left-handed Z-DNA stabilized by Z-DNA binding domain (Zα) is continuously stacked to right-handed B-DNA with AT bases' extrusion in the junction site. Show more
The crystal structure of BZ-junction reveals that left-handed Z-DNA stabilized by Z-DNA binding domain (Zα) is continuously stacked to right-handed B-DNA with AT bases' extrusion in the junction site. However, this structure might not fully represent the BZ-junction in solution due to the possibility of the junction formation either by crystal packing or Zα interaction. Therefore, we investigated BZ-junction in solution with chemical Z-DNA inducers using CD and 2-aminopurine base-extrusion assay. We confirmed the formation of Z-DNA and BZ-junction with base-extrusion by chemical Z-DNA inducers. However, neither typical Z-DNA nor base-extrusion could be detected with some inducers such as spermine, suggesting that the energy barrier for the formation of the BZ junction might vary depending on the Z-DNA induction conditions. Show less
The scope of studies investigating the architecture of genomic DNA has progressed steadily since the elucidation of the structure of B-DNA. In recent years, several non-canonical DNA structures includ Show more
The scope of studies investigating the architecture of genomic DNA has progressed steadily since the elucidation of the structure of B-DNA. In recent years, several non-canonical DNA structures including Z-DNA, G-quadruplexes, H-DNA, cruciform DNA, and i-motifs have been reported to form in genomic DNA and are closely related to the evolution and development of disease. The ability of these structures to form in genomic DNA indicates that they might have important cellular roles and are therefore retained during evolution. Understanding the impact of the formation of these secondary structures on cellular processes can enable identification of new targets for therapeutics. In this review, we report the state of understanding of Z-DNA structure and formation and their implication in disease. Finally, we state our perspective on the potential of Z-DNA as a therapeutic target. Show less
Left-handed Z-DNA/Z-RNA is bound with high affinity by the Zα domain protein family that includes ADAR (a double-stranded RNA editing enzyme), ZBP1 and viral orthologs regulating innate immunity. Loss Show more
Left-handed Z-DNA/Z-RNA is bound with high affinity by the Zα domain protein family that includes ADAR (a double-stranded RNA editing enzyme), ZBP1 and viral orthologs regulating innate immunity. Loss-of-function mutations in ADAR p150 allow persistent activation of the interferon system by Alu dsRNAs and are causal for Aicardi-Goutières Syndrome. Heterodimers of ADAR and DICER1 regulate the switch from RNA- to protein-centric immunity. Loss of DICER1 function produces age-related macular degeneration, a different type of Alu-mediated disease. The overlap of Z-forming sites with those for the signal recognition particle likely limits invasion of primate genomes by Alu retrotransposons. Show less
Accumulating evidence suggests that aerobic glycolysis is important for colorectal cancer (CRC) development. However, the underlying mechanisms have yet to be elucidated. B7-H3, an immunoregulatory pr Show more
Accumulating evidence suggests that aerobic glycolysis is important for colorectal cancer (CRC) development. However, the underlying mechanisms have yet to be elucidated. B7-H3, an immunoregulatory protein, is broadly overexpressed by multiple tumor types and plays a vital role in tumor progression. In this study, we found that overexpression of B7-H3 effectively increased the rate of glucose consumption and lactate production, whereas knockdown of B7-H3 had the opposite effect. Furthermore, we showed that B7-H3 increased glucose consumption and lactate production by promoting hexokinase 2 (HK2) expression in CRC cells, and we also found that HK2 was a key mediator of B7-H3-induced CRC chemoresistance. Depletion of HK2 expression or treating cells with HK2 inhibitors could reverse the B7-H3-induced increase in aerobic glycolysis and B7-H3-endowed chemoresistance of cancer cells. Moreover, we verified a positive correlation between the expression of B7-H3 and HK2 in tumor tissues of CRC patients. Collectively, our findings suggest that B7-H3 may be a novel regulator of glucose metabolism and chemoresistance via controlling HK2 expression in CRC cells, a result that could help develop B7-H3 as a promising therapeutic target for CRC treatment. Show less
Abstract TFIIH is a 10‐subunit complex that regulates RNA polymerase II (pol II) transcription but also serves other important biological roles. Although much remains unknown about TFIIH function in Show more
Abstract TFIIH is a 10‐subunit complex that regulates RNA polymerase II (pol II) transcription but also serves other important biological roles. Although much remains unknown about TFIIH function in eukaryotic cells, much progress has been made even in just the past few years, due in part to technological advances (e.g. cryoEM and single molecule methods) and the development of chemical inhibitors of TFIIH enzymes. This review focuses on the major cellular roles for TFIIH, with an emphasis on TFIIH function as a regulator of pol II transcription. We describe the structure of TFIIH and its roles in pol II initiation, promoter‐proximal pausing, elongation, and termination. We also discuss cellular roles for TFIIH beyond transcription (e.g. DNA repair, cell cycle regulation) and summarize small molecule inhibitors of TFIIH and diseases associated with defects in TFIIH structure and function. Show less
Abstract Significance: Mitochondria are the energetic, metabolic, redox, and information signaling centers of the cell. Substrate pressure, mitochondrial network dynamics, and cristae morphology Show more
Abstract Significance: Mitochondria are the energetic, metabolic, redox, and information signaling centers of the cell. Substrate pressure, mitochondrial network dynamics, and cristae morphology state are integrated by the protonmotive force Δ p or its potential component, Δ Ψ , which are attenuated by proton backflux into the matrix, termed uncoupling. The mitochondrial uncoupling proteins (UCP1–5) play an eminent role in the regulation of each of the mentioned aspects, being involved in numerous physiological events including redox signaling. Recent Advances: UCP2 structure, including purine nucleotide and fatty acid (FA) binding sites, strongly support the FA cycling mechanism: UCP2 expels FA anions, whereas uncoupling is achieved by the membrane backflux of protonated FA. Nascent FAs, cleaved by phospholipases, are preferential. The resulting Δ p dissipation decreases superoxide formation dependent on Δ p . UCP-mediated antioxidant protection and its impairment are expected to play a major role in cell physiology and pathology. Moreover, UCP2-mediated aspartate, oxaloacetate, and malate antiport with phosphate is expected to alter metabolism of cancer cells. Critical Issues: A wide range of UCP antioxidant effects and participations in redox signaling have been reported; however, mechanisms of UCP activation are still debated. Switching off/on the UCP2 protonophoretic function might serve as redox signaling either by employing/releasing the extra capacity of cell antioxidant systems or by directly increasing/decreasing mitochondrial superoxide sources. Rapid UCP2 degradation, FA levels, elevation of purine nucleotides, decreased Mg 2+ , or increased pyruvate accumulation may initiate UCP-mediated redox signaling. Future Directions: Issues such as UCP2 participation in glucose sensing, neuronal (synaptic) function, and immune cell activation should be elucidated. Antioxid. Redox Signal. 29, 667–714. Show less
Z-DNA is stabilized by various Z-DNA binding proteins (ZBPs) that play important roles in RNA editing, innate immune response, and viral infection. In this review, the structural and dynamics of vario Show more
Z-DNA is stabilized by various Z-DNA binding proteins (ZBPs) that play important roles in RNA editing, innate immune response, and viral infection. In this review, the structural and dynamics of various ZBPs complexed with Z-DNA are summarized to better understand the mechanisms by which ZBPs selectively recognize d(CG)-repeat DNA sequences in genomic DNA and efficiently convert them to left-handed Z-DNA to achieve their biological function. The intermolecular interaction of ZBPs with Z-DNA strands is mediated through a single continuous recognition surface which consists of an α3 helix and a β-hairpin. In the ZBP-Z-DNA complexes, three identical, conserved residues (N173, Y177, and W195 in the Zα domain of human ADAR1) play central roles in the interaction with Z-DNA. ZBPs convert a 6-base DNA pair to a Z-form helix via the B-Z transition mechanism in which the ZBP first binds to B-DNA and then shifts the equilibrium from B-DNA to Z-DNA, a conformation that is then selectively stabilized by the additional binding of a second ZBP molecule. During B-Z transition, ZBPs selectively recognize the alternating d(CG)n sequence and convert it to a Z-form helix in long genomic DNA through multiple sequence discrimination steps. In addition, the intermediate complex formed by ZBPs and B-DNA, which is modulated by varying conditions, determines the degree of B-Z transition. Show less
UNLABELLED: Artesunate, an anti-malarial drug, has been repurposed as an anticancer drug due to its induction of cell death via reactive oxygen species (ROS) production. However, the molecular mechani Show more
UNLABELLED: Artesunate, an anti-malarial drug, has been repurposed as an anticancer drug due to its induction of cell death via reactive oxygen species (ROS) production. However, the molecular mechanisms regulating cancer cell death and the resistance of cells to artesunate remain unclear. We investigated the molecular mechanisms behind the antitumor effects of artesunate and an approach to overcome artesunate resistance in head and neck cancer (HNC). The effects of artesunate and trigonelline were tested in different HNC cell lines, including three cisplatin-resistant HNC cell lines. The effects of these drugs as well as the inhibition of Keap1, Nrf2, and HO-1 were assessed by cell viability, cell death, glutathione (GSH) and ROS production, protein expression, and mouse tumor xenograft models. Artesunate selectively killed HNC cells but not normal cells. The artesunate sensitivity was relatively low in cisplatin-resistant HNC cells. Artesunate induced ferroptosis in HNC cells by decreasing cellular GSH levels and increasing lipid ROS levels. This effect was blocked by co-incubation with ferrostatin-1 and a trolox pretreatment. Artesunate activated the Nrf2-antioxidant response element (ARE) pathway in HNC cells, which contributed to ferroptosis resistance. The silencing of Keap1, a negative regulator of Nrf2, decreased artesunate sensitivity in HNC cells. Nrf2 genetic silencing or trigonelline reversed the ferroptosis resistance of Keap1-silenced and cisplatin-resistant HNC cells to artesunate in vitro and in vivo. Nrf2-ARE pathway activation contributes to the artesunate resistance of HNC cells, and inhibition of this pathway abolishes ferroptosis-resistant HNC.
CONDENSED ABSTRACT: Our results show the effectiveness and molecular mechanism of artesunate treatment on head and neck cancer (HNC). Artesunate selectively killed HNC cells but not normal cells by inducing an iron-dependent, ROS-accumulated ferroptosis. However, this effect may be suboptimal in some cisplatin-resistant HNCs because of Nrf2-antioxidant response element (ARE) pathway activation. Inhibition of the Nrf2-ARE pathway increased artesunate sensitivity and reversed the ferroptosis resistance in resistant HNC cells. Show less
Highly ordered interactions between immune and metabolic responses are evolutionarily conserved and paramount for tissue and organismal health. Disruption of these interactions underlies the emergence Show more
Highly ordered interactions between immune and metabolic responses are evolutionarily conserved and paramount for tissue and organismal health. Disruption of these interactions underlies the emergence of many pathologies, particularly chronic non-communicable diseases such as obesity and diabetes. Here, we examine decades of research identifying the complex immunometabolic signaling networks and the cellular and molecular events that occur in the setting of altered nutrient and energy exposures and offer a historical perspective. Furthermore, we describe recent advances such as the discovery that a broad complement of immune cells play a role in immunometabolism and the emerging evidence that nutrients and metabolites modulate inflammatory pathways. Lastly, we discuss how this work may eventually lead to tangible therapeutic advancements to promote health. Show less
Mitochondrial Ca 2+ uptake plays a pivotal role both in cell energy balance and in cell fate determination. Studies on the role of mitochondrial Ca 2+ signaling in pathophysiology have been favored Show more
Mitochondrial Ca 2+ uptake plays a pivotal role both in cell energy balance and in cell fate determination. Studies on the role of mitochondrial Ca 2+ signaling in pathophysiology have been favored by the identification of the genes encoding the mitochondrial calcium uniporter (MCU) and its regulatory subunits. Thus, research carried on in the last years on one hand has determined the structure of the MCU complex and its regulation, on the other has uncovered the consequences of dysregulated mitochondrial Ca 2+ signaling in cell and tissue homeostasis. Whether mitochondrial Ca 2+ uptake can be exploited as a weapon to counteract cancer progression is debated. In this review, we summarize recent research on the molecular structure of the MCU, the regulatory mechanisms that control its activity and its relevance in pathophysiology, focusing in particular on its role in cancer progression. Show less
A principal limitation to the clinical use of cisplatin is the high incidence of chemoresistance to this drug. Combination treatments with other drugs may help to circumvent this problem. Wogonin, one Show more
A principal limitation to the clinical use of cisplatin is the high incidence of chemoresistance to this drug. Combination treatments with other drugs may help to circumvent this problem. Wogonin, one of the major natural flavonoids, is known to reverse multidrug resistance in several types of cancers. We investigated the ability of wogonin to overcome cisplatin resistance in head and neck cancer (HNC) cells and further clarified its molecular mechanisms of action. Two cisplatin-resistant HNC cell lines (AMC-HN4R and -HN9R) and their parental and other human HNC cell lines were used. The effects of wogonin, either alone or in combination with cisplatin, were assessed in HNC cells and normal cells using cell cycle and death assays and by measuring cell viability, reactive oxygen species (ROS) production, and protein expression, and in tumor xenograft mouse models. Wogonin selectively killed HNC cells but spared normal cells. It inhibited nuclear factor erythroid 2-related factor 2 and glutathione S-transferase P in cisplatin-resistant HNC cells, resulting in increased ROS accumulation in HNC cells, an effect that could be blocked by the antioxidant N-acetyl-L-cysteine. Wogonin also induced selective cell death by targeting the antioxidant defense mechanisms enhanced in the resistant HNC cells and activating cell death pathways involving PUMA and PARP. Hence, wogonin significantly sensitized resistant HNC cells to cisplatin both in vitro and in vivo. Wogonin is a promising anticancer candidate that induces ROS accumulation and selective cytotoxicity in HNC cells and can help to overcome cisplatin-resistance in this cancer. Show less
The sequential flow of electrons in the respiratory chain, from a low reduction potential substrate to O(2), is mediated by protein-bound redox cofactors. In mitochondria, hemes-together with flavin, Show more
The sequential flow of electrons in the respiratory chain, from a low reduction potential substrate to O(2), is mediated by protein-bound redox cofactors. In mitochondria, hemes-together with flavin, iron-sulfur, and copper cofactors-mediate this multi-electron transfer. Hemes, in three different forms, are used as a protein-bound prosthetic group in succinate dehydrogenase (complex II), in bc(1) complex (complex III) and in cytochrome c oxidase (complex IV). The exact function of heme b in complex II is still unclear, and lags behind in operational detail that is available for the hemes of complex III and IV. The two b hemes of complex III participate in the unique bifurcation of electron flow from the oxidation of ubiquinol, while heme c of the cytochrome c subunit, Cyt1, transfers these electrons to the peripheral cytochrome c. The unique heme a(3), with Cu(B), form a catalytic site in complex IV that binds and reduces molecular oxygen. In addition to providing catalytic and electron transfer operations, hemes also serve a critical role in the assembly of these respiratory complexes, which is just beginning to be understood. In the absence of heme, the assembly of complex II is impaired, especially in mammalian cells. In complex III, a covalent attachment of the heme to apo-Cyt1 is a prerequisite for the complete assembly of bc(1), whereas in complex IV, heme a is required for the proper folding of the Cox 1 subunit and subsequent assembly. In this review, we provide further details of the aforementioned processes with respect to the hemes of the mitochondrial respiratory complexes. This article is part of a Special Issue entitled: Cell Biology of Metals. Show less
In this chapter several aspects of Pt(II) are highlighted that focus on the properties of Pt(II)-RNA adducts and the possibility that they influence RNA-based processes in cells. Cellular distribution Show more
In this chapter several aspects of Pt(II) are highlighted that focus on the properties of Pt(II)-RNA adducts and the possibility that they influence RNA-based processes in cells. Cellular distribution of Pt(II) complexes results in significant platination of RNA, and localization studies find Pt(II) in the nucleus, nucleolus, and a distribution of other sites in cells. Treatment with Pt(II) compounds disrupts RNA-based processes including enzymatic processing, splicing, and translation, and this disruption may be indicative of structural changes to RNA or RNA-protein complexes. Several RNA-Pt(II) adducts have been characterized in vitro by biochemical and other methods. Evidence for Pt(II) binding in non-helical regions and for Pt(II) cross-linking of internal loops has been found. Although platinated sites have been identified, there currently exists very little in the way of detailed structural characterization of RNA-Pt(II) adducts. Some insight into the details of Pt(II) coordination to RNA, especially RNA helices, can be gained from DNA model systems. Many RNA structures, however, contain complex tertiary folds and common, purine-rich structural elements that present suitable Pt(II) nucleophiles in unique arrangements which may hold the potential for novel types of platinum-RNA adducts. Future research aimed at structural characterization of platinum-RNA adducts may provide further insights into platinum-nucleic acid binding motifs, and perhaps provide a rationale for the observed inhibition by Pt(II) complexes of splicing, translation, and enzymatic processing. Show less
Impaired selective turnover of p62 by autophagy causes severe liver injury accompanied by the formation of p62-positive inclusions and upregulation of detoxifying enzymes. These phenotypes correspond Show more
Impaired selective turnover of p62 by autophagy causes severe liver injury accompanied by the formation of p62-positive inclusions and upregulation of detoxifying enzymes. These phenotypes correspond closely to the pathological conditions seen in human liver diseases, including alcoholic hepatitis and hepatocellular carcinoma. However, the molecular mechanisms and pathophysiological processes in these events are still unknown. Here we report the identification of a novel regulatory mechanism by p62 of the transcription factor Nrf2, whose target genes include antioxidant proteins and detoxification enzymes. p62 interacts with the Nrf2-binding site on Keap1, a component of Cullin-3-type ubiquitin ligase for Nrf2. Thus, an overproduction of p62 or a deficiency in autophagy competes with the interaction between Nrf2 and Keap1, resulting in stabilization of Nrf2 and transcriptional activation of Nrf2 target genes. Our findings indicate that the pathological process associated with p62 accumulation results in hyperactivation of Nrf2 and delineates unexpected roles of selective autophagy in controlling the transcription of cellular defence enzyme genes. Show less
Double-stranded RNA adenosine deaminase (ADAR1) is an ubiquitous enzyme in metazoa that edits pre-mRNA changing adenosine to inosine in regions of double-stranded RNA. Zalpha, an N-terminal domain of Show more
Double-stranded RNA adenosine deaminase (ADAR1) is an ubiquitous enzyme in metazoa that edits pre-mRNA changing adenosine to inosine in regions of double-stranded RNA. Zalpha, an N-terminal domain of human ADAR1 encompassing 76 amino acid residues, shows apparent specificity for the left-handed Z-DNA conformation adopted by alternating (dGdC) polymers modified by bromination or methylation, as well as for (dGdC)13 inserts present in supercoiled plasmids. Here, a combination of circular dichroism, fluorescence, and gel-retardation studies is utilized to characterize recombinant Zalpha peptide and to examine its interaction with DNA. Results from laser-Raman spectroscopy experiments provide direct evidence for the existence of Z-DNA in peptide-DNA complexes. Show less