Medicine and Health Sciences Commons^™

Ether Bridge Formation In Loline Alkaloid Biosynthesis, Juan Pan, Minakshi Bhardwaj, Jerome Ralph Faulkner, Padmaja Nagabhyru, Nikki D. Charlton, Richard M. Higashi, Anne-Frances Miller, Carolyn A Young, Robert B. Grossman, Christopher L. Schardl

Toxicology and Cancer Biology Faculty Publications

Lolines are potent insecticidal agents produced by endophytic fungi of cool-season grasses. These alkaloids are composed of a pyrrolizidine ring system and an uncommon ether bridge linking carbons 2 and 7. Previous results indicated that 1-aminopyrrolizidine was a pathway intermediate. We used RNA interference to knock down expression of lolO, resulting in the accumulation of an alkaloid identified as exo-1-acetamidopyrrolizidine based on high-resolution MS and NMR. Genomes of endophytes differing in alkaloid profiles were sequenced, revealing that those with mutated lolO accumulated exo-1-acetamidopyrrolizidine but no lolines. Heterologous expression of wild-type lolO complemented a lolO mutant, resulting in …

Intramolecular Telomeric G-Quadruplexes Dramatically Inhibit Dna Synthesis By Replicative And Translesion Polymerases, Revealing Their Potential To Lead To Genetic Change, Deanna N. Edwards, Amrita Machwe, Zhigang Wang, David K. Orren

Toxicology and Cancer Biology Faculty Publications

Recent research indicates that hundreds of thousands of G-rich sequences within the human genome have the potential to form secondary structures known as G-quadruplexes. Telomeric regions, consisting of long arrays of TTAGGG/AATCCC repeats, are among the most likely areas in which these structures might form. Since G-quadruplexes assemble from certain G-rich single-stranded sequences, they might arise when duplex DNA is unwound such as during replication. Coincidentally, these bulky structures when present in the DNA template might also hinder the action of DNA polymerases. In this study, single-stranded telomeric templates with the potential to form G-quadruplexes were examined for their effects …

Strand Exchange Of Telomeric Dna Catalyzed By The Werner Syndrome Protein (Wrn) Is Specifically Stimulated By Trf2, Deanna Edwards, David K. Orren, Amrita Machwe

Toxicology and Cancer Biology Faculty Publications

Werner syndrome (WS), caused by loss of function of the RecQ helicase WRN, is a hereditary disease characterized by premature aging and elevated cancer incidence. WRN has DNA binding, exonuclease, ATPase, helicase and strand annealing activities, suggesting possible roles in recombination-related processes. Evidence indicates that WRN deficiency causes telomeric abnormalities that likely underlie early onset of aging phenotypes in WS. Furthermore, TRF2, a protein essential for telomere protection, interacts with WRN and influences its basic helicase and exonuclease activities. However, these studies provided little insight into WRN's specific function at telomeres. Here, we explored the possibility that WRN and TRF2 …

Mismatch Repair Genes Mlh1 And Mlh3 Modify Cag Instability In Huntington's Disease Mice: Genome-Wide And Candidate Approaches, Ricardo Mouro Pinto, Ella Dragileva, Andrew Kirby, Alejandro Lloret, Edith Lopez, Jason St. Claire, Gagan B. Panigrahi, Caixia Hou, Kim Holloway, Tammy Gillis, Jolene R. Guide, Paula E. Cohen, Guo-Min Li, Christopher E. Pearson, Mark J. Daly, Vanessa C. Wheeler

Toxicology and Cancer Biology Faculty Publications

The Huntington's disease gene (HTT) CAG repeat mutation undergoes somatic expansion that correlates with pathogenesis. Modifiers of somatic expansion may therefore provide routes for therapies targeting the underlying mutation, an approach that is likely applicable to other trinucleotide repeat diseases. Huntington's disease Hdh(Q111) mice exhibit higher levels of somatic HTT CAG expansion on a C57BL/6 genetic background (B6.Hdh(Q111) ) than on a 129 background (129.Hdh(Q111) ). Linkage mapping in (B6x129).Hdh(Q111) F2 intercross animals identified a single quantitative trait locus underlying the strain-specific difference in expansion in the striatum, implicating mismatch repair (MMR) gene Mlh1 as the most likely candidate modifier. …

Proteomic Analysis Of Mismatch Repair-Mediated Alkylating Agent-Induced Dna Damage Response, Xi Chen, Yong Zhao, Guo-Min Li, Lin Guo

Toxicology and Cancer Biology Faculty Publications

BACKGROUND: Mediating DNA damage-induced apoptosis is an important genome-maintenance function of the mismatch repair (MMR) system. Defects in MMR not only cause carcinogenesis, but also render cancer cells highly resistant to chemotherapeutics, including alkylating agents. To understand the mechanisms of MMR-mediated apoptosis and MMR-deficiency-caused drug resistance, we analyze a model alkylating agent (N-methyl-N’-nitro-N-nitrosoguanidine, MNNG)-induced changes in protein phosphorylation and abundance in two cell lines, the MMR-proficient TK6 and its derivative MMR-deficient MT1.

RESULTS: Under an experimental condition that MNNG-induced apoptosis was only observed in MutSα-proficient (TK6), but not in MutSα-deficient (MT1) cells, quantitative analysis …

Protection Of Dietary Polyphenols Against Oral Cancer, Yijian Ding, Hua Yao, Yanan Yao, Leonard Yenwong Fai, Zhuo Zhang

Toxicology and Cancer Biology Faculty Publications

Oral cancer represents a health burden worldwide with approximate 275,000 new cases diagnosed annually. Its poor prognosis is due to local tumor invasion and frequent lymph node metastasis. Better understanding and development of novel treatments and chemo-preventive approaches for the preventive and therapeutic intervention of this type of cancer are necessary. Recent development of dietary polyphenols as cancer preventives and therapeutic agents is of great interest due to their antioxidant and anti-carcinogenic activities. Polyphenols may inhibit carcinogenesis in the stage of initiation, promotion, or progression. In particular, dietary polyphenols decrease incidence of carcinomas and exert protection against oral cancer by …

Uv Radiation And The Skin, John A. D'Orazio, Stuart G. Jarrett, Alexandra Amaro-Ortiz, Timothy Scott

Toxicology and Cancer Biology Faculty Publications

UV radiation (UV) is classified as a "complete carcinogen" because it is both a mutagen and a non-specific damaging agent and has properties of both a tumor initiator and a tumor promoter. In environmental abundance, UV is the most important modifiable risk factor for skin cancer and many other environmentally-influenced skin disorders. However, UV also benefits human health by mediating natural synthesis of vitamin D and endorphins in the skin, therefore UV has complex and mixed effects on human health. Nonetheless, excessive exposure to UV carries profound health risks, including atrophy, pigmentary changes, wrinkling and malignancy. UV is epidemiologically and …

Loss Of Fbp1 By Snail-Mediated Repression Provides Metabolic Advantages In Basal-Like Breast Cancer, Chenfang Dong, Tingting Yuan, Yadi Wu, Yifan Wang, Teresa W-M Fan, Sumitra Miriyala, Yiwei Lin, Jun Yao, Jian Shi, Tiebang Kang, Pawel Lorkiewicz, Daret St. Clair, Mien-Chie Hung, B. Mark Evers, Binhua P. Zhou

Toxicology and Cancer Biology Faculty Publications

The epithelial-mesenchymal transition (EMT) enhances cancer invasiveness and confers tumor cells with cancer stem cell (CSC)-like characteristics. We show that the Snail-G9a-Dnmt1 complex, which is critical for E-cadherin promoter silencing, is also required for the promoter methylation of fructose-1,6-biphosphatase (FBP1) in basal-like breast cancer (BLBC). Loss of FBP1 induces glycolysis and results in increased glucose uptake, macromolecule biosynthesis, formation of tetrameric PKM2, and maintenance of ATP production under hypoxia. Loss of FBP1 also inhibits oxygen consumption and reactive oxygen species production by suppressing mitochondrial complex I activity; this metabolic reprogramming results in an increased CSC-like property and tumorigenicity by enhancing …

Luteolin Inhibits Human Prostate Tumor Growth By Suppressing Vascular Endothelial Growth Factor Receptor 2-Mediated Angiogenesis, Poyil Pratheeshkumar, Young-Ok Son, Amit Budhraja, Xin Wang, Songze Ding, Lei Wang, Andrew Hitron, Jeong-Chae Lee, Donghern Kim, Sasidharan Padmaja Divya, Gang Chen, Zhuo Zhang, Jia Luo, Xianglin Shi

Toxicology and Cancer Biology Faculty Publications

Angiogenesis, the formation of new blood vessels from pre-existing vascular beds, is essential for tumor growth, invasion, and metastasis. Luteolin is a common dietary flavonoid found in fruits and vegetables. We studied the antiangiogenic activity of luteolin using in vitro, ex vivo, and in vivo models. In vitro studies using rat aortic ring assay showed that luteolin at non-toxic concentrations significantly inhibited microvessel sprouting and proliferation, migration, invasion and tube formation of endothelial cells, which are key events in the process of angiogenesis. Luteolin also inhibited ex vivo angiogenesis as revealed by chicken egg chorioallantoic membrane assay (CAM) …

Nadph Oxidase 4 Mediates Insulin-Stimulated Hif-1Α And Vegf Expression, And Angiogenesis In Vitro, Dan Meng, Aihong Mei, Junxu Liu, Xueling Kang, Xianglin Shi, Ruizhe Qian, Sifeng Chen

Toxicology and Cancer Biology Faculty Publications

Acute intensive insulin therapy causes a transient worsening of diabetic retinopathy in type 1 diabetes patients and is related to VEGF expression. Reactive oxygen species (ROS) have been shown to be involved in HIF-1α and VEGF expression induced by insulin, but the role of specific ROS sources has not been fully elucidated. In this study we examined the role of NADPH oxidase subunit 4 (Nox4) in insulin-stimulated HIF-1α and VEGF expression, and angiogenic responses in human microvascular endothelial cells (HMVECs). Here we demonstrate that knockdown of Nox4 by siRNA reduced insulin-stimulated ROS generation, the tyrosine phosphorylation of IR-β and IRS-1, …

Quercetin Inhibits Angiogenesis Mediated Human Prostate Tumor Growth By Targeting Vegfr- 2 Regulated Akt/Mtor/P70s6k Signaling Pathways, Poyil Pratheeshkumar, Amit Budhraja, Young-Ok Son, Xin Wang, Zhuo Zhang, Songze Ding, Lei Wang, Andrew Hitron, Jeong-Chae Lee, Mei Xu, Gang Chen, Jia Luo, Xianglin Shi

Toxicology and Cancer Biology Faculty Publications

Angiogenesis is a crucial step in the growth and metastasis of cancers, since it enables the growing tumor to receive oxygen and nutrients. Cancer prevention using natural products has become an integral part of cancer control. We studied the antiangiogenic activity of quercetin using ex vivo, in vivo and in vitro models. Rat aortic ring assay showed that quercetin at non-toxic concentrations significantly inhibited microvessel sprouting and exhibited a significant inhibition in the proliferation, migration, invasion and tube formation of endothelial cells, which are key events in the process of angiogenesis. Most importantly, quercetin treatment inhibited ex vivo angiogenesis …

Inverse Relationship Between Psa And Il-8 In Prostate Cancer: An Insight Into A Nf-Κb-Mediated Mechanism, Yong Xu, Daret K. St. Clair, Fang Fang, William H. St. Clair

Toxicology and Cancer Biology Faculty Publications

Background: Prostate specific antigen (PSA) is traditionally used as an indicator for the presence of prostate cancer (PCa) and radiotherapy is generally used to treat inoperable and locally advanced PCa. However, how cellular PSA level is associated with sensitivity of PCa to radiotherapy is unknown. The previous finding that the RelB-based NF-κB alternative pathway differentially regulates PSA and interleukin-8 (IL-8) in aggressive PCa has directed our attention to the role of RelB in the response of PCa to radiotherapy.

Methodology/Principal Findings: RelB and its targets PSA and IL-8 in PCa cells were manipulated by ectopic expression in PCa …

Manganese Superoxide Dismutase: Guardian Of The Powerhouse, Aaron K. Holley, Vasudevan Bakthavatchalu, Joyce M. Velez-Roman, Daret K. St. Clair

Toxicology and Cancer Biology Faculty Publications

The mitochondrion is vital for many metabolic pathways in the cell, contributing all or important constituent enzymes for diverse functions such as β-oxidation of fatty acids, the urea cycle, the citric acid cycle, and ATP synthesis. The mitochondrion is also a major site of reactive oxygen species (ROS) production in the cell. Aberrant production of mitochondrial ROS can have dramatic effects on cellular function, in part, due to oxidative modification of key metabolic proteins localized in the mitochondrion. The cell is equipped with myriad antioxidant enzyme systems to combat deleterious ROS production in mitochondria, with the mitochondrial antioxidant enzyme manganese …

Phenethyl Isothiocyanate Exhibits Antileukemic Activity In Vitro And In Vivo By Inactivation Of Akt And Activation Of Jnk Pathways, N. Gao, Amit Budhraja, S. Cheng, E.-H. Liu, J. Chen, Z. Yang, D. Chen, Zhuo Zhang, Xianglin Shi

Toxicology and Cancer Biology Faculty Publications

Effects of phenethyl isothiocyanate (PEITC) have been investigated in human leukemia cells (U937, Jurkat, and HL-60) as well as in primary human acute myeloid leukemia (AML) cells in relation to apoptosis and cell signaling events. Exposure of cells to PEITC resulted in pronounced increase in the activation of caspase-3, -8, -9, cleavage/degradation of PARP, and apoptosis in dose- and time-dependent manners. These events were accompanied by the caspase-independent downregulation of Mcl-1, inactivation of Akt, as well as activation of Jun N-terminal kinase (JNK). Inhibition of PI3K/Akt by LY294002 significantly enhanced PEITC-induced apoptosis. Conversely, enforced activation of Akt by a constitutively …

P53 Regulates Oxidative Stress-Mediated Retrograde Signaling: A Novel Mechanism For Chemotherapy-Induced Cardiac Injury, Joyce M. Velez, Sumitra Miriyala, Ramaneeya Nithipongvanitch, Teresa Noel, Chotiros D. Plabplueng, Terry Oberley, Paiboon Jungsuwadee, Holly Van Remmen, Mary Vore, Daret K. St Clair

Toxicology and Cancer Biology Faculty Publications

The side effects of cancer therapy on normal tissues limit the success of therapy. Generation of reactive oxygen species (ROS) has been implicated for numerous chemotherapeutic agents including doxorubicin (DOX), a potent cancer chemotherapeutic drug. The production of ROS by DOX has been linked to DNA damage, nuclear translocation of p53, and mitochondrial injury; however, the causal relationship and molecular mechanisms underlying these events are unknown. The present study used wild-type (WT) and p53 homozygous knock-out (p53(-/-)) mice to investigate the role of p53 in the crosstalk between mitochondria and nucleus. Injecting mice with DOX (20 mg/kg) causes oxidative stress …

The Role Of Xpg In Processing (Cag)N/(Ctg)N Dna Hairpins, Caixia Hou, Tianyi Zhang, Lei Tian, Jian Huang, Liya Gu, Guo-Min Li

Toxicology and Cancer Biology Faculty Publications

BACKGROUND: During DNA replication or repair, disease-associated (CAG)n/(CTG)n expansion can result from formation of hairpin structures in the repeat tract of the newly synthesized or nicked DNA strand. Recent studies identified a nick-directed (CAG)n/(CTG)n hairpin repair (HPR) system that removes (CAG)n/(CTG)n hairpins from human cells via endonucleolytic incisions. Because the process is highly similar to the mechanism by which XPG and XPF endonucleases remove bulky DNA lesions during nucleotide excision repair, we assessed the potential role of XPG in conducting (CAG)n/(CTG)n HPR.

RESULTS: To determine if the XPG endonuclease is involved in (CAG)n/(CTG)n hairpin removal, two XPG-deficient cell lines (GM16024 …

Mir-17* Suppresses Tumorigenicity Of Prostate Cancer By Inhibiting Mitochondrial Antioxidant Enzymes, Yong Xu, Fang Fang, Jiayou Zhang, Sajni Josson, William H. St. Clair, Daret K. St. Clair

Toxicology and Cancer Biology Faculty Publications

Aberrant micro RNA (miRNA) expression has been implicated in the pathogenesis of cancer. Recent studies have shown that the miR-17-92 cluster is overexpressed in many types of cancer. The oncogenic function of mature miRNAs encoded by the miR-17-92 cluster has been identified from the 5' arm of six precursors. However, the function of the miRNAs produced from the 3' arm of these precursors remains unknown. The present study demonstrates that miR-17* is able to suppress critical primary mitochondrial antioxidant enzymes, such as manganese superoxide dismutase (MnSOD), glutathione peroxidase-2 (GPX2) and thioredoxin reductase-2 (TrxR2). Transfection of miR-17* into prostate cancer PC-3 …

The Catalytic Function Of The Rev1 Dcmp Transferase Is Required In A Lesion-Specific Manner For Translesion Synthesis And Base Damage-Induced Mutagenesis, Ying Zhou, Jillian Wang, Yanbin Zhang, Zhigang Wang

Toxicology and Cancer Biology Faculty Publications

The Rev1-Polζ pathway is believed to be the major mechanism of translesion DNA synthesis and base damage-induced mutagenesis in eukaryotes. While it is widely believed that Rev1 plays a non-catalytic function in translesion synthesis, the role of its dCMP transferase activity remains uncertain. To determine the relevance of its catalytic function in translesion synthesis, we separated the Rev1 dCMP transferase activity from its non-catalytic function in yeast. This was achieved by mutating two conserved amino acid residues in the catalytic domain of Rev1, i.e. D467A/E468A, where its catalytic function was abolished but its non-catalytic function remained intact. In this mutant …

Acetylation Of Wrn Protein Regulates Its Stability By Inhibiting Ubiquitination, Kai Li, Rui Wang, Enerlyn Lozada, Wei Fan, David K. Orren, Jianyuan Luo

Toxicology and Cancer Biology Faculty Publications

BACKGROUND: WRN is a multi-functional protein involving DNA replication, recombination and repair. WRN acetylation has been demonstrated playing an important role in response to DNA damage. We previously found that WRN acetylation can regulate its enzymatic activities and nuclear distribution.

METHODOLOGY/PRINCIPAL FINDING: Here, we investigated the factors involved in WRN acetylation and found that CBP and p300 are the only major acetyltransferases for WRN acetylation. We further identified 6 lysine residues in WRN that are subject to acetylation. Interestingly, WRN acetylation can increase its protein stability. SIRT1-mediated deacetylation of WRN reverses this effect. CBP dramatically increases the half-life of wild …

Jnk1 Activation Predicts The Prognostic Outcome Of The Human Hepatocellular Carcinoma, Qingshan Chang, Jianguo Chen, Kevin J. Beezhold, Vince Castranova, Xianglin Shi, Fei Chen

Toxicology and Cancer Biology Faculty Publications

BACKGROUND: Hepatocellular carcinoma (HCC) is one of the most common cancers worldwide with an extremely poor prognosis. The classification of HCC based on the molecular signature is not well-established.

RESULTS: In the present study, we reported HCC signature genes based on the JNK1 activation status in 31 HCC specimens relative to the matched distal noncancerous liver tissue from 31 patients. The HCCs with high JNK1 (H-JNK1) and low JNK1 (L-JNK1) were sub-grouped. Two different signature gene sets for both H-JNK1 and L-JNK1 HCC were identified through gene expression profiling. A striking overlap of signature genes was observed between the H-JNK1 …

Metallic Nickel Nano- And Fine Particles Induce Jb6 Cell Apoptosis Through A Caspase-8/Aif Mediated Cytochrome C-Independent Pathway, Jinshun Zhao, Linda Bowman, Xingdong Zhang, Xianglin Shi, Binghua Jiang, Vincent Castranova, Min Ding

Toxicology and Cancer Biology Faculty Publications

BACKGROUND: Carcinogenicity of nickel compounds has been well documented. However, the carcinogenic effect of metallic nickel is still unclear. The present study investigates metallic nickel nano- and fine particle-induced apoptosis and the signal pathways involved in this process in JB6 cells. The data obtained from this study will be of benefit for elucidating the pathological and carcinogenic potential of metallic nickel particles.

RESULTS: Using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, we found that metallic nickel nanoparticles exhibited higher cytotoxicity than fine particles. Both metallic nickel nano- and fine particles induced JB6 cell apoptosis. Metallic nickel nanoparticles produced higher apoptotic induction than fine …

Dna Instability In Replicating Huntington's Disease Lymphoblasts, Milena Cannella, Vittorio Maglione, Tiziana Martino, Giuseppe Ragona, Luigi Frati, Guo-Min Li, Ferdinando Squitieri

Toxicology and Cancer Biology Faculty Publications

BACKGROUND: The expanded CAG repeat in the Huntington's disease (HD) gene may display tissue-specific variability (e.g. triplet mosaicism) in repeat length, the longest mutations involving mitotic (germ and glial cells) and postmitotic (neurons) cells. What contributes to the triplet mutability underlying the development of HD nevertheless remains unknown. We investigated whether, besides the increased DNA instability documented in postmitotic neurons, possible environmental and genetic mechanisms, related to cell replication, may concur to determine CAG repeat mutability. To test this hypothesis we used, as a model, cultured HD patients' lymphoblasts with various CAG repeat lengths.

RESULTS: Although most lymphoblastoid cell lines …

Suppression Of Peroxisomal Enzyme Activities And Cytochrome P450 4a Isozyme Expression By Congeneric Polybrominated And Polychlorinated Biphenyls, Larry W. Robertson, Isabelle Berberian, Tim Borges, Li-Chuan Chen, Ching K. Chow, Howard P. Glauert, Johannes G. Filser, Helmut Thomas

Toxicology and Cancer Biology Faculty Publications

The purpose of this study was to determine the effects of PCBs and PBBs on peroxisome proliferator-activated receptor-alpha-(PPARalpha-) associated enzyme activities or protein levels. Male Sprague-Dawley rats were administered a single IP injection (150 mu mol/kg) of either 3,3',4,4'-tetrabromobiphenyl, 3,3',4,4'-tetrachlorobiphenyl, 3,3',5,5'-tetrabromobiphenyl, 2',3,3',4,5-pentachlorobiphenyl, 3,3',4,4',5-pentachlorobiphenyl, 2,2',3,3',5,5'-hexachlorobiphenyl, or 3,3',4,4',5,5'-hexabromobiphenyl in corn oil (10 ml/kg). One week later, the activities of catalase, peroxisomal fatty acyl-CoA oxidase, and peroxisomal beta-oxidation as well as cytochrome P450 4A (CYP4A) protein content were determined in subcellular liver fractions. None of the peroxisomal enzyme activities were significantly increased by any of the halogenated biphenyl congeners tested. Except for minor …

Replication Fork Regression In Vitro By The Werner Syndrome Protein (Wrn): Holliday Junction Formation, The Effect Of Leading Arm Structure And A Potential Role For Wrn Exonuclease Activity, Amrita Machwe, Liren Xiao, Robert G Lloyd, Edward Bolt, David K. Orren

Toxicology and Cancer Biology Faculty Publications

The premature aging and cancer-prone disease Werner syndrome stems from loss of WRN protein function. WRN deficiency causes replication abnormalities, sensitivity to certain genotoxic agents, genomic instability and early replicative senescence in primary fibroblasts. As a RecQ helicase family member, WRN is a DNA-dependent ATPase and unwinding enzyme, but also possesses strand annealing and exonuclease activities. RecQ helicases are postulated to participate in pathways responding to replication blockage, pathways possibly initiated by fork regression. In this study, a series of model replication fork substrates were used to examine the fork regression capability of WRN. Our results demonstrate that WRN catalyzes …

Identification And Characterization Of Ogg1 Mutations In Patients With Alzheimer's Disease, Guogen Mao, Xiaoyu Pan, Beibei Zhu, Yanbin Zhang, Fenghua Yuan, Jian Huang, Mark A. Lovell, Maxwell P. Lee, William R. Markesbery, Guo-Min Li, Liya Gu

Toxicology and Cancer Biology Faculty Publications

Patients with Alzheimer's disease (AD) exhibit higher levels of 8-oxo-guanine (8-oxoG) DNA lesions in their brain, suggesting a reduced or defective 8-oxoG repair. To test this hypothesis, this study investigated 14 AD patients and 10 age-matched controls for mutations of the major 8-oxoG removal gene OGG1. Whereas no alterations were detected in any control samples, four AD patients exhibited mutations in OGG1, two carried a common single base (C₇₉₆) deletion that alters the carboxyl terminal sequence of OGG1, and the other two had nucleotide alterations leading to single amino acid substitutions. In vitro biochemical assays revealed …

Length-Dependent Degradation Of Single-Stranded 3' Ends By The Werner Syndrome Protein (Wrn): Implications For Spatial Orientation And Coordinated 3' To 5' Movement Of Its Atpase/Helicase And Exonuclease Domains, Amrita Machwe, Liren Xiao, David K. Orren

Toxicology and Cancer Biology Faculty Publications

BACKGROUND: The cancer-prone and accelerated aging disease Werner syndrome is caused by loss of function of the WRN gene product that possesses ATPase, 3' to 5' helicase and 3' to 5' exonuclease activities. Although WRN has been most prominently suggested to function in telomere maintenance, resolution of replication blockage and/or recombinational repair, its exact role in DNA metabolism remains unclear. WRN is the only human RecQ family member to possess both helicase and exonuclease activity, but the mechanistic relationship between these activities is unknown. In this study, model single-stranded and 3' overhang DNA substrates of varying length and structure were …

Competition Between The Dna Unwinding And Strand Pairing Activities Of The Werner And Bloom Syndrome Proteins, Amrita Machwe, Enerlyn M. Lozada, Liren Xiao, David K. Orren

Toxicology and Cancer Biology Faculty Publications

BACKGROUND: The premature aging and cancer-prone Werner and Bloom syndromes are caused by defects in the RecQ helicase enzymes WRN and BLM, respectively. Recently, both WRN and BLM (as well as several other RecQ members) have been shown to possess a strand annealing activity in addition to the requisite DNA unwinding activity. Since an annealing function would appear to directly oppose the action of a helicase, we have examined in this study the dynamic equilibrium between unwinding and annealing mediated by either WRN or BLM.

RESULTS: Our investigation into the competition between annealing and unwinding demonstrates that, under standard reaction …

Regulation Of The Rat Liver Sodium-Dependent Bile Acid Cotransporter Gene By Prolactin. Mediation Of Transcriptional Activation By Stat5, Tanmoy C. Ganguly, Michelle L. O'Brien, Saul J. Karpen, James F. Hyde, Fredrick J. Suchy, Mary Vore

Toxicology and Cancer Biology Faculty Publications

The intracellular mechanism(s) underlying the upregulation of the hepatic Na+/taurocholate cotransporting polypeptide (ntcp) by prolactin (PRL) are unknown. In this report, we demonstrate a time-dependent increase in nuclear translocation of phosphorylated liver Stat5 (a member of the ignal ransducers and ctivators of ranscription family) that correlated with suckling-induced increases in serum PRL levels. In electrophoretic mobility gel shift assays, nuclear Stat5 exhibited specific DNA-binding ability towards IFN-gamma-activated sequence (GAS)-like elements (GLEs; 5'TTC/A-PyNPu-G/TAA-3') located in the -937 to -904 bp region of the ntcp promoter. Transient cotransfections in HepG2 cells revealed that PRL inducibility (2.5-3-fold) required coexpression of the long form …

The Protective Role Of Manganese Superoxide Dismutase Against Adriamycin-Induced Acute Cardiac Toxicity In Transgenic Mice, Hsiu-Chuan Yen, Terry D. Oberley, Satit Vichitbandha, Ye-Shih Ho, Daret K. St. Clair

Toxicology and Cancer Biology Faculty Publications

Adriamycin (ADR) is a potent anticancer drug known to cause severe cardiac toxicity. Although ADR generates free radicals, the role of free radicals in the development of cardiac toxicity and the intracellular target for ADR-induced cardiac toxicity are still not well understood. We produced three transgenic mice lines expressing increased levels of human manganese superoxide dismutase (MnSOD), a mitochondrial enzyme, as an animal model to investigate the role of ADR-mediated free radical generation in mitochondria. The human MnSOD was expressed, functionally active, and properly transported into mitochondria in the heart of transgenic mice. The levels of copper-zinc SOD, catalase, and …