Kathleen Forrester

P53 modulation of TFIIH-associated nucleotide excision repair activity

p53 has pleiotropic functions including control of genomic plasticity and integrity. Here we report that p53 can bind to several transcription factor IIH–associated factors, including transcription–repair factors, XPD (Rad3) and XPB, as well as CSB involved in strand–specific DNA repair, via its C–terminal domain. We also found that wild–type, but not Arg273His mutant p53 inhibits XPD (Rad3) and XPB DNA helicase activities. Moreover, repair of UV–induced dimers is slower in Li–Fraumeni syndrome cells (heterozygote p53 mutant) than in normal human cells. Our findings indicate that p53 may play a direct role in modulating nucleotide excision repair pathways.

p53-Induced Up-Regulation of MnSOD and GPx but not Catalase Increases Oxidative Stress and Apoptosis

p53-mediated apoptosis may involve the induction of redox-controlling genes, resulting in the production of reactive oxygen species. Microarray expression analysis of doxorubicin exposed, related human lymphoblasts, p53 wild-type (WT) Tk6, and p53 mutant WTK1 identified the p53-dependent up-regulation of manganese superoxide dismutase (MnSOD) and glutathione peroxidase 1 (GPx). Consensus p53 binding sequences were identified in human MnSOD and GPx promoter regions. A 3-fold increase in the MnSOD promoter activity was observed after the induction of p53 in Li-Fraumeni syndrome (LFS) fibroblast, TR9-7, expressing p53 under the control of a tetracycline-regulated promoter. An increased protein expression of endogenous MnSOD and GPx also positively correlated with the level of p53 induction in TR9-7 cells. However, catalase (CAT) protein expression remained unaltered after p53 induction. We also examined the expression of MnSOD, GPx, and CAT in a panel of normal or LFS fibroblasts, containing either WT or mutant p53. We found increased MnSOD enzymatic activity, MnSOD mRNA expression, and MnSOD and GPx protein in LFS fibroblasts carrying a WT p53 allele when compared with homozygous mutant p53 isogenic cells. The CAT protein level was unchanged in these cells. We observed both the release of cytochrome C and Ca2+ from the mitochondria into the cytoplasm and an increased frequency of apoptotic cells after p53 induction in the TR9-7 cells that coincided with an increased expression of MnSOD and GPx, and the level of reactive oxygen species. The increase in apoptosis was reduced by the antioxidant N-acetylcysteine. These results identify a novel mechanism of p53-dependent apoptosis in which p53-mediated up-regulation of MnSOD and GPx, but not CAT, produces an imbalance in antioxidant enzymes and oxidative stress.

Abrogation of p53-induced Apoptosis by the Hepatitis B Virus X Gene

The p53 tumor suppressor gene product is a transcriptional transactivator and a potent apoptotic inducer. The fact that many of the DNA tumor virus oncoproteins bind to p53 and affect these p53 functions indicates that this interaction is an important step in oncogenic transformation. We and others have recently demonstrated that the hepatitis B virus oncoprotein, HBx, can form a complex with p53 and inhibit its DNA consensus sequence binding and transcriptional transactivator activity. Using a microinjection technique, we report here that HBx efficiently blocks p53-mediated apoptosis and describe the results of studies exploring two possible mechanisms of HBx action. First, inhibition of apoptosis may be a consequence of the failure of p53, in the presence of HBx, to upregulate genes, such as p21WAF1, Bax, or Fas, that are involved in the apoptotic pathway. Data consistent with this hypothesis include HBx reduction of p53-mediated p21WAF1 expression. Alternatively, HBx could affect p53 binding to the TFIIH transcription-nucleotide excision repair complex as HBx binds to the COOH terminus of p53 and inhibits its binding to XPB or XPD. Binding of p53 to these constituents of the core TFIIH is a process that may be involved in apoptosis. Because the HBx gene is frequently integrated into the genome of hepatocellular carcinoma cells, inhibition of p53-mediated apoptosis by HBx may provide a clonal selective advantage for hepatocytes expressing this integrated viral gene during the early stages of human liver carcinogenesis.Hepatocellular carcinoma (HCC) is one of the most prevalent malignant diseases worldwide and has become a leading cause for cancer-related deaths in adults from Asia and sub-Saharan Africa (1). The DNA tumor virus hepatitis B virus (HBV) has been implicated to play a major causative role in the development of HCC in man (2-4). The HBx gene, the smallest viral openreading frame that may be essential for the viral life cycle (5,6), largely contributes the oncogenecity of HBV. The selective retention and expression of the HBx gene during acute and chronic hepatitis as well as in a great majority of HCCs may constitute an important step during HCC development (7,8). The oncogenic potential of the HBx gene has been experimentally demonstrated in a transgenic mice model (9) and in cell culture systems (10,11). HBx alone can induce HCC in certain transgenic mice (9) or can increase susceptibility to chemical carcinogens (12) and accelerate c-myc-induced HCC (13). Consequently, as an oncoprotein, HBx has been reported to disregulate cell-cycle transition (14,15) to potentially target certain proteases and proteasome (16-18), to interact with DNA repair factors (19,20), or to interact with the p53 tumor suppressor gene product (21-24).

Detection of c-K-ras mutations in fine needle aspirates from human pancreatic adenocarcinomas

This work was supported by Community of Madrid (Grupo Estrategico 2000-2003), NIH, grant R01CA77575, and SAF 2001-2245.The transition step from the p3-dAMP initiation complex to the first elongated products, p3-(dAMP)2 and p3-(dAMP)3, requires a dATP concentration higher than that needed for the initiation reaction or for the further elongation of the p3-(dAMP)3 complex. The elongation in phi 29 DNA-protein p3 replication in vitro was strongly inhibited by salt. Under inhibitory salt concentration, the viral protein p6 greatly stimulated phi 29 DNA-protein p3 replication. The effect of protein p6 was not on the rate of elongation but on the amount of elongated product, stimulating the transition from initiation to formation of the first elongation products.Trabajo presentado en 44th Annual Meeting Society for Neuroscience, celebrado en Washington, DC (USA) del 15 al 19 de noviembre de 2014Recent studies have demonstrated that cytochrome c plays an important role in cell death. In the present study, we report that teniposide and various other chemotherapeutic agents induced a dose-dependent increase in the expression of the mitochondrial respiratory chain proteins cytochrome c, subunits I and IV of cytochrome c oxidase, and the free radical scavenging enzyme manganous superoxide dismutase. The teniposide-induced increase of cytochrome c was inhibited by cycloheximide, indicating new protein synthesis. Elevated cytochrome c levels were associated with enhanced cytochrome c oxidase-dependent oxygen uptake using TMPD/ascorbate as the electron donor, suggesting that the newly synthesized proteins were functional. Cytochrome c was released into the cytoplasm only after maximal levels had been reached in the mitochondria, but there was no concomitant decrease in mitochondrial membrane potential or caspase activation. Our results suggest that the increase in mitochondrial protein expression may play a role in the early cellular defense against anticancer drugs.Supported by Grant GM-08041 from the National Institutes of Health, United States Public Health Service.The results presented in this paper indicate that the phi 29 DNA polymerase is the only enzyme required for efficient synthesis of full length phi 29 DNA with the phi 29 terminal protein, the initiation primer, as the only additional protein requirement. Analysis of phi 29 DNA polymerase activity in various in vitro DNA replication systems indicates that two main reasons are responsible for the efficiency of this minimal system: 1) the phi 29 DNA polymerase is highly processive in the absence of any accessory protein; 2) the polymerase itself is able to produce strand displacement coupled to the polymerization process. Using primed M13 DNA as template, the phi 29 DNA polymerase is able to synthesize DNA chains greater than 70 kilobase pairs. Furthermore, conditions that increase the stability of secondary structure in the template do not affect the processivity and strand displacement ability of the enzyme. Thus, the catalytic properties of the phi 29 DNA polymerase are appropriate for a phi 29 DNA replication mechanism involving two replication origins, strand displacement and continuous synthesis of both strands. The enzymology of phi 29 DNA replication would support a symmetrical model of DNA replication.Aided by grants from the National Institutes of Health U.S. Public Health Service, and E. I. Du Pont de Neumours and Company, Inc.This work was supported in part by NRSA, National Institutes of Health Grants NS09463 and NS32501 and from National Science Foundation Grant 9310965.We have recently developed a new method to detect and characterize single base substitutions in transcribed genes which is based on the ability of RNAse A to recognize and cleave single base mismatches in RNA:RNA heteroduplexes. The RNAse A misrnatch cleavage assay was applied to screen human colon carcinoma cell lines and primary tumors for the presence of mutant e-X-ras oncogenes. We have determined that the mutant e-X-ras allele is overexpressed and amplified relative to the normal in the SX-CO-l human colon carcinoma cell lineo The oncogene mutation has been characterized by this method as a glycine to valine substitution at codon 12 of the e-X-ras gene. This result was confirmed by cloning and sequencing. We have previously reported that about 40% of primary human colon tumors contain e-X-ras genes mutant at codon 12 (Forrester et al, Nature 327: 298, 1987). We report here the characterization by molecular cloning and sequencing of the mutation in the e-X-ras oneogene from two of these tumors (tumors 3 and 28). We also describe the histopathologieal eharaeterization of these two tumors and demonstrate, by Southern blot hybridization of NIH3T3 transformants, the simultaneous presenee of mutant e-X-ras and N-ras oncogenes in villous adenoma 28. Our results provide evidence for the frequent assoeiation of ras somatie mutational aetivation in the early stages of tumor development in this common type of human eaneer.Aided by Grants AM-01845, AM-08953, and l-Sol-FR-05099 from the National Institutes o f Health, United States Public Health Service, and E. I. Du Pont de Nemours and Company, Inc. A preliminary report o f this work was presented at the Second Meeting o f the Federation o f European Biochemical Societies (symposium on “Ribonucleic Acid-Structure and Function”), Vienna, April 21 to 24, 1965.1 pagina.-- Trabajo presentado al: 4th International Meeting on Apicomplexa in Farm Animals. (Madrid, Spain. 11-14 October ,2017).Supported by Grant GM-08041 from the National Institutes of Health, United States Public Health Service.Resumen del trabajo presentado al XXXIII Congreso de la Sociedad Espanola de Bioquimica y Biologia Molecular celebrado en Cordoba del 14 al 17 de septiembre de 2010.This article describes the expression pattern and functional analysis of Lazarillo, a novel cell surface glycoprotein expressed in the embryonic grasshopper nervous system, and a member of the lipocalin family. Lazarillo is expressed by a subset of neuroblasts, ganglion mother cells and neurons of the central nervous system, by all sensory neurons of the peripheral nervous system, and by a subset of neurons of the enteric nervous system. It is also present in a few non neuronal cells associated mainly with the excretory system. A monoclonal antibody raised against Lazarillo perturbs the extent and direction of growth of identified commissural pioneer neurons. We propose that Lazarillo is the receptor for a midline morphogen involved in the outgrowth and guidance of these neurons.Poster presentado al Annual Biomedical Research Conference for Minority Students celebrado en California (US) del 7 al 10 de noviembre de 2012.The phage phi 29 regulatory protein p4 activates the late promoter A3 by stabilizing the binding of Bacillus subtilis RNA polymerase (RNAP) as a closed complex. Interaction between the two proteins occurs through amino acid Arg120 in protein p4 and the C-terminal domain of the RNAP alpha subunit (alpha-CTD). In addition to its role as activator of the late transcription, protein p4 represses early transcription from the A2b and A2c promoters, that are divergently transcribed. Binding of p4 to its recognition site at the A3 promoter displaces the RNAP from promoter A2b, both by steric hindrance and by the curvature induced upon p4 binding. At the A2c promoter, the RNAP cooperates with p4 binding in such a way that promoter clearance is prevented. Interestingly, amino acid Arg120 in p4 and the alpha-CTD in B. subtilis RNAP are involved in the interactions that lead to transcription repression at promoter A2c. To investigate how this interaction leads to activation at PA3 and to repression at PA2c, mutant promoters were constructed. In the absence of a -35 consensus box for sigma A-RNAP activation was observed, while in its presence repression occurred. The results support the idea that overstabilization of RNAP at the promoter over a threshold level leads to repression.Resumen del poster presentado al XXXIII Congreso de la Sociedad Espanola de Bioquimica y Biologia Molecular celebrado en Cordoba del 14 al 17 de septiembre de 2010.Formalin-fixed paraffin-embedded tissue specimens obtained by fine needle aspiration of pancreatic masses from 47 patients were examined retrospectively for cytology and the presence of mutant c-K-ras oncogenes. Point mutations of c-K-ras in codon 12 were detected by RNA-DNA RNAse A mismatch cleavage after in vitro DNA amplification of the cellular c-K-ras sequences by the polymerase chain reaction. Of the 36 patients with pancreatic adenocarcinoma, mutant c-K-ras oncogenes were detected in 18 of 25 (72%) with malignant cytologies, 2 of 8 (25%) with atypical cytologies, and 0 of 3 with benign aspiration cytologies. The remaining 11 patients without pancreatic adenocarcinomas did not have mutant c-K-ras genes detectable by the assay. The diagnosis of pancreatic adenocarcinoma was based upon clinical follow-up. The presence of mutant c-K-ras oncogenes did not significantly affect survival in the patients studied. Mutant c-K-ras genes were found at the time of initial clinical presentation in the majority of pancreatic adenocarcinomas, suggesting an important role of the mutation in oncogenesis. In conjunction with cytology, our approach represents an application for cancer diagnosis at the molecular genetic level.Calorie restriction (CR) has been shown to decrease reactive oxygen species (ROS) production and retard aging in a variety of species. It has been proposed that alterations in membrane saturation are central to these actions of CR. As a step towards testing this theory, mice were assigned to 4 dietary groups (control and 3 CR groups) and fed AIN-93G diets at 95 % (control) or 60 % (CR) of ad libitum for 8 months. To manipulate membrane composition, the primary dietary fats for the CR groups were soybean oil (also used in the control diet), fish oil or lard. Skeletal muscle mitochondrial lipid composition, proton leak, and H(2)O(2) production were measured. Phospholipid fatty acid composition in CR mice was altered in a manner that reflected the n-3 and n-6 fatty acid profiles of their respective dietary lipid sources. Dietary lipid composition did not alter proton leak kinetics between the CR groups. However, the capacity of mitochondrial complex III to produce ROS was decreased in the CR lard compared to the other CR groups. The results of this study indicate that dietary lipid composition can influence ROS production in muscle mitochondria of CR mice. It remains to be determined if lard or other dietary oils can maximize the CR-induced decreases in ROS production.To investigate the relationship between RNA folding and ribozyme catalysis, we have carried out a detailed kinetic analysis of four structural derivatives of the hairpin ribozyme. Optimal and suboptimal (wild-type) substrate sequences were studied in conjunction with stabilization of helix 4, which supports formation of the catalytic core. Pre-steady-state and steady-state kinetic studies strongly support a model in which each of the ribozyme variants partitions between two major conformations leading to active and inactive ribozymez substrate complexes. Reaction rates for cleavage, ligation, and substrate binding to both ribozyme conformations were determined. Ligation rates (3 min 21 ) were typically 15-fold greater than cleavage rates (0.2 min 21 ), demonstrating that the hairpin ribozyme is an efficient RNA ligase. On the other hand, substrate binding is very rapid (k on 5 4 3 10 8 M 21 min 21 ), and the ribozymez substrate complex is very stable (K D < 25 pM ;k off < 0.01 min 21 ). Stabilization of helix 4 increases the proportion of RNA molecules folded into the active conformation, and enhances substrate association and ligation rates. These effects can be explained by stabilization of the catalytic core of the ribozyme. Rigorous consideration of conformational isomers and their intrinsic kinetic properties was necessary for development of a kinetic scheme for the ribozyme-catalyzed reaction.The human integrin VLA (very late activation antigens)-4 (CD49d/CD29), the leukocyte receptor for both the CS-1 region of plasma fibronectin (Fn) and the vascular cell surface adhesion molecule-1 (VCAM-1), also mediates homotypic aggregation upon triggering with specific anti-VLA-4 monoclonal antibody (mAb). Epitope mapping of this integrin on the human B-cell line Ramos, performed with a wide panel of anti-VLA-4 mAb by both cross-competitive cell binding and protease sensitivity assays, revealed the existence of three topographically distinct epitopes on the alpha 4 chain, referred to as epitopes A-C. By testing this panel of anti-VLA-4 mAb for inhibition of cell binding to both a 38-kDa Fn fragment containing CS-1 and to VCAM-1, as well as for induction and inhibition of VLA-4 mediated homotypic cell adhesion, we have found overlapping but different functional properties associated with each epitope. Anti-alpha 4 mAb recognizing epitope B inhibited cell attachment to both Fn and VCAM-1, whereas mAb against epitope A did not block VCAM-1 binding and only partially inhibited binding to Fn. In contrast, mAb directed to epitope C did not affect cell adhesion to either of the two VLA-4 ligands. All mAb directed to site A, as well as a subgroup of mAb recognizing epitope B (called B2), were able to induce cell aggregation, but this effect was not exerted by mAb specific to site C and by a subgroup against epitope B (called B1). Moreover, although anti-epitope C and anti-epitope B1 mAb did not trigger aggregation, those mAb blocked aggregation induced by anti-epitope A or B2 mAb. In addition, anti-epitope A mAb blocked B2-induced aggregation, and conversely, anti-epitope B2 mAb blocked A-induced aggregation. Further evidence for multiple VLA-4 functions is that anti-Fn and anti-VCAM-1 antibodies inhibited binding to Fn or to VCAM-1, respectively, but did not affect VLA-4-mediated aggregation. In summary, we have demonstrated that there are at least three different VLA-4-mediated adhesion functions, we have defined three distinct VLA-4 epitopes, and we have correlated these epitopes with the different functions of VLA-4.Lazarillo, a protein recognized by the monoclonal antibody 10E6, is expressed by a subset of neurons in the developing nervous system of the grasshopper. It is a glycoprotein of 45x10(3) M(r) with internal disulfide bonds and linked to the extracellular side of the plasma membrane by a glycosylphosphatidylinositol moiety. Peptide sequences obtained from affinity purified adult protein were used to identify an embryonic cDNA clone, and in situ hybridizations confirmed that the distribution of the Lazarillo mRNA paralleled that of the monoclonal antibody labeling on embryos. Sequence analysis defines Lazarillo as a member of the lipocalin family, extracellular carriers of small hydrophobic ligands, and most related to the porphyrin- and retinol-binding lipocalins. Lazarillo is the first example of a lipocalin anchored to the plasma membrane, highly glycosylated, and restricted to a subset of developing neurons.Trabajo presentado al Annual Biomedical Research Conference for Minority Students celebrada en Nashville (US) del 13 al 16 de noviembre de 2013.A cDNA has been isolated from human hippocampus that appears to encode a novel Na(+)-dependent, Cl(-)-independent, neutral amino acid transporter. The putative protein, designated SATT, is 529 amino acids long and exhibits significant amino acid sequence identity (39-44%) with mammalian L-glutamate transporters. Expression of SATT cDNA in HeLa cells induced stereospecific uptake of L-serine, L-alanine, and L-threonine that was not inhibited by excess (3 mM) 2-(methylamino)-isobutyric acid, a specific substrate for the System A amino acid transporter. SATT expression in HeLa cells did not induce the transport of radiolabeled L-cysteine, L-glutamate, or related dicarboxylates. Northern blot hybridization revealed high levels of SATT mRNA in human skeletal muscle, pancreas, and brain, intermediate levels in heart, and low levels in liver, placenta, lung, and kidney. SATT transport characteristics are similar to the Na(+)-dependent neutral amino acid transport activity designated System ASC, but important differences are noted. These include: 1) SATTs apparent low expression in ASC-containing tissues such as liver or placenta; 2) the lack of mutual inhibition between serine and cysteine; and 3) the lack of trans-stimulation. SATT may represent one of multiple activities that exhibit System ASC-like transport characteristics in diverse tissues and cell lines.

Molecular analysis of the cyclin-dependent kinase inhibitor genesp15INK4b/MTS21,p16INK4/MTS1,p18 andpl9 in human cancer cell lines

Cyclin‐dependent kinase‐4 inhibitor genes (INK4) regulate the cell cycle and are candidate tumor‐suppressor genes. To determine if alterations in the coding regions of the pl8 and pl9 genes, which are novel members of the INK4 family and if they correlate with the development of human cancer, 100 human cancer cell lines were analyzed. Two other INK4 gene family members, p15INK4b/MTS2 and pl6INK4/MTS1 genes were also analyzed. Homozygous deletions of the p15INK4b/MTS2 gene were detected in 29 cancer cell lines. Thirty‐five homozygous deletions and 7 intragenic mutations of the pl6INK4/MTS1 gene were also detected in these cell lines. Neither homozygous deletions nor intragenic mutations of the p18 and p19 genes were found except in an ovarian cancer cell line, SKOV3, harboring a single base pair deletion in exon 1 of p19. In p16INK4/MTS1 expression analysis, 5 cell lines with both authentic and alternative spliced pl6INK4/MTS1 mRNA had no detectable pl6INK4/MTS1 protein. These results suggest the hypotheses that either post‐translational modification or enhanced degradation may be responsible for the lack of detection of the pl6INK4/MTS1 protein. Using Western blot analysis, subsets of 26 human cancer cell lines were examined for pl8 expression and 39 cell lines for p19 expression. All of these cell lines expressed the pl8 or pl9 protein, with the exception of SKOV3, which did not express pl9. Therefore, the INK4 gene family may be divided into 2 groups. One group includes p15INK4b/MTS2 and pl6INK4/MTS1 in which genetic and epigenetic alterations might contribute to the development of human cancers. The other group includes p18 and p19, in which somatic mutations are uncommon in many types of human cancer, and their role in human carcinogenesis and cancer progression is uncertain. (This article is a US Government work and, as such, is in the public domain in the United States of America.)

Differential effects of p53 mutants on the growth of human bronchial epithelial cells

We investigated the effects of five different p53 mutants on the growth of primary cultures of normal human bronchial epithelial (NHBE) cells. The five defective viral pZIP‐Neo constructs contained the following mutations at mutational hot‐spots found in human cancers: codons 143ala, 175his, 248trp, 249ser, and 273his. NHBE cells were infected with the p53 mutants, wild‐type p53, or the pZIP‐Neo vector control. The 143ala, 248trp, and 273his mutants, as well as wild‐type p53, decreased the colony‐forming efficiency and inhibited the growth of NHBE cells. The 175his mutant did not significantly change the growth rates. In NHBE cells from three donors, the 249ser mutant conferred a substantial growth advantage to the NHBE cells in a colony–forming–efficiency assay. In NHBE cells isolated from one donor, the 249ser mutant also produced a significant life span extension. These cells grew rapidly through 80 population doublings and entered an apparent “crisis” in passage 14. Karyotypic analyses of one culture at multiple passages revealed aneuploid populations with alterations of chromosomes 5, 11, and 13; quantitative DNA analysis detected aneuploidy in late passages from that culture and two other primary cultures. These data demonstrated that the codon 249ser mutation could provide a growth advantage to bronchial epithelial cells and suggest that this mutant protein can induce genomic instability. Mol. Carcinog. 19:191–203, 1997.