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PubMed2001

Subjective and discriminative stimulus effects of two de-nicotinized cigarettes with different tar yields.

The role of tar yield in the subjective and discriminative stimulus effects of cigarette smoking was examined. Current smokers (n=18) smoked two non-nicotine cigarettes with FTC yields of 0.06 mg nicotine and 12.4 mg (low tar) or 17.9 mg tar (high tar). Physiological measures and visual analog scales were completed over a 30-min period. Dosing order was determined randomly and counterbalanced. After sampling both cigarettes, volunteers smoked a third, test cigarette. Half of the volunteers received the low-tar cigarette and half the high-tar cigarette. Volunteers identified the test cigarette (i.e., A or B) at 5, 30, 60, 300, and 900 s after the first puff. Eight of the eighteen participants correctly identified the test cigarette on 4/5 of trials. No significant changes in visual analog scale scores were found among the non-discriminators. However, among discriminators, the low-tar cigarette produced significant positive effects including good drug effects and stimulation relative to the high-tar cigarette. Relative to the low-tar cigarette, the high-tar cigarette produced negative effects including harshness, heaviness, and intensity of flavor. Average tar yield of these participants' usual cigarettes was 9.75 mg, lower than that of the low-tar cigarette used here, possibly accounting for their greater liking of the low-tar cigarette. No changes in blood pressure or heart rate were observed and both cigarettes produced similar carbon monoxide increases, indicating similar depth of inhalation when smoking each. Results suggest cigarette tar yields may play a role in cigarette smoking preferences. Further research is needed to verify whether preferences are maintained after associations with nicotine delivery are extinguished.

Adult↗
PubMed1997

Inhibition of transcription by the TAR RNA of HIV-1 in a nuclear extract of HeLa cells.

Regulation of transcription of human immunodeficiency virus type-1 (HIV-1) requires specific interaction of Tat protein with the trans-activation response region (TAR). Inhibition of replication of HIV-1 has previously been achieved with a TAR decoy, namely a short RNA oligonucleotide that corresponded to the sequence of the authentic TAR RNA. Since TAR RNA has the potential to interact with cellular factors, we examined the effect of TAR RNA on efficiency of transcription in nuclear of HeLa cell extracts. We performed an in vitro transcription assay in the presence of authentic TAR RNA using a template that was driven by the CMV (cytomegalovirus) early promoter in a HeLa nuclear extract and found, for the first time, that TAR RNA inhibited transcription by approximately 60-70% independently of the Tat-TAR interaction. Furthermore, we evaluated inhibition of transcription by variants of TAR RNA and found that the TAR RNA loop, bases surrounding the loop, the triple base bulge and the 'lower' stem region of TAR RNA were responsible for the inhibition of transcription. Taken together, earlier reports on proteins that bind to TAR RNA and the present results suggest that integrity of TAR RNA is important for efficient binding to cellular transcription factors. As judged from the significant inhibition observed in this study, the TAR decoy might sequester transcription factors and thus it might potentially be able to inhibit transcription of housekeeping genes that are unrelated to Tat function.

Base Sequence↗
PubMed1985

Comparative chemical and biological analysis of coal tar-based therapeutic agents to other coal-derived materials.

In this study, methodologies developed for the analysis of synthetic fuel products were applied to the coal tar fractions isolated from coal tar-based pharmaceutical products. A pharmaceutical stock solution of 20% coal tar in alcohol, a 50% coal tar bath emulsion and a 4.3% coal tar shampoo were studied. The toxicology and chemical composition of the coal tar fractions isolated from these materials were compared with an industrial coal tar and with a direct-liquefaction coal liquid product. The coal tars and coal liquid product were fractionated into chemical classes by alumina column chromatography and individual components were identified and quantitated by high-resolution gas chromatography. The microbial mutagenicity of these materials was measured against S. typhimurium, TA 98. In addition, the industrial coal tar, coal-liquid product, and coal tar isolate from the 20% coal tar in alcohol solution were tested for initiating activity in an initiation/promotion mouse skin painting assay for carcinogenicity. The chemical compositions of the coal tar-based therapeutic agents, the industrial coal tar and direct-liquefaction coal liquid were similar. With the exception of the 50% bath emulsion, the microbial mutagenicity and tumor-initiating activity in mouse skin for those materials tested were also similar.

Animals↗
PubMedDate not supplied

Effectiveness of a new device to retain carcinogenic compounds of tar from mainstream cigarette smoke for the prevention of smoking-associated tumors.

PURPOSE: Effectiveness of a new device inserted within the common cellulose acetate cigarette filter (named hypobaric chamber tar-removing system, HCTRS) to remove tar and its carcinogenic compounds from mainstream cigarette smoke (MCS). METHODS: Eighty HCTRS prototypes were mounted inside the cellulose acetate filter of commercial-brand cigarettes (13 mg tar) and smoked by eighty smoker volunteers. Tar retained by HCTRS prototypes was determined by weighing them before and after smoking. Subsequently, an aliquot (3-5 mg) of the tar retained by twenty randomly chosen HCTRS prototypes was analysed by high-performance liquid chromatography (HPLC) for the detection of polycyclic aromatic hydrocarbons (PAH). RESULTS: The mean value of tar retained was 12.80 mg/HCTRS prototype (S.D. = 5.31), thus showing that this simple device is capable of removing 98.5% of tar present in MCS. Minimal and maximal amounts of retained tar were 4.15 and 31.47 mg/HCTRS prototype, respectively. Moreover, these tar samples contained, although in differing amounts, each of the 16 priority pollutant PAH. A mean value of 259.42 ng/mg of tar (S.E.M. = 44.37) of the 16 main PAH was found in the tar of the 20 HCTRS prototypes examined. These data cogently demonstrate that the use of the HCTRS prototype can effectively eliminate about 100% of tar from MCS, thus reducing the inhalation of PAH (considered the most obvious carcinogenic tar components). CONCLUSIONS: The application of this device could be a suitable tool for effectively improving human health through the prevention of smoking-associated cancer.

Carcinogens↗
PubMed1994

Functional significance of the dinucleotide bulge in stem-loop1 and stem-loop2 of HIV-2 TAR RNA.

Human immunodeficiency virus types 1 and 2 (HIV-1 and HIV-2) encode related proteins called Tat-1 and Tat-2, respectively, that bind directly to the TAR RNA element contained at the 5' ends of viral transcripts and thereby stimulate transcription through an as yet unidentified mechanism. The determinants in the HIV-1 TAR element (TAR-1) that specify binding by the Tat-1 protein have been extensively characterized, while little is known about determinants in the HIV-2 TAR element (TAR-2) that specify binding by the Tat-2 protein. The HIV-2 TAR RNA element (TAR-2) is known to be composed of two stem-loop structures. A dinucleotide bulge is found in each stem of TAR-2 RNA, analogous to the crucial trinucleotide bulge in the single stem-loop of HIV-1 TAR RNA that is the primary binding determinant for binding by the HIV-1 Tat protein. Our results of a nuclease digestion analysis demonstrated that the 5' proximal bulge in TAR-2 is significantly less sensitive to digestion by single-strand specific nucleases than the 3' distal bulge, suggesting that the 5' bulge may be involved in tertiary interaction with other regions of TAR RNA. Deletion of both bulges reduced binding in vitro by the Tat-2 protein and largely abolished transactivation in vivo by Tat-2. Deletion of either bulge alone simplified the pattern of protein/RNA complexes in a gel shift assay, but did not reduce the overall binding affinity of Tat-2. Deletion of the 5' bulge reduced Tat-2 transactivation in vivo to a level approximately 30% that of wild-type TAR-2, while deletion of the 3' bulge had no measurable effect in vivo. Our results suggest that each dinucleotide bulge specifies a Tat-2 binding site, but in the wild-type TAR-2 element the 3' bulge binding site does not appear to be utilized in vivo.

Base Sequence↗
PubMed2001

Trends in sales weighted tar, nicotine, and carbon monoxide yields of UK cigarettes.

BACKGROUND: Reducing tar yields of manufactured cigarettes has been an important plank of government policy on tobacco, but sale weighted yields are not routinely published. METHODS: Tar, nicotine, and carbon monoxide yields measured by the Laboratory of the Government Chemist were combined with cigarette brand market shares from national surveys of smoking behaviour to generate sales weighted yield estimates for the period 1972-99. RESULTS: Sales weighted mean tar yields have declined steadily and in 1999 were 9.6 mg per cigarette, less than half their level in 1972. Over the same period nicotine yields have come down from 1.33 mg to 0.79 mg per cigarette. Carbon monoxide yields have shown smaller declines. At the same time as absolute yields have declined, there have also been changes in tar to nicotine ratios. Smokers in 1999 were exposed to 22% less tar per unit of nicotine than in 1973, and smokers of low tar brands have consistently been exposed to less tar per unit of nicotine than smokers of other brands. CONCLUSIONS: The value of reducing cigarette tar and nicotine yields has been questioned, since the tendency of smokers to compensate for reductions in nicotine delivery undermines the policy. The favourable trends in tar to nicotine ratios suggest that, despite this, there may have been some modest public health benefit. It cannot be assumed that future reductions from present levels would necessarily result in further improvement in tar to nicotine ratios. An explicit focus on the ratio of tar to nicotine may provide a metric of greater relevance for public health than the present emphasis on absolute tar yields.

Carbon Monoxide↗
PubMed1996

Smokers' knowledge and understanding of advertised tar numbers: health policy implications.

OBJECTIVES: This article examines health policy implications of providing smokers with numerical tar yield information in cigarette advertising. METHODS: Results of a national probability telephone survey regarding smokers' knowledge and understanding of numerical tar yields and deliveries are reported. RESULTS: Few smokers knew the tar level of their own cigarettes (the exception being smokers of 1- to 5-mg tar cigarettes), and a majority could not correctly judge the relative tar levels of cigarettes. Smokers were unsure whether switching to lower-tar cigarettes would reduce their personal health risks. Many smokers relied on absolute numbers in making trade-offs between number of cigarettes smoked and their tar levels, thus confusion machine-rated tar-yields with actual amounts ingested. CONCLUSIONS: The wisdom of the present method of providing tar and nicotine numbers in ads and recommendations for modifying the test protocol are now under discussion. This research indicates that these tar numbers and their implications are poorly understood. The paper recommends revisions in tar ratings to make them more useful and a required statement on cigarette packages to more explicitly relate tar levels to major health risks.

Adult↗
PubMed1995

Chronic toxicity of tar from heavy-duty diesel exhaust following intratracheal instillations to the lungs of hamsters.

Chronic toxicity of tar from heavy-duty diesel exhaust (HD tar) was studied in male Syrian golden hamsters which received 15 mg, 7.5 mg or 1.5 mg of HD tar as the total dosages by intratracheal instillations once a week for 15 weeks. As a control group, hamsters were treated with the 0.1 ml of Tween 60: ethanol: phosphate buffer (pH 6.88, 0.25 M) solution (5.8: 8.7: 100 by volume) once a week in the same manner. The survival rate during the instillation period in the group given 15 mg of HD tar, the high-dose group of HD tar, was the lowest, and the effect was dose-dependent. However, the survival rates during the subsequent observation period showed no marked differences among HD tar treated groups. During their total life span, one papilloma in the larynx was seen in the 44 hamsters in the group given 1.5 mg of HD tar, one papilloma in the larynx was appeared in the 59 hamsters in the group given 1.5 mg of HD tar and one lung adenoma was developed in the 58 hamsters in the control group. There were no tumors in the respiratory tract in the group given 7.5 mg of HD tar. Concerning the histopathological findings of the lung, the incidence of alveolar cell or bronchiolar cell hyperplasia in the group given 1.5 mg of HD tar was significantly higher than that in the control group. From these results, although we could not observe any tumorigenicity or carcinogenic effect of HD tar, it would seem that HD tar caused weak but positive damage to the lungs of hamsters.

Animals↗
PubMed1995

Interaction of human immunodeficiency virus type 1 Tat-derived peptides with TAR RNA.

Basic peptides from the carboxy terminus of the human immunodeficiency virus type 1 (HIV-1) Tat protein bind to the stem-loop region of TAR RNA, spanning a trinucleotide bulge, with high affinity and moderate specificity. Previous studies have demonstrated that TAR RNA contains a specific arginine binding pocket. A series of 24 amino acid Tat-derived peptides with one or two arginines has been evaluated as possible structural models of the wild-type peptide in its interaction with TAR RNA, using gel electrophoretic methods and circular dichroism (CD) spectroscopy. Dissociation rate measurements indicate that these peptides form complexes with TAR RNA that are significantly less stable kinetically than the wild-type complex. Through a combination of dissociation and association rate measurements, we estimate that wild-type Tat peptide and TAR RNA interact with a Kd of about 16 pM. Together with competition experiments, these results confirm that band shift gel titration methods significantly underestimate absolute peptide-RNA binding affinities in the subnanomolar range. Through competition experiments with bulge mutants of TAR RNA, we demonstrate that peptides that form longer lived complexes with wild-type TAR RNA also show greater discrimination over TAR RNA bulge mutants. Difference CD spectra show that the Tat-derived peptides do not induce the same changes in TAR RNA as the wild-type peptide. The difference CD spectrum of argininamide bound to TAR RNA is most similar to that of the wild-type peptide-TAR RNA complex, implying that the differences in CD spectra upon complex formation are mostly due to changes in TAR RNA conformation.

Amino Acid Sequence↗
PubMed2000

Inhibition of Tat-mediated transactivation of HIV-1 LTR transcription by polyamide nucleic acid targeted to TAR hairpin element.

Tat, an essential human immunodeficiency virus type 1 protein interacts with the transactivation response element (TAR) and stimulates transcription from the viral long-terminal repeat (LTR). Blockage of Tat-TAR interaction halts viral transcription and hence replication. We have found that polyamide nucleic acid (PNA), targeted to the TAR sequences of viral RNA genome is able to prevent Tat-TAR interaction by efficient sequestration of the TAR. Anti-TAR PNA competes for TAR and prevents Tat-mediated stimulation of HIV-1 LTR transcription in vitro but has no influence on the basal level of transcription in the absence of Tat. Using a reporter gene construct pHIV LTR-CAT and pCMV-Tat in cell culture, we have further shown that anti-TAR PNA is able to block Tat-mediated transactivation of HIV-1 LTR transcription in vivo as judged by the extent of LTR driven CAT gene expression in the absence and presence of anti-TAR PNA. Supplementation of 100 nM of anti-TAR PNA into the culture medium further enhances the suppression of transactivation. Nonspecific scrambled PNA had no influence on Tat-TAR interaction and LTR-driven CAT gene expression in cell culture. These results suggest that PNA targeted to the TAR sequence of the viral genome may be a potential inhibitor of HIV-1 gene expression.

Antiviral Agents↗
PubMed1991

Refolded HIV-1 tat protein protects both bulge and loop nucleotides in TAR RNA from ribonucleolytic cleavage.

Substantial evidence indicates that HIV-1 trans-activation by tat protein is mediated through the TAR RNA element. This RNA forms a stem-loop structure containing a three-nucleotide bulge and a six-nucleotide loop. Previous mutagenic analysis of TAR indicates that the bulge residues and a 4 bp segment of the stem constitute, in part, the tat binding site. However, there appears to be no sequence-specific contribution of the six-base loop. We have employed a ribonuclease protection technique to explore the interaction of tat with single-stranded regions of TAR. The results indicate that tat interacts with both the bulge and loop regions of TAR. Treatment of TAR RNA with RNase A results in cleavage at U23 and U31, located in the bulge and loop regions, respectively. High concentrations (approximately 2 microM) of Escherichia coli derived tat protein, prepared by standard procedures, gave complete protection of TAR RNA from RNase A cleavage. However, under these conditions, truncated TAR derivatives in which no stem-loop structure is expected to form were also protected, indicating nonspecific binding. In order to obtain a tat preparation with enhanced specificity toward TAR RNA, methods were developed for refolding the recombinant protein. This treatment enhanced the affinity of tat for TAR by approximately 30-fold [Kd(apparent) less than 25 nM] and markedly increased its specificity for the TAR. Again, tat protected TAR RNA from RNase A cleavage at both U23 and U31. Protection was also observed with RNase T1 which cleaves TAR RNA at three G residues in the six-base loop.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1996

RNA conformation in the Tat-TAR complex determined by site-specific photo-cross-linking.

Transcriptional regulation in human immunodeficiency virus type 1 (HIV-1) requires specific interactions of Tat protein with the transactivation responsive region (TAR) RNA, a 59-base stem-loop structure located at the 5'-end of all mRNAs. We have used a site-specific cross-linking method based on 4-thiouracil (4-thioU) photochemistry to determine the conformation of TAR RNA and its interaction with Tat protein under physiological conditions. Three different TAR RNA constructs with a single 4-thioU residue at position 23, 38, or 40 were synthesized. Upon UV irradiation, 4-thioU at all three positions formed interstrand covalent cross-links in TAR RNA. Determination of cross-link sites by RNA sequencing revealed that 4-thioU at position 23 makes a direct contact with U40, while a 4-thoU at position 40 cross-links to C24 and C25, and at position 38, 4-thioU contacts G26 in TAR RNA. The addition of arginine did not alter the yield or the site of RNA-RNA cross-link. However, in the presence of Tat(38-72), UV irradiation of RNA modified with 4-thioU at position 23 or 38 resulted in RNA- protein cross-links, but no RNA-RNA cross-links were observed. 4-thioU at position 40 formed both RNA-RNA and RNA-protein cross-links in the presence of Tat(38-72). An intriguing finding of our studies was that a cross-linked TAR RNA with 4-thioU at position 40 retained specific Tat-binding activity. Our results establish four important conclusions about Tat-TAR structure. (1) U23 of free TAR RNA is in close contact with U40. (2) U40 is in close proximity to C24 and C25 both in free TAR RNA and in a complex with Tat. (3) Tat protein directly contacts U23, U38, and U40 in the major groove of TAR RNA. (4) Tat protein can recognize a TAR RNA structure containing an interrupted bulge which is formed by a covalent link between U40 and two bulge residues, C24 and C25. These structural studies provide new insights into tertiary folding of TAR RNA and its interaction with Tat protein.

Base Sequence↗
PubMed1998

A mechanism for simultaneous sensing of aspartate and maltose by the Tar chemoreceptor of Escherichia coli.

The Tar chemoreceptor of Escherichia coli exhibits partial sensory additivity. Tar can mediate simultaneous responses to two disparate ligands, aspartate and substrate-loaded maltose-binding protein (MBP). To investigate how one receptor generates concurrent signals to two stimuli, ligand-binding asymmetry was imposed on the rotationally symmetric Tar homodimer. Mutations causing specific defects in aspartate or maltose chemotaxis were introduced pairwise into plasmid-borne tar genes. The doubly mutated tar genes did not restore aspartate or maltose chemotaxis in a strain containing a chromosomal deletion of tar (delta tar). However, when Tar proteins with complementing sets of mutations were co-expressed from compatible plasmids, the resulting heterodimeric receptors enabled delta tar cells to respond to aspartate or maltose. The effect of one attractant on the response to the other depended on the relative orientations of the functional binding sites for aspartate and MBP. When the sites were in the 'same' orientation, saturating levels of one attractant strongly inhibited chemotaxis to the other. In the 'opposite' orientation, such inhibitory effects were negligible. These data demonstrate that opposing subunits of Tar can transmit signals to aspartate and maltose independently if the ligands are restricted to the 'opposite' binding orientation. When aspartate and MBP bind in the 'same' orientation, they compete for signalling through one subunit. In the wild-type Tar dimer, aspartate and MBP can bind in either the 'same' or the 'opposite' orientation, a freedom that can explain the partial additivity of the aspartate and maltose responses that is seen with tar+ cells.

ATP-Binding Cassette Transporters↗
PubMed2000

Recognition of 5'-terminal TAR structure in human immunodeficiency virus-1 mRNA by eukaryotic translation initiation factor 2.

TAR, a 59 nt 5'-terminal hairpin in human immuno-deficiency virus 1 (HIV-1) mRNA, binds viral Tat and several cellular proteins. We report that eukaryotic translation initiation factor 2 (eIF2) recognizes TAR. TAR and the AUG initiation codon domain, located well downstream from TAR, both contribute to the affinity of HIV-1 mRNA for eIF2. The affinity of TAR for eIF2 was insensitive to lower stem mutations that modify sequence and structure or to sequence changes throughout the remainder that leave the TAR secondary structure intact. Hence, eIF2 recognizes structure rather than sequence in TAR. The affinity for eIF2 was severely reduced by a 3 nt change that converts the single A bulge into a 7 nt internal loop. T1 footprinting showed that eIF2 protects nucleotides in the loop as well as in the strand opposite the A bulge. Thus, eIF2 recognizes the TAR loop and lower part of the sub-apical stem. Though not contiguous, these regions are brought into proximity in TAR by a bend in the helical structure induced by the UCU bulge; binding of eIF2 opens up the bulge context and apical stem. The ability to bind eIF2 suggests a function for TAR in HIV-1 mRNA translation. Indeed, the 3 nt change that reduces the affinity of TAR for eIF2 impairs the ability of reporter mRNA to compete in translation. Interaction of TAR with eIF2 thus allows HIV-1 mRNA to compete more effectively during protein synthesis.

Base Sequence↗
PubMed1994

Differential growth kinetics are exhibited by human immunodeficiency virus type 1 TAR mutants.

The human immunodeficiency virus type 1 (HIV-1) TAR element is critical for the activation of gene expression by the transactivator protein, Tat. Mutagenesis has demonstrated that a stable stem-loop RNA structure containing both loop and bulge structures transcribed from TAR is the major target for tat activation. Though transient assays have defined elements critical for TAR function, no studies have yet determined the role of TAR in viral replication because of the inability to generate viral stocks containing mutations in TAR. In the current study, we developed a strategy which enabled us to generate stable 293 cell lines which were capable of producing high titers of different viruses containing TAR mutations. Viruses generated from these cell lines were used to infect both T-lymphocyte cell lines and peripheral blood mononuclear cells. Viruses containing TAR mutations in either the upper stem, the bulge, or the loop exhibited dramatically decreased HIV-1 gene expression and replication in all cell lines tested. However, we were able to isolate lymphoid cell lines which stably expressed gene products from each of these TAR mutant viruses. Though the amounts of virus in these cell lines were roughly equivalent, cells containing TAR mutant viruses were extremely defective for gene expression compared with cell lines containing wild-type virus. The magnitude of this decrease in viral gene expression was much greater than previously seen in transient expression assays using HIV-1 long terminal repeat chloramphenicol acetyltransferase gene constructs. In contrast to the defects in viral growth found in T-lymphocyte cell lines, several of the viruses containing TAR mutations were much less defective for gene expression and replication in activated peripheral blood mononuclear cells. These results indicate that maintenance of the TAR element is critical for viral gene expression and replication in all cell lines tested, though the cell type which is infected is also a major determinant of the replication properties of TAR mutant viruses.

Base Sequence↗
PubMed1995

Cloning and characterization of a novel cellular protein, TDP-43, that binds to human immunodeficiency virus type 1 TAR DNA sequence motifs.

Human immunodeficiency virus type 1 (HIV-1) gene expression is modulated by both viral and cellular factors. A regulatory element in the HIV-1 long terminal repeat known as TAR, which extends from nucleotides -18 to +80, is critical for the activation of gene expression by the transactivator protein, Tat. RNA transcribed from TAR forms a stable stem-loop structure which serves as the binding site for both Tat and cellular factors. Although TAR RNA is critical for Tat activation, the role that TAR DNA plays in regulating HIV-1 gene expression is not clear. Several studies have demonstrated that TAR DNA can bind cellular proteins, such as UBP-1/LBP-1, which repress HIV-1 gene expression and other factors which are involved in the generation of short, nonprocessive transcripts. In an attempt to characterize additional cellular factors that bind to TAR DNA, a lambda gt11 expression cloning strategy involving the use of a portion of TAR DNA extending from -18 to +28 to probe a HeLa cDNA library was used. We identified a cDNA, designated TAR DNA-binding protein (TDP-43), which encodes a cellular factor of 43 kDa that binds specifically to pyrimidine-rich motifs in TAR. Antibody to TDP-43 was used in gel retardation assays to demonstrate that endogenous TDP-43, present in HeLa nuclear extract, also bound to TAR DNA. Although TDP-43 bound strongly to double-stranded TAR DNA via its ribonucleoprotein protein-binding motifs, it did not bind to TAR RNA extending from +1 to +80. To determine the function of TDP-43 in regulating HIV-1 gene expression, in vitro transcription analysis was performed. TDP-43 repressed in vitro transcription from the HIV-1 long terminal repeat in both the presence and absence of Tat, but it did not repress transcription from other promoters such as the adenovirus major late promoter. In addition, transfection of a vector which expressed TDP-43 resulted in the repression of gene expression from an HIV-1 provirus. These results indicate that TDP-43 is capable of modulating both in vitro and in vivo HIV-1 gene expression by either altering or blocking the assembly of transcription complexes that are capable of responding to Tat.

Amino Acid Sequence↗
PubMed1993

Oxygen consumption and oxyradical production from microsomal reduction of aqueous extracts of cigarette tar.

Aqueous extracts of cigarette tar (ACT) contain a quinone-hydroquinone-semiquinone system that undergoes autoxidation to produce superoxide and hydrogen peroxide. In this paper we ask whether the production of activated oxygen species from this quinone system can be enhanced via an NAD(P)H-dependent autoxidation in which electrons are donated from electron transport components of the microsomal system to electron acceptors in ACT such as quinones and/or metal chelates. Therefore, the ability of ACT to enhance the oxidation of NADPH, consumption of oxygen, and production of oxyradicals during microsomal electron transport has been investigated. Rates of NADPH oxidation and oxygen consumption are enhanced in a concentration-dependent manner by both aqueous and dimethyl sulfoxide (DMSO) extracts of tar over that observed in the presence of microsomes alone. Over the time course studied, neither NADPH oxidation nor oxygen consumption by tar extracts is observed in the absence of microsomes. Microsomal NADPH oxidation is enhanced by 1,6- and 1,3-benzo[a]pyrene quinones and by iron-EDTA; per unit weight, the enhancement by these compounds is similar to that of tar. NADPH oxidation in the presence of tar and absence of iron-EDTA is inhibited by about 15% by the addition of deferoxamine to the reaction mixture. Chrysene quinone enhances NADPH oxidation to a much greater extent than does either of the benzo[a]pyrene quinones or tar. Inhibition of tar-stimulated microsomal oxygen uptake by superoxide dismutase, stimulation of oxygen uptake by azide (an inhibitor of catalase), and the presence of spin-trappable superoxide anion radical all indicate the reduction of tar components to superoxide and hydrogen peroxide. The similar effects of tar on NADPH oxidation catalyzed either by microsomes or by purified NADPH-cytochrome P450 reductase suggest that cytochrome P450 reductase is an important locus of electron transfer from microsomes to components of cigarette tar extracts. These data suggest that the cytotoxic and mutagenic effects of smoking may be mediated by metabolic activation of quinones and, to a lesser extent, metal chelates in cigarette tar to oxyradicals.

Animals↗
PubMed2006

Comparative assessment of coal tars obtained from 10 former manufactured gas plant sites in the eastern United States.

A comparative analysis was performed on eleven coal tars obtained from former manufactured gas plant sites in the eastern United States. Bulk properties analyzed included percent ash, Karl Fisher water content, viscosity and average molecular weight. Chemical properties included monocyclic- and polycyclic-aromatic hydrocarbon (PAH) concentrations, alkylated aromatic concentrations, and concentrations of aliphatic and aromatic fractions. It was found that there was at least an order-of-magnitude variation in all properties measured between the eleven coal tars. Additionally, two coal tars obtained from the same manufactured gas plant site had very different properties, highlighting that there can be wide variations in coal tar properties from different samples obtained from the same site. Similarities were also observed between the coal tars. The relative chemical distributions were similar for all coal tars, and the coal tars predominantly consisted of PAHs, with naphthalene being the single-most prevalent compound. The C(9-22) aromatic fraction, an indicator of all PAHs up to a molecular weight of approximately 276 gmole(-1), showed a strong power-law relationship with the coal tar average molecular weight (MW (ct)). And the concentrations of individual PAHs decreased linearly as MW (ct) increased up to ca. 1000 gmole(-1), above which they remained low and variable. Implications of these properties and their variation with MW (ct) on groundwater quality are discussed. Ultimately, while these similarities do allow generalities to be made about coal tars, the wide range of coal tar bulk and chemical properties reported here highlights the complex nature of coal tars.

Coal Tar↗