Biomedical subjects

H Liu

Publications and source records attributed to H Liu.

At least 793 records · Page 44Linked to original sources

PubMed1998

[The types and distributive features of gene mutation on beta-thalassemia in three districts in northwest China].

OBJECTIVE: To sum up the results of gene analyses on beta-Thalassemia in three districts in northwest China and discuss the types and distributive features of the mutation. METHODS: Polymerase china reaction in combination with dot-blot hybridization of allele-specific oligonucleutide probes(PCR-ASO). RESULTS: In the gene analysis carried out in 85 probands with beta-Thalassemia, twelve types of gene mutation were identified from five nationalities. CD8(-AA), CDs8-9(+G), CDs27-28(+C) heterozygote and [-28(A-->uG). CD17(A-->uT)/N] double heterozygote were firstly assayed in these districts besides the common types in Chinese, of which, [-28(A-->uG). CD17(A-->uT)/N] as double gene mutation in the same chromosome is rare. CONCLUSION: There are significant differences in the distribution and nationality features of gene mutation types for beta-Thalassemia in the three districts, so the three districts as a whole is an area with special distributive features of the disease.

Adolescent↗

PubMed1998

The impacts of experimental necrotizing pancreatitis on hepatocellular ion homeostasis and energetics: an in vivo nuclear magnetic resonance study.

BACKGROUND: Liver dysfunction may be an early event or the end result of multiple organ dysfunction (MOD) in necrotizing pancreatitis. This study measured the early changes in hepatocellular ions and energetics associated with such conditions. METHODS: Twenty-five rats, prepared with a 23Na and 31P double-tuned nuclear magnetic resonance surface coil secured over the dome of the liver, were randomized into 5 groups: control, 10 and 20 minutes of total inflow ischemia, pancreatitis induced by deoxycholic acid (DCA), and sham-DCA (saline injection). Dysprosium-TTHA3- solution was used to separate the intracellular and extracellular sodium peaks. RESULTS: In rat liver, 20 minutes of total inflow occlusion caused irreversible depletion of high-energy phosphates. Changes at 2 hours after the onset of DCA-pancreatitis are compared with changes after 20 minutes of ischemia (mean +/- SEM). Although the DCA-pancreatitis animals did not become hypotensive until 1 hour after the induction of pancreatitis, the changes in hepatic intracellular ions and energetics began soon after such an insult. At 2 hours after the onset of pancreatitis, hepatocellular pHi and [NA+]i were 6.99 +/- 0.16 and 78.4 +/- mmol/L, respectively (P < .01, compared with sham animals). A similar pattern of changes in hepatic bioenergetics also occurred. After the onset of pancreatitis, the hepatic cytostolic phosphorylation potential decreased with time (y = 0.654 - 0.004t, where t is time in minutes and r2 = 0.967 and the rate of hepatic hydrolysis of adenosine triphosphate increased progressively (y = 0.702t + 91.363, where t is time in minutes and r2 = 0.969. These changes correlated well with the accumulated [Na]i. CONCLUSIONS: Unresuscitated necrotizing pancreatitis caused severe hepatocellular acidosis, profound sodium accumulation, and bioenergy depletion early in its course. These effects were as severe as those induced by total liver ischemia. Liver dysfunction may be an early, not terminal, event of MOD in necrotizing pancreatitis.

Adenosine Triphosphate↗

PubMed1997

Regulation of leukotriene A4 hydrolase activity in endothelial cells by phosphorylation.

Endothelial cells contain leukotriene (LT) A4 hydrolase (LTA-H) as detected by Northern and Western blotting, but several studies have been unable to detect the activity of this enzyme. Since LTA-H could play a key role in determining what biologically active lipids are generated by activated endothelium during the inflammatory process, we studied possible mechanisms by which this enzyme may be regulated. We find that LTA-H is phosphorylated under basal conditions in human endothelial cells and in this state does not exhibit epoxide hydrolase activity (i.e. conversion of LTA4 to LTB4). LTA-H purified from endothelial cells is efficiently dephosphorylated by incubation with protein phosphatase-1 in the presence of an LTA-H peptide substrate and not at all in the absence of substrate. Under conditions that lead to dephosphorylation, protein phosphatase-1 activates the epoxide hydrolase activity of LTA-H. Using peptide mapping and site-directed mutagenesis, we have identified serine 415 as the site of phosphorylation of LTA-H by a kinase found in endothelial cell cytosol. In parallel, we have studied a human lung carcinoma cell line that expresses active LTA-H. Although these cells have cytosolic kinases that phosphorylate recombinant LTA-H, they do not target serine 415 and thus do not inhibit LTA-H activity. We believe that LTA-H is regulated in intact cells by a kinase/phosphatase cycle and further that the kinase in endothelial cells specifically recognizes and phosphorylates a regulatory site in the LTA-H.

Amino Acid Substitution↗

PubMed1997

Single step purification of rat liver aldolase using immobilized artificial membrane chromatography.

Aldolase B is a peripheral membrane protein. Immobilized artificial membrane (IAM) surfaces were used to purify rat liver aldolase B in a single chromatographic step. Selective elution required dipalmitoylphosphatidylcholine (DPPC) to be included in the mobile phase. Selective elution of aldolase from the IAM column when DPPC (0.2 mM) was added to the mobile phase indicates that DPPC was an affinity displacing ligand for this membrane associated protein. Since tissue preparation involved only homogenization and centrifugation, the single step purification of aldolase B using IAM chromatography is a very convenient method. The IAM stationary phase (1.5 g) has a loading capacity of at least 4.39 mg total protein from rat liver homogenates and typically approximately 17.7 microg of pure aldolase in a single step from approximately 60 mg wet weight rat liver cytosol can be obtained.

Amino Acid Sequence↗

PubMed1997

MHC class I and II expression in prostate carcinoma and modulation by interferon-alpha and -gamma.

BACKGROUND: Expression of Major Histocompatibility Complex (MHC) class I and II antigens are critical for the cellular immune response. Loss of MHC expression represents one mechanism by which cancer cells escape immune recognition. PURPOSE: To define MHC class I and II expression by prostate cancer (PCa) in vivo and in vitro and the ability to modulate MHC expression in vitro with IFN-alpha and -gamma. METHODS: Frozen tissue sections of 25 benign prostatic hyperplasia (BPH) and 18 PCa specimens were studied by immunohistochemistry. PCa cell lines LNCaP, PC-3, and DU-145 were studied by FACS, ELISA, and cytospin. Class I was detected by monoclonal antibody (mAb) W6/32, and class II by mAb 13.17. The effects of IFN-alpha and -gamma were assessed by testing the three cell lines in the presence or absence of varying concentrations of the cytokine for varying incubation times. RESULTS: Class I was strongly expressed by 24/25 BPH specimens; 4/18 (22%) PCa were homogeneously class I-positive, while 5/18 (28%) were heterogeneously positive and 9/18 (50%) were class I-negative. PC-3 and DU-145 expressed normal levels of class I, while LNCaP expressed only low levels. All line except LNCaP demonstrated significant up-regulation of class I with either IFN-alpha or -gamma. Class II expression was not seen in BPH epithelium nor in 17/18 PCa. Class II could be only weakly induced in the three PCa lines. CONCLUSIONS: These findings confirm prior studies demonstrating that class I expression is commonly lost or diminished in PCa. In addition, class II up-regulation by IFN-gamma appears very limited in relation to other normal or neoplastic epithelium. IMPLICATIONS: The present findings, taken together with previous studies, are most consistent with the expression of neoantigens by PCa, which are recognized and appropriately eliminated by the cellular immune system. This selective pressure favors outgrowth of cells which down-regulate or lose class I and/or class II expression. Understanding PCa immunobiology will help in the development of effective immunotherapy for this disease.

Enzyme-Linked Immunosorbent Assay↗

PubMed1997

The complete genome sequence of the gram-positive bacterium Bacillus subtilis.

Bacillus subtilis is the best-characterized member of the Gram-positive bacteria. Its genome of 4,214,810 base pairs comprises 4,100 protein-coding genes. Of these protein-coding genes, 53% are represented once, while a quarter of the genome corresponds to several gene families that have been greatly expanded by gene duplication, the largest family containing 77 putative ATP-binding transport proteins. In addition, a large proportion of the genetic capacity is devoted to the utilization of a variety of carbon sources, including many plant-derived molecules. The identification of five signal peptidase genes, as well as several genes for components of the secretion apparatus, is important given the capacity of Bacillus strains to secrete large amounts of industrially important enzymes. Many of the genes are involved in the synthesis of secondary metabolites, including antibiotics, that are more typically associated with Streptomyces species. The genome contains at least ten prophages or remnants of prophages, indicating that bacteriophage infection has played an important evolutionary role in horizontal gene transfer, in particular in the propagation of bacterial pathogenesis.

Bacillus subtilis↗

PubMed1997

Preferential dissemination of B-cell gastric mucosa-associated lymphoid tissue (MALT) lymphoma to the splenic marginal zone.

The tendency for gastric mucosa-associated lymphoid tissue (MALT) lymphoma cells preferentially to localize around reactive B-cell follicles, both in the mucosa and regional lymph nodes, coupled with their immunophenotype, has led to the proposal that the normal cell counterpart of this lymphoma is the marginal zone B cell. In keeping with this proposition, lymphocytes expressing the lymphoma idiotype have been detected in the splenic marginal zone in a single case of gastric MALT lymphoma. To confirm that this truly represented preferential homing of MALT lymphoma to the splenic marginal zone, we have now re-examined this case, together with 17 other cases, using both immunohistochemical and molecular methods in an attempt to establish clonal identity between the gastric lymphoma and cells in the splenic marginal zone. In three cases, the spleen was characterized by marked expansion of marginal zones by cells showing the same pattern of Ig light chain restriction as the gastric lymphoma. None of the remaining 15 cases showed histologic evidence of lymphomatous infiltration. Analysis of the Ig genes by polymerase chain reaction (PCR), cloning, and sequencing confirmed clonal identity between the splenic marginal zone infiltrates and the gastric lymphoma in the histologically involved cases. Amplifiable DNA could be extracted from only 5 of the remaining 15 cases. In 3 of these cases, including the case previously studied using an anti-idiotype, involvement of the splenic marginal zone could be confirmed using microdissection and clone-specific PCR. No involvement could be detected in the remaining 2 cases. In addition, we have shown that mucosal addressin cell adhesion molecule-1 (MAdCAM-1), the primary homing receptor of gut-mucosa for lymphocytes, was strongly expressed by the sinus lining cells of the splenic marginal zone. These results provide strong evidence for preferential involvement of the marginal zone when gastric MALT lymphomas disseminate to the spleen, which is in keeping with the notion that the marginal zone B cells are the normal counterparts of MALT lymphoma cells.

Adult↗

PubMed1997

Sequence analysis of a 25-kb segment in the 17 degrees-19 degrees region of the Bacillus subtilis chromosome containing ada locus.

As a part of the Bacillus subtilis genome sequencing project, we have determined a 25-kb sequence covering the 17 degrees-19 degrees region. This region contains 26 complete open reading frames (ORFs) including the alkA and adaA/B operon, which encode genes for adaptive response to DNA alkylation. A homology search for the newly identified 21 ORFs revealed that 4 of them exhibit a significant similarity to known proteins, e.g., methicillin-resistant Staphylococcus aureus (MRSA) protein homolog, proteins involved in chloramphenicol resistance, glucosamine synthase and an ABC transporter protein. The remaining 17 ORFs did not show any significant sequence similarities to known gene products in the database.

Bacillus subtilis↗

PubMed1997

Sequence analysis of a 45-kb segment in the 19 degrees-23 degrees region of the Bacillus subtilis chromosome containing glpT and mpr loci.

The nucleotide sequence of a 45,137-bp segment covering the 19 degrees and 23 degrees region in the 360 degrees map of the Bacillus subtilis genome was determined. This region contained 45 open reading frames (ORFs) including 7 which corresponded to the products of genes with known functions that had been previously sequenced. The known genes were: glpT and glpQ for glycerol utilization pathway; purT for a part of the purine synthesis pathway; mpr for an extracellular metalloprotease; pss and psd for the parts of the phospholipid synthesis pathway; and gltP for a glutamine transporter. Deduced amino acid sequences of the 22 newly identified ORFs showed significant homologies to known gene products in the database such as a Methicillin-resistant Staphylococcus aureus (MRSA) gene which is related to drug resistance, a two-component response regulator, a series of amino acid permeases, transcriptional regulators, beta-lactamase, the phosphotransferase system (PTS) enzyme II for sugar uptake, and the eukaryotic ECA39 gene which is associated with cancer and apoptosis, etc. The remaining 16 ORFs did not show any significant sequence similarities to known gene products in the database.

Animals↗

PubMed1997

Cold ischemic injury accelerates the progression to chronic rejection in a rat cardiac allograft model.

BACKGROUND: The pathogenesis of chronic rejection likely involves an interplay between immunogenic and nonimmunogenic factors. The objective of this study was to determine the influence of cold ischemic preservation injury on the rate of progression to chronic rejection in the Lewis to F344 cardiac allograft model. METHODS: To induce an ischemic injury, donor hearts were stored for 3 hr at 4 degrees C in University of Wisconsin solution before transplantation. Allografts were excised at 1, 7, and 90 days after transplantation or at rejection. Vasculopathy was graded for degree of intimal thickening based on the involvement of vascular perimeter and luminal compromise. RESULTS: The degree of vessel injury in ischemic injured allografts at 90 days was significantly greater than in nonischemic injured allografts (2.8+/-0.4 vs. 1.6+/-0.5, P<0.05). Ischemic injury in syngeneic grafts did not induce a vasculopathy. Immunoperoxidase staining with R73 (anti-T cell) and ED1 (anti-macrophage) monoclonal antibodies revealed that, in ischemic injured allografts at 90 days after transplantation, the infiltrate was composed predominantly of T cells and macrophages. Additionally, ischemic injured allografts excised at 7 days after transplantation showed cellular infiltrates composed of R73-positive T cells and rare interleukin-2 receptor-positive cells, which was not observed in nonischemic allografts or ischemic syngeneic grafts. CONCLUSIONS: The progression to chronic vasculopathy in this model is principally an immunologic process, which is accelerated by an ischemic insult to the allograft. The vascular injury is mediated in part by T cells and macrophages.

Animals↗

PubMed1997

Inflammation increases the distribution of dorsal horn neurons that internalize the neurokinin-1 receptor in response to noxious and non-noxious stimulation.

Although the neurokinin-1 (NK-1)/substance P (SP) receptor is expressed by neurons throughout the spinal dorsal horn, noxious chemical stimulation in the normal rat only induces internalization of the receptor in cell bodies and dendrites of lamina I. Here we compared the effects of mechanical and thermal stimulation in normal rats and in rats with persistent hindpaw inflammation. Electron microscopic analysis confirmed the upregulation of receptor that occurs with inflammation and demonstrated that in the absence of superimposed stimulation, the increased receptor was, as in normal rats, concentrated on the plasma membrane. In general, noxious mechanical was more effective than noxious thermal stimulation in inducing NK-1 receptor internalization, and this was increased in the setting of inflammation. Although a 5 sec noxious mechanical stimulus only induced internalization in 22% of lamina I neurons in normal rats, after inflammation, it evoked near-maximal (98%) internalization in lamina I, produced significant changes in laminae III-VI, and expanded the rostrocaudal distribution of neurons with internalized receptor. Even non-noxious (brush) stimulation of the inflamed hindpaw induced internalization in large numbers of superficial and deep neurons. For thermal stimulation, the percentage of cells with internalized receptor increased linearly at >45 degrees C, but in normal rats, these were restricted to lamina I. After inflammation, however, the 52 degrees C stimulus also induced internalization in 25% of laminae III-IV cells. These studies provide a new perspective on the reorganization of dorsal horn circuits in the setting of persistent injury and demonstrate a critical contribution of SP.

Animals↗

PubMed1997

Diminished inflammation and nociceptive pain with preservation of neuropathic pain in mice with a targeted mutation of the type I regulatory subunit of cAMP-dependent protein kinase.

To assess the contribution of PKA to injury-induced inflammation and pain, we evaluated nociceptive responses in mice that carry a null mutation in the gene that encodes the neuronal-specific isoform of the type I regulatory subunit (RIbeta) of PKA. Acute pain indices did not differ in the RIbeta PKA mutant mice compared with wild-type controls. However, tissue injury-evoked persistent pain behavior, inflammation of the hindpaw, and ipsilateral dorsal horn Fos immunoreactivity was significantly reduced in the mutant mice, as was plasma extravasation induced by intradermal injection of capsaicin into the paw. The enhanced thermal sensitivity observed in wild-type mice after intraplantar or intrathecal (spinal) administration of prostaglandin E2 was also reduced in mutant mice. In contrast, indices of pain behavior produced by nerve injury were not altered in the mutant mice. Thus, RIbeta PKA is necessary for the full expression of tissue injury-evoked (nociceptive) pain but is not required for nerve injury-evoked (neuropathic) pain. Because the RIbeta subunit is only present in the nervous system, including small diameter trkA receptor-positive dorsal root ganglion cells, we suggest that in inflammatory conditions, RIbeta PKA is specifically required for nociceptive processing in the terminals of small-diameter primary afferent fibers.

Animals↗

PubMed1997

Solution structure of a 142-residue recombinant prion protein corresponding to the infectious fragment of the scrapie isoform.

The scrapie prion protein (PrPSc) is the major, and possibly the only, component of the infectious prion; it is generated from the cellular isoform (PrPC) by a conformational change. N-terminal truncation of PrPSc by limited proteolysis produces a protein of approximately 142 residues designated PrP 27-30, which retains infectivity. A recombinant protein (rPrP) corresponding to Syrian hamster PrP 27-30 was expressed in Escherichia coli and purified. After refolding rPrP into an alpha-helical form resembling PrPC, the structure was solved by multidimensional heteronuclear NMR, revealing many structural features of rPrP that were not found in two shorter PrP fragments studied previously. Extensive side-chain interactions for residues 113-125 characterize a hydrophobic cluster, which packs against an irregular beta-sheet, whereas residues 90-112 exhibit little defined structure. Although identifiable secondary structure is largely lacking in the N terminus of rPrP, paradoxically this N terminus increases the amount of secondary structure in the remainder of rPrP. The surface of a long helix (residues 200-227) and a structured loop (residues 165-171) form a discontinuous epitope for binding of a protein that facilitates PrPSc formation. Polymorphic residues within this epitope seem to modulate susceptibility of sheep and humans to prion disease. Conformational heterogeneity of rPrP at the N terminus may be key to the transformation of PrPC into PrPSc, whereas the discontinuous epitope near the C terminus controls this transition.

Amino Acid Sequence↗

PubMed1997

Monoclonal antibodies to the extracellular domain of prostate-specific membrane antigen also react with tumor vascular endothelium.

Prostate-specific membrane antigen (PSMA), initially defined by monoclonal antibody (mAb) 7E11, is a now well-characterized type 2 integral membrane glycoprotein expressed in a highly restricted manner by prostate epithelial cells. 7E11 has been shown to bind an intracellular epitope of PSMA that, in viable cells, is not available for binding. Herein, we report the initial characterization of the first four reported IgG mAbs that bind the external domain of PSMA. Competitive binding studies indicate these antibodies define two distinct, noncompeting epitopes on the extracellular domain of PSMA. In contrast to 7E11, these mAbs bind to viable LNCaP cells in vitro. In addition, they show strong immunohistochemical reactivity to tissue sections of prostate epithelia, including prostate cancer. These mAbs were also strongly reactive with vascular endothelium within a wide variety of carcinomas (including lung, colon, breast, and others) but not with normal vascular endothelium. These antibodies should prove useful for in vivo targeting to prostate cancer, as well as to the vascular compartment of a wide variety of carcinomas.

Animals↗

PubMed1997

Pulsed electromagnetic fields preserve proteoglycan composition of extracellular matrix in embryonic chick sternal cartilage.

The influence of pulsed electromagnetic fields (PEMF) on proteoglycan composition in cartilage extracellular matrix has been investigated. Day 16 embryonic chick sternal cartilage was explanted to culture and exposed for 3 h per day for 2 days to a repetitive single-pulse PEMF with frequency of 15 Hz and peak magnetic field of 1.25 G. PEMF treatment did not affect cell proliferation, as indicated by [3H]thymidine incorporation, but significantly stimulated the retention of glycosaminoglycans in the explants and reduced the release of glycosaminoglycans into the media. Determination of incorporation of [35S]sulfate and [3H]N-acetylglucosamine into proteoglycans in vitro and breakdown of in ovo labelled [35S]sulfated proteoglycans in vitro showed that PEMF treatment significantly suppressed the synthesis of proteoglycans and the degradation of both newly synthesized and pre-existing proteoglycans. Sepharose CL-2B chromatography demonstrated that PEMF did not affect either the size distribution of newly synthesized and pre-existing [35S]sulfated proteoglycans or their ability to aggregate with hyaluronate. Sepharose CL-6B chromatography followed by cellulose acetate electrophoresis revealed that the chain length and degree of sulfation of [35S]sulfated glycosaminoglycans were identical in control and PEMF-treated cultures. It is concluded that PEMF treatment preserved extracellular matrix integrity of cultured cartilage explants by down-regulating proteoglycan synthesis and degradation in a co-ordinated manner without affecting their gross structural nature.

Animals↗

PubMed1997

Endoplasmic reticulum chaperones GRP78 and calreticulin prevent oxidative stress, Ca2+ disturbances, and cell death in renal epithelial cells.

Activation of stress response genes can impart cellular tolerance to environmental stress. Iodoacetamide (IDAM) is an alkylating toxicant that up-regulates expression of hsp70 (Liu, H., Lightfoot, D. L., and Stevens, J. L. (1996) J. Biol. Chem. 271, 4805-4812) and grp78 in LLC-PK1 renal epithelial cells. Therefore, we used IDAM to determine the role of these genes in tolerance to toxic chemicals. Prior heat shock did not protect cells from IDAM but pretreatment with trans-4,5-dihydroxy-1,2-dithiane (DTTox), thapsigargin, or tunicamycin enhanced expression of the endoplasmic reticulum (ER) chaperones GRP78 and GRP94 and rendered cells tolerant to IDAM. Cells expressing a 524-base pair antisense grp78 fragment (pkASgrp78) had a diminished capacity to up-regulate grp78 and grp94 expression after ER stress. Protection against IDAM due to prior ER stress was also attenuated in pkASgrp78 cells suggesting that ER chaperones of the GRP family are critical for tolerance. Covalent binding of IDAM to cellular macromolecules and depletion of cellular thiols was similar in tolerant and naïve cells. However, DTTox pretreatment blocked the increases in cellular Ca2+ and lipid peroxidation observed after IDAM treatment. Overexpressing the ER Ca2+-binding protein calreticulin prevented IDAM-induced cell death, the rise in cytosolic Ca2+, and oxidative stress. Although activation of the ER stress response did not prevent toxicity due to Ca2+ influx, EGTA-AM and ruthenium red both blocked cell death suggesting that redistribution of intracellular Ca2+ to the mitochondria may be important in toxicity. The data support a model in which induction of ER stress proteins prevents disturbances of intracellular Ca2+ homeostasis, thus uncoupling toxicant exposure from oxidative stress and cell death. Multiple ER stress proteins are likely to be involved in this tolerance response.

Alkylation↗

PubMed1997

Reduction of trans-4,5-dihydroxy-1,2-dithiane by cellular oxidoreductases activates gadd153/chop and grp78 transcription and induces cellular tolerance in kidney epithelial cells.

trans-4,5-Dihydroxy-1,2-dithiane, the intramolecular disulfide form of dithiothreitol (DTTox) transcriptionally activates the stress-responsive genes gadd153(chop) and grp78. Herein, we used a renal epithelial cell line, LLC-PK1, to investigate the mechanism(s) whereby DTTox activates a molecular stress response. DTTox activated both grp78 and gadd153 transcriptionally, but gadd153 mRNA stability also increased suggesting that both transcriptional and posttranscriptional mechanisms are involved. DTTox did not activate hsp70 transcription indicating that a heat shock response was not induced. Structure-activity studies showed that DTTox analogues lacking the intramolecular disulfide were inactive. Furthermore, the ring-open intermolecular disulfide form of DTTox, 2-hydroxyethyl disulfide, was only a weak inducer of grp78 and gadd153 but was a strong inducer of hsp70 mRNA and a potent oxidant that lowered the NADPH/NADP+ ratio and depleted reduced glutathione (GSH). DTTox had little effect on the overall GSH and NADPH levels; thus cells were not undergoing oxidative stress; however, the NADPH/NADP+ ratio decreased slightly indicating that reducing equivalents were consumed. LLC-PK1 cells reduced DTTox to DTT, and the kinetics as well as the concentration dependence for reduction correlated with induction of both grp78 and gadd153 mRNA. Prior treatment with DTTox rendered cells tolerant to the potent nephrotoxicant S-(1,1,2, 2-tetrafluoroethyl)-L-cysteine. Bacitracin, an inhibitor of plasma membrane oxidoreductases, blocked DTTox reduction and gene activation as well as DTTox-induced tolerance. Thus, activation of stress genes and induction of cellular tolerance by DTTox is mediated by a novel mechanism involving cellular oxidoreductases.

Animals↗

PubMed1997

Functional RT and IN incorporated into HIV-1 particles independently of the Gag/Pol precursor protein.

The expression and incorporation of retroviral enzymes into virions in the form of Gag/Pol precursor polyproteins is believed to be important for the assembly of infectious viral particles. HIV-1 encodes a 160 kDa Gag/Pol precursor that includes Gag, protease (PR), reverse transcriptase (RT) and integrase (IN). We have developed the use of HIV accessory proteins (Vpr and Vpx) as vehicles to incorporate protein of both viral and non-viral origin into virions by expression in trans as heterologous fusion proteins (Wu et al., 1995, 1996a). To analyze the role of Gag/Pol in the formation of infectious virions, we incorporated RT and IN into HIV-1 particles in trans, as fusion partners of viral protein R (Vpr). Virions derived from an RT and IN minus proviral clone were infectious and replicated through a complete cycle of infection when RT and IN proteins were provided in trans. These results demonstrate that functional RT and IN proteins can be provided in trans, and that their expression and incorporation into virions as components of Gag/Pol are not required for the formation of infectious virions. Thus, for the first time, we have demonstrated for a human pathogenic retrovirus that processes of assembly and the function of critical viral enzymes can be unlinked. This finding will provide unique opportunities to explore retroviral RT/IN function and the role of Gag/Pol in the formation of infectious virions in the context of a replicating virus (in vivo).

Blotting, Western↗