Interleukin-10 enhances tumor necrosis factor-alpha activation of HIV-1 transcription in latently infected T cells

Interleukin-10 (IL-10) is elevated in HIV-1-infected individuals and has been implicated in disease progression. We previously reported that IL-10 cooperates with tumor necrosis factor-alpha (TNF-alpha) to activate HIV-1 expression synergistically in acutely infected monocyte-derived macrophages and the chronically infected U1 promonocytic cell line. To determine whether IL-10 also cooperates with TNF-alpha to activate latent HIV-I expression in lymphocytes, we examined the effects of IL-10 on proviral expression in the chronically infected T-cell line, ACH-2. Although IL-10 inhibited HIV-1 expression acting alone, in combination with suboptimal concentrations of TNF-alpha, IL-10 increased HIV-1 steady-state mRNA expression and p24 core antigen production in ACH-2 cells. Interestingly, IL-10 concentrations that synergistically induced virus also maximally stimulated endogenous TNF-alpha expression, suggesting that cell-derived TNF-alpha may contribute to cytokine synergy. Transfection studies in ACH-2 cells indicated that IL-10 combined with TNF-alpha to activate the HIV-1 long terminal repeat (LTR). IL-10 also cooperated with TNF-alpha to activate HIV-1 LTR in 1G5 cells, a Jurkat T-cell line stably transfected with an LTR-dependent luciferase reporter gene. Pyrrolidine dithiocarbamate, a potent transcriptional inhibitor of the viral LTR, abrogated the cytokine responses in both U1 and ACH-2 cells, suggesting a common TNF-alpha-mediated transcriptional mechanism in these cell types despite their different modes of provirus latency. Taken collectively, these data suggest that IL-10 enhances suboptimal TNF-alpha activation of HIV-1 transcription in chronically infected T-cells at least in part through induction of endogenous TNF-alpha expression.

Sustained secretion of human alpha-1-antitrypsin from murine muscle transduced with adeno-associated virus vectors

Recombinant adeno-associated virus (AAV) vectors have been used to transduce murine skeletal muscle as a platform for secretion of therapeutic proteins. The utility of this approach for treating alpha-1-antitrypsin (AAT) deficiency was tested in murine myocytes in vitro and in vivo. AAV vectors expressing the human AAT gene from either the cytomegalovirus (CMV) promoter (AAV-C-AT) or the human elongation factor 1-alpha promoter (AAV-E-AT) were examined. In vitro in C2C12 murine myoblasts, the expression levels in transient transfections were similar between the two vectors. One month after transduction, however, the human elongation factor 1 promoter mediated 10-fold higher stable human AAT expression than the CMV promoter. In vivo transduction was performed by injecting doses of up to 1.4 x 10(13) particles into skeletal muscles of several mouse strains (C57BL/6, BALB/c, and SCID). In vivo, the CMV vector mediated higher levels of expression, with sustained serum levels over 800 micrograms/ml in SCID and over 400 micrograms/ml in C57BL/6 mice. These serum concentrations are 100,000-fold higher than those previously observed with AAV vectors in muscle and are at levels which would be therapeutic if achieved in humans. High level expression was delayed for several weeks but was sustained for over 15 wk. Immune responses were dependent upon the mouse strain and the vector dosage. These data suggest that recombinant AAV vector transduction of skeletal muscle could provide a means for replacing AAT or other essential serum proteins but that immune responses may be elicited under certain conditions.

Dose-dependent effects of PSC 833 on its tissue distribution and on the biliary excretion of endogenous substrates in rats

PSC 833, a nonimmunosuppressive cyclosporin, is a potent inhibitor of the efflux of antitumor drugs mediated by P-glycoprotein and thus has been introduced in clinical trials as an agent to overcome multidrug resistance. The purpose of this study was to evaluate the dose-dependent pharmacokinetics of PSC 833 and its effects on the biliary excretion of endogenous substrates in rats. The major elimination route for PSC 833 is metabolism, followed by excretion into bile. The biliary clearance of PSC 833 was reduced in a dose-dependent manner, whereas no urinary excretion of PSC 833 was detectable. The tissue/blood concentration ratios for PSC 833 in the liver, kidney, intestine, and spleen were reduced in a dose-dependent manner, suggesting the presence of a saturable uptake process and/or saturable binding in these tissues. The dose-dependent increase in the tissue/blood concentration ratio in the brain suggests the presence of efflux transporters on the blood-brain barrier. PSC 833 reduced the bile flow rate by decreasing the biliary excretion of bile acids and reduced and oxidized glutathione, in a dose-dependent manner. The mechanism for the dose-dependent disposition of PSC 833 and its effects on the biliary excretion of endogenous substrates could be related to interactions with transporters.

Apolipoprotein B signal peptide and apolipoprotein E genotypes as determinants of the hepatic secretion of VLDL apoB in obese men

We aimed to examine the effect of genetic polymorphisms of apolipoprotein B-100 (apoB) signal peptide and apolipoprotein E (apoE) on the hepatic secretion of very low density lipoprotein (VLDL) apoB in 29 men with visceral obesity. We studied apoB secretion using a primed (1 mg/kg), constant (1 mg/kg/h) intravenous infusion of [1-(13)C]leucine. The isotopic enrichment of VLDL apoB was determined using gas chromatography-mass spectrometry (GCMS). A multi-compartmental model was used to estimate the fractional turnover rate of VLDL apoB. Genotypes for the apoB signal peptide length polymorphism, 27 amino acid (SP27) and 24 amino acid (SP24), and apoE genotypes were determined using polymerase chain reaction. In subjects who were not apoE2 carriers and were homozygous for the SP27 of the apoB signal peptide, the hepatic secretion of VLDL apoB was significantly higher than in subjects who were not apoE2 carriers and were either heterozygous or homozygous for the SP24 allele (31.3 +/- 11.8 mg/kg fat-free mass/day, n = 8 vs. 16.9 +/- 12.2 mg/kg fat-free mass/day, n = 13, P = 0.01). In subjects who were not apoE4 carriers and were either heterozygous or homozygous for the apoB SP24 allele, the hepatic secretion of VLDL apoB was significantly lower than in subjects who were not apoE4 carriers and were homozygous for the SP27 allele (15.8 +/- 12.9 mg/kg fat-free mass/day, n = 13 vs. 27.4 +/- 11.5 mg/kg fat-free mass/day, n = 7, P = 0.03). The data suggest that in men with visceral obesity, the apoB signal peptide and apoE genotypes appear to be involved in the hepatic secretion of apoB.

[Study of activated protein C resistance(APC-R) and FV Leiden in healthy blood donors and patients with thrombosis]

OBJECTIVE

To study activated protein C resistance (APC-R) and FV Leiden in Chinese and their role in the pathogenesis of thrombophilia.

METHODS

APC-R was detected by activated partial thromboplastin time (APTT) in the presence and absence of APC. FV Leiden mutation was detected by PCR amplification with sequence-specific primers and restriction enzyme digestion. The subjects included 32 healthy blood donors (control), 38 patients with thrombosis in Wuhan, China, 106 patients with thrombosis in Homburg, Germany. FV Leiden mutation was screened in 12 patients in Wuhan and 106 in Homburg.

RESULTS

There was no significant difference for APC-R between healthy controls and the patients in Wuhan. No FV Leiden mutation was found in 12 patients in Wuhan. The APC-R frequency of the patients in Homburg was significantly higher than those in Wuhan (22.6% and 7.9%, respectively). Eleven patients in Hombery had FV Leiden mutation.

CONCLUSION

APC-R and FV Leiden mutation varied in different regions and races. FV Leiden may not be the main cause of thrombophilia in Chinese.

Sample purification for the analysis of caffeine in tobacco by gas chromatography-mass spectrometry

A commonly used additive to tobacco products is cocoa. A sensitive an selective method was developed to measure caffeine, a marker for cocoa, in tobacco by using gas chromatography-mass spectrometry (GC-MS). Tobacco components usually produce high background signals in GC-MS analysis. Therefore, a series of extraction steps were designed to effectively purify the tobacco extracts. The analytical recovery of caffeine was 100 when [trimethyl-13C3] caffeine was used as an isotope-dilution reference. A linear calibration curve was generated with caffeine concentration ranging from 0.01 to 20 micrograms/ml. The detection limit of caffeine was 0.02 microgram/ml in the final solution. This method was applied to several commercial tobacco products, of which the corresponding caffeine levels varied from below the detection limit to 125 micrograms/g.

Structure of holo-glyceraldehyde-3-phosphate dehydrogenase from Palinurus versicolor refined at 2 A resolution

The crystal structure of holo-glyceraldehyde-3-phosphate dehydrogenase from Palinurus versicolor, South China sea lobster, was determined and refined at 2 A resolution to an R factor of 17.1% and reasonable stereochemistry. The structure refinement has not altered the overall structure of GAPDH from this lobster species. However, some local changes in conformation and the inclusion of ordered solvent model have resulted in a substantial improvement in the accuracy of the structure. Structure analysis reveals that the two subunits including NAD+ in the asymmetric unit are remarkably similar. The thermal differences between the two subunits found in some regions of the NAD+-binding domain may originate from different crystallographic environments rather than from an inherent molecular asymmetry. In this structure, the side chain of Arg194 does not point toward the active site but forms an ion pair with Asp293 from a neighboring subunit. Structural comparisons with other GAPDH's of known structure reveal that obvious contrast exists between mesophilic and thermophilic GAPDH mainly in the catalytic domain with significant conformational differences in the S-loop, beta7-strand and loop 120-125; the P-axis interface is more conserved than the R- and Q-axis interfaces and the catalytic domain is more conserved than the NAD+-binding domain. Some possible factors affecting the thermostability of this enzyme are tentatively analyzed by comparison with the highly refined structures of thermophilic enzymes.

Structure of a basic phospholipase A2 from Agkistrodon halys Pallas at 2.13 A resolution

The basic phospholipase A2 isolated from the venom of Agkistrodon halys Pallas (Agkistrodon blomhoffii Brevicaudus) is a hemolytic toxin and one of the few PLA2's capable of hydrolyzing the phospholipids of E. coli membranes in the presence of a bactericidal/permeability-increasing protein (BPI) of neutrophils. The crystal structure has been determined and refined at 2.13 A to an R factor of 16.5% (F > 3sigma) with excellent stereochemistry. A superposition of the two molecules in the asymmetric unit gives an r. m.s. deviation of 0.326 A for all Calpha atoms. The refined structure allowed a detailed comparison with other PLA2 species of known structures. The overall architecture is similar to those of other PLA2's with a few significant differences. One of which is in the region connecting the N-terminal helix and the Ca2+-binding loop. Unexpectedly, the conformation of the peptide plane Cys29-Gly30 in the Ca2+-binding loop is very different to that of other PLA2's. The amide NH of Gly30 does not point toward the proposed site for stabilization of the tetrahedral intermediate oxyanion of the substrate analogue. The structure includes four residues which occur less frequently in other PLA2's. His1, Arg6 and Trp70 located at the interfacial recognition site may play an important role in the interaction with aggregated substrates, while Trp77 contributes to the hydrophobic interactions between the beta-wing and the main body of the molecule. This structure analysis reveals that two clusters of basic residues are located at or near the interfacial recognition site, forming an asymmetric positively charge distribution. In contrast to the acidic isoform, the present enzyme is a dimer in the crystalline state. The special phospholipid hydrolysis behaviors are discussed in the light of the structure determined.

Attenuation of age-dependent oxidative damage to DNA and protein in brainstem of Tg Cu/Zn SOD mice

Age-dependent accumulation of oxidative DNA and protein damage in brainstem and striatum was assessed in normal and transgenic (tg) mice which overexpress human Cu/Zn superoxide dismutase (h-SOD1). A marker of oxidative DNA damage, 8-hydroxy-2'-deoxyguanosine (oxo8dG), was measured at 3, 12, and 18 months of age in control and tg mice. Cu/Zn SOD, but not MnSOD, activities in brainstems and striata from tg mice were increased compared to controls at all ages. At 18 months, oxo8dG levels were increased by 58% in brainstem and by 21% in striatum of control mice. In the tg mice, brainstem and striatal oxo8dG levels were increased to a lesser extent than in the corresponding controls. Protein oxidation (carbonyl content), was increased by 59% at 18 months in control brainstem, but not in striatum, and the increase was significantly attenuated in the tg mice. In summary, oxidative damage to DNA and protein increased with age in brainstem (and to a lesser extent in striatum), and augmented Cu/Zn SOD activity modified the extent of DNA and protein damage.

[Local amyloidosis of stomach]

OBJECTIVE

To improve the diagnostic rate of local amyloidosis of stomach.

METHOD

One case of local amyloidosis of stomach was reported and the literatures were reviewed on the etiopathology, clinical features, diagnosis, treatment and prognosis.

RESULT

The patient was negative for family history and other chronic disease. Total gastrectomy was taken and was eventually found to have localized amyloidosis of stomach and regional lymph nodes. The amyloidosis was found to be of AA amyloidosis. Multiple biopsy specimens taken from esophagus, duodenum, rectum and bone marrow showed no amyloid deposition.

CONCLUSION

Amyloidosis should be considered in the differential diagnosis of gastric tumors, and also should be removed by operation if complications are to be prevented.

Priority of pentose utilization at the level of transcription: arabinose, xylose, and ribose operons

When E. coli cells were grown in minimal medium supplemented with D-ribose and D-xylose, a diauxic growth preferring D-xylose was observed. Transcription of the ribose (rbs) operon was repressed in the presence of D-xylose, phenotypically similar to catabolite repression by D-glucose, although D-ribose did not affect transcription of the xylose (xyl) operon. Complementation analysis with xylR revealed that the repression of the rbs operon by D-xylose is exerted at the transcriptional level through XylR, suggesting a novel mechanism for catabolite repression. Furthermore, it was shown that L-arabinose reduced transcriptions of both xyl and rbs operons, whereas the arabinose operon was not affected by D-xylose or D-ribose, suggesting a priority mechanism for pentose utilization.

Utilization of D-ribose through D-xylose transporter

An Escherichia coli mutant defective in high-affinity D-ribose transport is able to utilize the sugar as a sole carbon source, suggesting that other transport systems for D-ribose exist. In order to search for such transporters, transposon mutagenesis was carried out in an rbsB-negative strain containing ribokinase (rbsK) for sugar phosphorylation. Insertions showing an enhanced ribose growth were isolated and mapped in xylA and its promoter region. The mutations increased not only the ribose uptake but also the expression of xylFGH encoding an ABC (ATP-binding cassette)-type transporter for D-xylose. Secondary mutations abolishing the ribose-utilizing phenotype were obtained both in the xylFG genes coding for the xylose high-affinity transporter and in xylR that is required for the xyl gene expression. Ribose uptake was also reduced by the secondary mutations. An overexpression of xylFGH under Ptrc promoter supported enhanced growth on ribose. These results indicate that D-ribose can be transported through the XylFGH transporter.

Modulation of rat rotational behavior by direct gene transfer of constitutively active protein kinase C into nigrostriatal neurons

The modulation of motor behavior by protein kinase C (PKC) signaling pathways in nigrostriatal neurons was examined by using a genetic intervention approach. Herpes simplex virus type 1 (HSV-1) vectors that encode a catalytic domain of rat PKCbetaII (PkcDelta) were developed. PkcDelta exhibited a constitutively active protein kinase activity with a substrate specificity similar to that of rat brain PKC. As demonstrated in cultured sympathetic neurons, PkcDelta caused a long-lasting, activation-dependent increase in neurotransmitter release. In the rat brain, microinjection of HSV-1 vectors that contain the tyrosine hydroxylase promoter targeted expression to dopaminergic nigrostriatal neurons. Expression of pkcDelta in a small percentage of nigrostriatal neurons (approximately 0.1-2%) was sufficient to produce a long-term (>/=1 month) change in apomorphine-induced rotational behavior. Nigrostriatal neurons were the only catecholaminergic neurons that contained PkcDelta, and the amount of rotational behavior was correlated with the number of affected nigrostriatal neurons. The change in apomorphine-induced rotational behavior was blocked by a dopamine receptor antagonist (fluphenazine). D2-like dopamine receptor density was increased in those regions of the striatum innervated by the affected nigrostriatal neurons. Therefore, this strategy enabled the demonstration that a PKC pathway or PKC pathways in nigrostriatal neurons modulate apomorphine-induced rotational behavior, and altered dopaminergic transmission from nigrostriatal neurons appears to be the affected neuronal physiology responsible for the change in rotational behavior.

A distal regulatory region of the insulin-like growth factor binding protein-2 (IGFBP-2) gene interacts with the basic helix-loop-helix transcription factor, AP-4

Insulin-like growth factor binding protein-2 (IGFBP-2), the predominant IGFBP in the fetal circulation and an induced protein during several types of malignancies, belongs to a family of structurally related proteins that bind the mitogens, IGF-1 and IGF-2. The present study focused on functional analysis of the 5 '-flanking region (approximately 1.3 kb) of the IGFBP-2 gene to identify nuclear factors that mediate hepatic transcription of this gene. Luciferase (LUC) reporter constructs containing progressive deletions of 5'-flanking DNA and the intact promoter of the porcine IGFBP-2 gene were examined for functional activity by transient transfection of human HepG2 liver cells. LUC activity of the transfected reporter gene driven by the IGFBP-2 promoter and flanking sequences to -1397 (numbering relative to initiation codon at +1) was 22-fold higher than that of promoterless parent LUC vector. This activity was decreased by 60% with deletion of sequences to -874 bp, and dropped to basal levels with further truncation to -764 bp. The region between -874 and -765 bp (110 bp) functioned as a potent stimulator of heterologous SV40 promoter activity (110 bp/SV40-LUC construct) and was found to contain two noncontiguous basic helix-loop-helix (bHLH) transcription factor binding motifs (E-boxes [CAN NTG]: CACCTG and CAAATG). In electrophoretic mobility shift assays, nuclear proteins prepared from HepG2 cells formed two complexes (C1, C2) with double-stranded oligonucleotides containing either HLH sequence, mutations of which resulted in loss of complex formation. Southwestern blot analysis identified an HepG2 nuclear protein with molecular mass of 48 kDa, similar to that of the bHLH transcription factor AP-4, which bound the CACCTG motif. Cotransfection of HepG2 cells with the 110-bp/SV40-LUC construct and an expression vector encoding human AP-4 increased IGFBP-2 fragment-dependent SV40 promoter activity by 16-fold. This AP-4-mediated stimulation was lost following block mutation of both bHLH motifs within the IGFBP-2 110-bp fragment. Results demonstrate the functional importance of sequences upstream of the promoter in IGFBP-2 gene transcription and identify a novel mechanism by which bHLH proteins potentially may affect cell proliferation and differentiation via induction of IGFBP-2 synthesis.

[Major blood vessel excision and reconstruction in the treatment of retroperitoneal neoplasms]

OBJECTIVE

To summarize the experience in the treatment of retroperitoneal tumors involving major blood vessels.

METHODS

Twenty five cases with retroperitoneal tumors involving major blood vessels were treated by excision of the tumor and the major blood vessel involved followed by vascular reconstruction.

RESULTS

After a careful preoperative evaluation and necessary preparation, the tumor together with the involved blood vessels in all patients are successfully resected and the severed major blood vessels reconstructed. There was no operative death.

CONCLUSION

Retroperitoneal neoplasm involving major blood vessels is not a contraindication for surgical resection. The tumor and the involved vessel can be removed en bloc followed by vascular reconstruction. The risk of local tumor recurrence can thus be minimized and better survival achieved.

Serotonin receptors in the caudal brainstem are necessary and sufficient for the anorectic effect of peripherally administered mCPP

The role of caudal brainstem 5-HT receptors in mediating the anorectic effect of the direct 5-HT2C/1B agonist, mCPP [1-(3-chlorophenyl)piperazine dihydrochloride], was evaluated. We demonstrated, first, that systemic injections of mCPP yielded a dose-related suppression of intra-oral intake of 12.5% glucose in intact rats and in chronically maintained supracollicular decerebrate rats. The results of the decerebrate experiment suggest that 5-HT receptors in the caudal brainstem are sufficient for mediating the drug's intake effect. We also showed a dose-related intake suppression when mCPP was delivered to the fourth ventricle of intact rats, with potent suppression obtained at doses well below threshold for systemic administration. Whether and to what extent the 5-HT2C/2A antagonist, mesulergine reverses the intake suppression that follows systemic or 4th i.c.v. injection of mCPP was examined. Fourth i.c.v. co-administration of mesulergine (60 microg) and mCPP (40 microg) eliminated the approximately 50% intake suppression observed when mCPP was delivered alone, a result that affirms the receptor selectivity of the 4th i.c.v. agonist effect. We showed, further, that 4th i.c.v.mesulergine (60 microg) completely reversed the intake suppression produced by systemic mCPP (2 mg/kg). The latter result indicates that stimulation of 5-HT receptors in the caudal brainstem is necessary for the intake suppression produced by systemic administration of this 5-HT agonist in the intact rat.

[Reoperative treatment of recurrent retroperitoneal tumor]

OBJECTIVE

To improve the resection rate and survival rate for recurrent retroperitoneal tumor (RRT).

METHOD

We analysed 34 patients with RRT who were treated in our hospital from 1987 to 1995. One patient had benign tumor, the others malignant. Because 7 patients were operated on over one time, we performed 53 operations including complete resection in 42 patients, palliative resection 8 and biopsy 3.

RESULT

The 1-and 2-year survival rates for complete resection cases were 71.2% and 65.3%. The patients who received palliative resection and biopsy died within one year.

CONCLUSION

The diagnosis, preoperative preparation and intraoperative management of RRT are important to operative safety and survival rate. We emphasize the importance of reoperation and complete resection for RRT.

Toxicity of dieldrin for dopaminergic neurons in mesencephalic cultures

Dieldrin can be retained for decades in lipid-rich tissue and has been measured in some postmortem PD brains. Dieldrin has been reported to deplete brain monoamines in several species and has been shown to inhibit mitochondrial respiration. To further investigate the possibility that it may be involved in the pathogenesis of parkinsonism, its toxicity for dopaminergic (DA) neurons was assessed in a mesencephalic cell culture model. Primary neuronal cultures of mesencephalic neurons were prepared from fetal rats or fetal mice, grown for 1 week and incubated with Dieldrin (0.01-100 microM) for 24 or 48 h. Toxicity for DA neurons was determined by measuring density of surviving tyrosine hydroxylase immunoreactive (TH-ir) cells. Toxicity for gamma-aminobutyric acid (GABA)-ergic neurons was determined by measuring survival of glutamate decarboxylase (GAD)-ir neurons. General, nonselective cytotoxicity was determined by counting cells visualized by phase contrast microscopy or by DAPI-stained cells with fluorescence microscopy. Dieldrin exposure for 24 h resulted in a dose-dependent decrease in survival of TH-IR cells (DA neurons) with a 50% decrease (EC50) produced by 12 microM in rat mesencephalic cultures. Dieldrin also produced a dose- and time-dependent decrease in mouse DA-ergic and GABA-ergic neurons in mouse mesencephalic cultures. GABA-ergic neurons were less sensitive to the toxin compared to DA-ergic neurons. Cellular uptake of 3H-DA was also affected by lower concentrations of Dieldrin (EC50 = 7.98 microM) than uptake of 3H-GABA (EC50 = 43 microM). Thus, Dieldrin appears to be a relatively selective DA-ergic neurotoxin in mesencephalic cultures. Dieldrin, which may be ubiquitous in the environment, is proposed as an agent which can initiate and promote dopaminergic neurodegeneration in susceptible individuals.

[Study on the cellular immune function and cytokines in aplastic anemia patients]

OBJECTIVE

To evaluate the effects of cellular immune function and cytokines on the pathogenesis of aplastic anemia (AA) and its clinical significance.

METHODS

T lymphocyte subsets and HLA-DR antigen expression in the peripheral blood cells were assayed, and the levels of G-CSF, IL-6, TNF alpha, IFN alpha and IL-8 in the PBMNC culture supernatants were determined in 38 AA patients and 20 normal control with APAAP and ELISA methods.

RESULTS

CD4+ cells, CD4+/CD8+ cells and G-CSF level were lower, and CD8+ cells, HLA-DR+ cells and IL-6, TNF alpha, IFN alpha and IL-8 levels were higher in AA patients than in normal controls. The level of G-CSF was positively correlated with CD4+ cells and CD4+/CD8+ cells and negatively with IFN alpha level. IL-6 level was negatively correlated with WBC count and CD4+ cells. TNF alpha level was positively correlated with CD8+ cells and negatively with CD4+/CD8+ cells. IL-8 level was positively correlated with CD8+ cells and HLA-DR+ cells.

CONCLUSION

The cellular immune dysfunction and cytokine aberration participate in the pathogenesis of AA.

Human papillomavirus type 16 E6 and E7 oncogenes abrogate radiation-induced DNA damage responses in vivo through p53-dependent and p53-independent pathways

E6 and E7 oncoproteins from high risk human papillomaviruses (HPVs) transform cells in tissue culture and induce tumors in vivo. Both E6, which inhibits p53 functions, and E7, which inhibits pRb, can also abrogate growth arrest induced by DNA-damaging agents in cultured cells. In this study, we have used transgenic mice that express HPV-16 E6 or E7 in the epidermis to determine how these two proteins modulate DNA damage responses in vivo. Our results demonstrate that both E6 and E7 abrogate the inhibition of DNA synthesis in the epidermis after treatment with ionizing radiation. Increases in the levels of p53 and p21 proteins after irradiation were suppressed by E6 but not by E7. Through the study of p53-null mice, we found that radiation-induced growth arrest in the epidermis is mediated through both p53-dependent and p53-independent pathways. The abrogation of radiation responses in both E6 and E7 transgenic mice was more complete than was seen in the p53-null epidermis. We conclude that E6 and E7 each have the capacity to modulate p53-dependent as well as p53-independent cellular responses to radiation. Additionally, we found that the conserved region (CR) 1 and CR2 domains in E7 protein, which are involved in the inactivation of pRb function and required for E7's transforming function, were also required for E7 to modulate DNA damage responses in vivo. Thus pRb and/or pRb-like proteins likely mediate both p53-dependent and p53-independent responses to radiation.

Cloning and characterization of the promoter for the liver isoform of the rat carnitine palmitoyltransferase I (L-CPT I) gene

Carnitine palmitoyltransferase I (CPTI) catalyses the transfer of long chain fatty acids to carnitine for translocation across the mitochondrial inner membrane. The cDNAs of two isoforms of CPT I, termed the hepatic and muscle isoforms, have been cloned. Expression of the hepatic CPT I gene (L-CPT I) is subject to developmental, hormonal and tissue specific regulation. We have cloned the promoter of the L-CPTI gene from a rat genomic library. In the L-CPTI gene, there are two exons 5' to the exon containing the ATG that initiates translation. Exon 1 and the 5' end of exon 2 contain sequences that were not previously described in the rat L-CPTI cDNA. There is an alternatively spliced form of the L-CPTI mRNA in which exon 2 is skipped. The proximal promoter of the L-CPTI gene is extremely GC rich and does not contain a TATA box. There are several putative Sp1 binding sites near the transcriptional start site. A 190 base pair fragment of the promoter can efficiently drive transcription of luciferase and CAT (chloramphenicol acetyltransferase) reporter genes transiently transfected into HepG2 cells. Sequences in both the first intron and the promoter contribute to basal expression. Our results provide the foundation for further studies into the regulation of L-CPTI gene expression.

The porcine insulin-like growth factor system: at the interface of nutrition, growth and reproduction

The IGF system is implicated in the regulation of cellular response to protein- and energy-restriction. Although it is clear that the IGF and their binding proteins are profoundly influenced by dietary factors, a number of important questions remain about this relationship. In particular, although studies to date have focused on nutritional modulation of hepatic IGF gene expression, the molecular mechanisms underlying metabolic regulation of liver IGF and IGF binding protein genes remain relatively unknown. Moreover, the potential effects of altered nutrition on the expression and/or actions of IGF system components in tissues other than the liver have been examined only in cursory fashion. Many of these studies have used rats, an admittedly important model, but one which differs from the human in a potentially significant way: rats lack circulating IGF-II and IGFBP-2 during post-weaning and adult life. Here, we summarize current research on the porcine IGF system and highlight the particular usefulness this system may offer for unraveling the complex relationships of nutrition and systemic/local IGF expression and actions that are relevant to human nutritional physiology.

cDNA cloning and tissue-specific expression of the gene encoding human adenylate kinase isozyme 2

We isolated two kinds of cDNAs encoding human adenylate kinase (AK) isozyme 2 from a HeLa cell cDNA library using bovine AK2 cDNA as a probe. Nucleotide sequencing revealed that the cDNAs encoded 239- and 232-amino acid proteins with deduced molecular mass of 26.5 (AK2A) and 25.6kDa (AK2B), respectively. Northern blot analysis demonstrated that AK2 mRNA is strongly expressed in liver, heart, skeletal muscle and pancreas, and moderately in kidney, placenta and brain, and weakly in lung. However, Western blot analysis showed that AK2 protein was present in large amounts in liver, heart, kidney, and in a small amount in lung, and undetectable in brain and skeletal muscle. These results suggested the presence of the tissue-specific gene-expression including post-transcriptional regulation in expression of the AK2 gene.