Crystal structure of dimeric HIV-1 capsid protein

X-ray diffraction analysis of a human immunodeficiency virus (HIV-1) capsid (CA) protein shows that each monomer within the dimer consists of seven alpha-helices, five of which are arranged in a coiled coil-like structure. Sequence assignments were made for two of the helices, and tentative connectivity of the remainder of the protein was confirmed by the recent solution structure of a monomeric N-terminal fragment. The C-terminal third of the protein is mostly disordered in the crystal. The longest helices in the coiled coil-like structure are separated by a long, highly antigenic peptide that includes the binding site of an antibody fragment complexed with CA in the crystal. The site of binding of the Fab, the position of the antigenic loop and the site of cleavage between the matrix protein and CA establish the side of the dimer that would be on the exterior of the retroviral core.

Structure of the amino-terminal core domain of the HIV-1 capsid protein

The three-dimensional structure of the amino-terminal core domain (residues 1 through 151) of the human immunodeficiency virus-type 1 (HIV-1) capsid protein has been solved by multidimensional heteronuclear magnetic resonance spectroscopy. The structure is unlike those of previously characterized viral coat proteins and is composed of seven alpha helices, two beta hairpins, and an exposed partially ordered loop. The domain is shaped like an arrowhead, with the beta hairpins and loop exposed at the trailing edge and the carboxyl-terminal helix projecting from the tip. The proline residue Pro1 forms a salt bridge with a conserved, buried aspartate residue (Asp51), which suggests that the amino terminus of the protein rearranges upon proteolytic maturation. The binding site for cyclophilin A, a cellular rotamase that is packaged into the HIV-1 virion, is located on the exposed loop and encompasses the essential proline residue Pro90. In the free monomeric domain, Pro90 adopts kinetically trapped cis and trans conformations, raising the possibility that cyclophilin A catalyzes interconversion of the cis- and trans-Pro90 loop structures.

Organotropic formation and disappearance of 8-hydroxydeoxyguanosine in the kidney of Sprague-Dawley rats exposed to adriamycin and KBrO3

A form of oxidative DNA damage, 8-hydroxydeoxyguanosine (8-OHdG), was comparatively determined for 48 h in the kidney and liver isolated from Sprague-Dawley rats i.p. treated with Adriamycin; potassium bromate (KBrO3), hydroquinone and vitamin A. HPLC-ECD analysis system showed that Adriamycin and KBrO3, renal carcinogens, induced higher levels of 8-OHdG in the target organ of kidney (12-13.8 residues/10(4) dG(deoxyguanosine)) compared to those in the liver (3.4-3.8 residues/10(4) dG) and showed highly persistent levels (8 residues, 10(4) dG) in the kidney. The data suggest that the organotropic persistence of 8-OHdG may provide a useful marker for identifying target organ systems in oxidative chemical carcinogenesis and screening free radical-generating carcinogens.

Antibodies to carcinogen-DNA adducts in mice chronically exposed to polycyclic aromatic hydrocarbons

Antibodies specific for polycyclic aromatic hydrocarbon (PAH)-DNA adducts have previously been reported in human sera. In this study, we examined the association between mixed PAH exposure and PAH-DNA adduct specific antibodies in BALB/c mice. Mice were treated either by i.p. injection or by intragastric (i.g.) intubation with a mixture of seven different PAHs [benzo(a)pyrene (BP), benz(a)anthracene (BA), fluoranthene (FA), dibenz(a,h)anthracene (DBA), 3-methyl-cholanthrene (MC), chrysene (Ch), benzo(b)fluoranthene (BF)] at three doses (0, 15, 150 micrograms of each PAH) twice a week for 8 weeks. Sera were screened by direct ELISA for antibodies recognizing DNA modified by diolepoxides or epoxides of each PAH injected. In i.p. treated mice, the sera were slightly more reactive to DNAs modified with diolepoxides of BP, BA, or Ch or an epoxide of DBA than to unmodified DNA. In i.g. treated mice, the sera were more reactive to DNAs modified with diolepoxides of BA or BF than to unmodified DNA. For some PAHs, a dose-response effect was observed between sera reactivity to PAH metabolites and the dose of PAH administered. However, there was considerable variation in the immune responses among individual mice within each treatment group. When tested by competitive ELISA, none of the sera could discriminate between modified and unmodified DNA. This animal study suggests that an assessment of previous carcinogen exposure by measuring DNA adduct-specific antibodies requires further validation prior to its application to the human monitoring of carcinogen exposure.

Automated DNA sequencing and analysis of 106 kilobases from human chromosome 19q13.3

A total of 116,118 basepairs (bp) derived from three cosmids spanning the ERCC1 locus of human chromosome 19q13.3 have been sequenced with automated fluorescence-based sequencers and analysed by polymerase chain reaction amplification and computer methods. The assembled sequence forms two contigs totalling 105,831 bp, which contain a human fosB proto-oncogene, a gene encoding a protein phosphatase, two genes of unknown function and the previously-characterized ERCC1 DNA repair gene. This light band region has a high average density of 1.4 Alu repeats per kilobase. Human chromosome light bands could therefore contain up to 75,000 genes and 1.5 million Alu repeats.

Immunologic measurement of polycyclic aromatic hydrocarbon-albumin adducts in foundry workers and roofers

Roofers and iron foundry workers with high exposure to polycyclic aromatic hydrocarbons (PAH) were monitored for levels of covalent PAH serum albumin adducts, quantitated in enzymatically digested samples by a sensitive competitive enzyme-linked immunosorbent assay. Albumin adducts were higher in the foundry workers (5.22 fmol/micrograms, 0.314 mmol/mol) than in the reference group (4.07 fmol/micrograms, 0.245 mmol/mol), but only of borderline significance probably due to the small sample size. In a subset of foundry workers, a significant difference in adduct levels was observed for samples collected immediately after vacation and after six weeks of workplace exposure. The roofers also showed higher levels of adducts (5.19 fmol/micrograms, 0.312 mmol/mol) than their reference group (3.28 fmol/micrograms, 0.197 mmol/mol). These results demonstrate the feasibility of PAH protein adduct measurement as a marker of human exposure to this class of chemicals.

Bone mineral content in growing children

In order to establish the normal values of bone mineral content (BMC) (g/cm2), the BMC of 140 healthy growing children including 49 girls (aged 5 to 16 years) and 91 boys (aged 7 to 17 years) was measured using Dual Photon absorptiometry (DPA) at L2-L4 level of the spine. The BMC increased significantly with age, after stratification by age. Both male and female children aged 7 to 10 years had similar BMC, but female children had significantly higher BMC at 12 to 13 years of age. We also established regression equations. Female: BMC = 0.38 + 0.021 x age. Male: BMC = 0.45 + 0.017 x age. They may be useful in estimating BMC in unknown individuals

Quantitation of protein adducts as a marker of genotoxic exposure: immunologic detection of benzo[a]pyrene--globin adducts in mice

Immunologic methods have been developed for the determination of benzo[a]pyrene (BP)-protein adducts and validated in animals treated with [3H]BP. A previously developed antibody, 8E11, which recognizes 7 beta,8 alpha-dihydroxy-9 alpha,10 alpha-epoxy-7,8,9,10- tetrahydrobenzo[a]pyrene (BPDE-I)-modified DNA or protein as well as BPDE-I-tetraols, was used. The sensitivity of the assay was increased by enzymatic digestion of the modified protein with insoluble protease into peptides and amino acids before analysis. In a competitive enzyme-linked immunosorbent assay (ELISA) with digested BPDE-I-modified bovine serum albumin, 50% inhibition occurred at 400 fmol of adduct compared to 1450 fmol for the non-digested albumin. Analysis of globin (Gb) isolated from animals treated in vivo with 0.3-3 mg [3H]BP indicated that the ELISA could detect 90-100% of the adducts determined by radioactivity. Levels of adducts in lung and liver DNA and serum albumin were correlated with the levels of Gb adducts. Of the total radioactivity associated with hemoglobin, only less than or equal to 10% was from Gb while approximately 80% was from the heme fraction and the remainder from free BP metabolites. Significant cross-reactivity of antibody 8E11 was found with several BP-diols and phenols, suggesting that the immunoassay will not only be specific for BPDE-I adducts but will also detect adducts of other BP metabolites as well as other aromatic hydrocarbon diol epoxides. An immunoaffinity column of antibody 8E11 coupled to Sepharose 4B was used to isolate modified peptides from the digested Gb. About 65% of the applied radioactivity was retained on the column. Between 1 and 2 mg of non-modified digested Gb could be added to the sample without interfering with binding of adducts. Protein digestion and immunoaffinity chromatography should be useful for the measurement of protein adducts in biomonitoring studies.

Interlaboratory comparison of antisera and immunoassays for benzo[a]pyrene-diol-epoxide-I-modified DNA

An interlaboratory comparison of immunoassays using antisera elicited against benzo[a]pyrene-diol-epoxide-modified DNA (BPDE-I-DNA) was carried out resulting in standardization of antisera, competitors and assay conditions. The assays used included competitive enzyme-linked immunosorbent assays (ELISA) with color and fluorescence endpoint detection and an ultrasensitive enzyme radioimmunoassay (USERIA) with a radioactive endpoint. Three different antisera were compared, two of which were obtained from different rabbits immunized with the same BPDE-I-DNA and a third from an animal immunized with another BPDE-I-DNA sample. Samples of standardized BPDE-I-DNA with high (36 pmol adduct/microgram DNA; 1.2 adducts/10(2) nucleotides) and low (4.5 fmol/microgram DNA; 1.5 adducts/10(6) nucleotides) modification levels were prepared and used in each laboratory. The antisera were all elicited against DNAs modified to a high extent, and it was therefore not surprising that they detected adducts in a slightly modified DNA sample with lower efficiency than those in highly modified DNA samples. The discrepancy of antibody recognition between the highly and slightly modified samples varied between 1.4- and 11.2-fold depending on the antiserum and assay. To ascertain the quantitative capability of the immunoassays, the modification level of DNA isolated from mouse keratinocytes treated with [3H]benzo[a]pyrene was determined by radioactivity and immunoassay. These results indicated that when a biological sample is assayed against a BPDE-I-DNA standard modified in the same range as the biological samples (4.5 fmol/microgram), quantitative recovery of adducts is achieved by immunoassay. These studies resulted in the realization that interlaboratory differences in immunoassay procedure can have significant consequences for data comparison and that where possible it is preferable for laboratories to use the same antisera and modified DNA standards.

Massive edema of the ovary

Two cases of massive edema of the ovary are presented. One case included Meigs syndrome, which has not previously been associated with this disorder.