Anti-HIV plant proteins catalyze topological changes of DNA into inactive forms

GAP 31, DAP 32 and DAP 30 comprise a new class of plant proteins with potent anti-HIV activity and insignificant cytotoxicity. We report here the identification and characterization of a new DNA enzyme activity in these three proteins. They irreversibly relax and decatenate supercoiled DNA, as well as catalyze double-stranded breakage to form linear DNA. The relaxed molecules are topologically inactive and no longer serve as substrates for DNA gyrase to form supercoils, phenomena similar to those of cellular topoisomerases in the presence of topoisomerase poisons. The ability of these anti-HIV agents to interrupt essential topological interconversions of DNA may provide a novel mechanism for their antiviral and antitumor actions. The presence of this new DNA topological enzyme activity in these plant proteins also suggests that their anti-HIV activity may not be merely a consequence of ribosome inactivation previously recognized.

A quantitative assay for fragmented DNA in apoptotic cells

Cleavage of cellular chromatin at internucleosomal sites is a characteristic change of DNA integrity in cells undergoing apoptosis. We have developed an assay for quantitation of internucleosomal DNA fragmentation in apoptotic cells. This technique involves purification of cellular DNA, dephosphorylation of the DNA ends, labeling of DNA with 32P at the 5'-end, gel electrophoresis through agarose, and quantitation of the radioactivity in DNA bands. This assay, which is about 1000- to 2000-fold more sensitive than visualization of DNA bands by ethidium staining, allows the detection of DNA fragments at picogram levels. A method for quantitatively determining the number of fragmented DNA strands is also described. Application of this new assay to evaluate the time course of internucleosomal DNA fragmentation was demonstrated in apoptotic cells induced by an anticancer nucleoside analogue.

The three-dimensional structure in solution (pH 5.8) of a DNA 9-mer duplex containing 1,N2-propanodeoxyguanosine opposite deoxyadenosine. Restrained molecular dynamics and NOE-based refinement calculations

The solution structure of the complementary d(C1-A2-T3-G4-X5-G6-T7-A8-C9).d(G10-T11-A12-C13-A14-C15-A 16-T17-G18) nonanucleotide duplex (designated X.A 9-mer) that contains a 1,N2-propanodeoxyguanosine exocyclic adduct, X5, opposite deoxyadenosine A14 in the center of the helix at pH 5.8 is investigated by use of restrained molecular dynamics followed by NOE-based back-calculation refinement. The molecular dynamics calculation is based on 91 interresidue and 97 intraresidue interproton distance restraints derived from two-dimensional nuclear Overhauser enhancement data on the X.A 9-mer at mixing times of 50 and 250 ms [Kouchakdjian, M., Marinelli, E., Gao, X., Johnson, F., Grollman, A., & Patel, D.J. (1989) Biochemistry 28, 5647-5657]. Separate runs start from classical A and B DNA and converge to essentially identical structures (atomic root mean square difference of 0.69 A). Both structures are B-type DNA in character and satisfy the experimental distance restraints with the rms difference of only 0.001 A between the calculated and experimental interproton distances. The dynamics behavior of the A----B DNA transition is monitored and analyzed. Our results clearly indicate that the driving force of the convergence is the experimental interproton distance restraints. The molecular dynamics structures are further refined by a back-calculation dynamics which directly minimizes the difference between the observed 2D NOE intensities and those calculated by the full relaxation matrix approach. The fit of the refined structures to the NOE intensities is measured by the NOE R value, which is analogous to the crystallographic residual index. These R values of the final structures are only 0.17. The refined structures are generally B type, and their convergency improves slightly to an atomic root mean square difference of 0.64 A, despite relatively large structural shifts (approximately 1 A) which occur during the back-calculation refinement in both cases. These results suggest that the converged refined structures represent reasonable approximations of the solution structure.

[Granule-making technology for preparing luohanguo chrysanthemum granule medicine with orthogonal design]

L9 (3(4)) orthogonal design was adopted to inspect the consumption of white sugar, water and ethanol and the duration of raw material mixing in relation to the granule-attaining rate in preparing Luohanguo-Chrysanthemum granule medicine. The result shows that with a consumption of 170 kg of white sugar, 6000 ml of water and 800 ml of ethanol and a duration of 8 minutes, the granule attaining rate reaches about 80%.

Dual mode of inhibition of purified DNA ligase I from human cells by 9-beta-D-arabinofuranosyl-2-fluoroadenine triphosphate

9-beta-D-Arabinofuranosyl-2-fluoroadenine (F-ara-A) is an analogue of adenosine and deoxyadenosine with potent anti-tumor activity. The mechanism of action for this compound has been elucidated as the inhibition of DNA and RNA synthesis, induction of DNA fragmentation, and genetic damage. This study demonstrated that DNA ligase I, an enzyme involved in DNA replication, is a target for the drug action. F-ara-adenine triphosphate (F-ara-ATP) at 80 microM inhibited the activity of DNA ligase I by more than 90%. In contrast, eight other related nucleoside analogues showed no effect on the enzyme activity at 200 microM. F-ara-ATP inhibited DNA ligation in two distinct ways. First, F-ara-ATP directly interacted with DNA ligase I and inhibited the formation of the ligase-AMP complex. This inhibition could not be reversed when free F-ara-ATP was eliminated from the treated enzyme; however, the addition of pyrophosphate, followed by gel filtration chromatography, restored enzyme activity, indicating that F-ara-ATP bound to the enzyme and altered the AMP-binding site. Secondly, the activity of DNA ligase I was inhibited when F-ara-ATP was incorporated into the 3' terminus of the DNA substrate. The dual mode of inhibition of DNA ligase I by F-ara-ATP indicates that its effect on DNA ligation may be important in the inhibition of DNA synthesis and the cytotoxicity of F-ara-A.

Selective action of 2',3'-didehydro-2',3'-dideoxythymidine triphosphate on human immunodeficiency virus reverse transcriptase and human DNA polymerases

This study used DNA primer extension and sequencing gel analyses to evaluate the molecular action of 2',3'-didehydro-2',3'-dideoxythymidine triphosphate (D4TTP), in comparison with 3'-azido-2',3'-dideoxythymidine triphosphate (AZTTP), on DNA strand elongation by human immunodeficiency virus reverse transcriptases (HIV-RT) and human DNA polymerases alpha (pol alpha) and epsilon (pol epsilon) purified from T-lymphoblastoid CEM cells. D4TTP was preferentially incorporated into the T sites of the elongating DNA strand by HIV-RT and terminated DNA synthesis at the incorporation sites. The DNA chain termination activity of D4TTP was equipotent to that of AZTTP. In contrast, D4TTP was a poor substrate for pol alpha and pol epsilon. The analogue was incorporated into DNA by the human enzymes about 10,000- to 20,000-fold less efficiently than by HIV-RT, whereas the incorporation of AZTTP by pol alpha and pol epsilon was not detectable by the DNA primer extension assay. Pol epsilon, an enzyme with 3'----5'-exonuclease activity, was unable to remove the incorporated 2',3'-didehydro-2',3'-dideoxythymidine monophosphate (D4TMP) from the 3'-end of the DNA strand, whereas 3'-azido-2',3'-dideoxythymidine monophosphate was excised from DNA by pol epsilon at about 20% of the rate for normal deoxynucleotide excision. The preferential incorporation of D4TTP by HIV-RT appears to be a molecular basis for the selective anti-HIV activity of D4T, whereas the inability of pol epsilon to remove D4TMP from DNA may be related to the cytotoxicity of this compound.

Redox-dependent changes in beta-extended chain and turn structures of cytochrome c in water solution determined by second derivative amide I infrared spectra

The redox-dependent changes in secondary structure of cytochromes c from horse, cow, and dog hearts in water at 20 degrees C have been determined by amide I infrared spectroscopy. Second derivative amide I spectra were obtained by use of a procedure that includes a convenient method for the effective subtraction of the spectrum of water vapor in the system. The band at 1657 cm-1 representing the helix structure was unaffected by a change in redox state whereas changes in bands due to turns at 1680, 1672, and 1666 cm-1, unordered structure at 1650 cm-1, and beta-structures at 1632 and 1627 cm-1 occurred. About one-fourth of the beta-extended chain spectral region and one-fifth of the beta-turn region (involving a total of approximately 9-13 residues) were sensitive to the oxidation state of heme iron. No significant changes in the secondary structure of either the reduced or oxidized protein due to changes in ionic strength were detected. The localized structural rearrangements triggered by the changes in oxidation state of heme iron are consistent with differences in the binding of heme iron to a histidine imidazole nitrogen and a methionine sulfur atom from the beta-extended chain. The demonstrated ability to obtain highly reproducible second derivative amide I infrared spectra confirms the unique utility of such spectral measurements for localization of subtle changes in secondary structure within a protein, especially for changes among the multiple turns and beta-structures.

Morphometric and stereological study of the seminal vesicle of the guinea pig

The seminal vesicle of the guinea pig has been widely used as a model for the study of hormonal action on the male accessory sex organ, but there have been few attempts to quantify their cellular and tissue components. In the present study, the seminal vesicle of the guinea pig was described in the form of a morphometric model. Tissue samples were taken from the distal, middle and proximal regions of the gland and processed for light microscopy. Using a combination of a stereological point-counting technique and direct measurement, the relative volumes of different components (lumen, epithelium, lamina propria and fibromuscular layer) were determined. The relative numbers of the secretory cells and basal cells were also estimated. Following the estimation of the average size of the seminal vesicle, the relative volume of different components and the relative number of secretory cells were transformed into absolute data on a per average seminal vesicle basis. Similarly, the average sizes of the secretory cells and nuclei were also determined. The quantitative data generated from the present study will serve as a baseline for further studies of the seminal vesicle of the guinea pig. The techniques used in the present study are easy to apply, and data generated were objective and reproducible.

[A preliminary survey on Zhuang nationality medicinal crops at traditional herbs market of Jingxi County in Guangxi Zhuang Autonomous Region]

This paper reports an investigation and study on the Zhuang nationality medicinal crops available on the traditional herbs market in Jingxi county of Guangxi Zhuang Autonomous Region. There are 380 species belonging to 129 families and 322 genus, among which notably Embelia parviflora, Malus doumeri, Panax notoginseng, Polygala fallax, etc. This study may serve as a reference for exploitation and utilization of the Zhuang nationality medicinal herbs resources.

Action of 2',2'-difluorodeoxycytidine on DNA synthesis

The action of the new deoxycytidine analogue 2',2'-difluorodeoxycytidine (dFdC) on DNA synthesis was investigated in whole cells and in vitro assay systems with purified DNA polymerases. DNA synthesis in human lymphoblastoid CEM cells was inhibited by dFdC in a concentration-dependent manner that could not be reversed by exogenous deoxynucleosides. The analogue was incorporated into cellular DNA; most of the incorporated dFdC 5'-monophosphate (dFdCMP) residues were in internucleotide linkage. In vitro DNA primer extension assays demonstrated that dFdC 5'-triphosphate (dFdCTP) competed with deoxycytidine triphosphate for incorporation into the C sites of the growing DNA strand. The ratios of the apparent Km values for the incorporation of dFdCTP and dCTP into a C site of M13mp19 DNA were 21.8 and 22.9 for DNA polymerases alpha and epsilon, respectively. The apparent Ki values of dFdCTP were 11.2 microM for DNA polymerase alpha and 14.4 microM for polymerase epsilon. After dFdCMP incorporation, the primer was extended by one deoxynucleotide before a major pause in the polymerization process was observed. This was in contrast to the action of arabinosylcytosine 5'-triphosphate, which caused both DNA polymerases alpha and epsilon to pause at the site of incorporation. The 3'----5' exonuclease activity of DNA polymerase epsilon was essentially unable to excise nucleotides from DNA containing dFdCMP at either the 3'-end or at an internal position, whereas arabinosylcytosine monophosphate was removed from the 3'-terminus at 37% the rate for deoxynucleotides. The cytotoxic activity of dFdC was strongly correlated with the amount of dFdCMP incorporated into cellular DNA. Our results demonstrate qualitative and quantitative differences in the molecular actions of dFdC and arabinosylcytosine on DNA metabolism, but are consistent with an important role for such incorporation in the toxicity of dFdC.

A new class of anti-HIV agents: GAP31, DAPs 30 and 32

Three inhibitors of human immunodeficiency virus (HIV) have been isolated and purified to homogeneity from Euphorbiaceae himalaya seeds (Gelonium multiflorum) and carnation leaves (Dianthus caryophyllus). These proteins, GAP 31 (Gelonium Anti-HIV Protein 31 kDa) and DAPs 30 and 32 (dianthus anti-HIV proteins, 30 and 32 kDa), inhibit HIV-1 infection and replication in a dose-dependent manner with little toxicity to target cells. The therapeutic indices of these compounds are in the order 10(4), suggesting that they may be clinically important agents in the treatment of AIDS. The N-terminal amino acid sequences of these proteins show little homology to those of previously described anti-HIV proteins. The structure-function features of these HIV inhibitors, based on the 40-60 amino acid residues of N-terminal sequences, are examined.

TAP 29: an anti-human immunodeficiency virus protein from Trichosanthes kirilowii that is nontoxic to intact cells

An anti-human immunodeficiency virus (anti-HIV) protein capable of inhibiting HIV-1 infection and replication has been isolated and purified to homogeneity from Trichosanthes kirilowii. This protein, TAP 29 (Trichosanthes anti-HIV protein, 29 kDa), is distinct from trichosanthin [also known as GLQ 223 (26 kDa)] in size, N-terminal amino acid sequence, and cytotoxicity. In addition to three conservative substitutions--namely, Arg-29 to Lys, Ile-37 to Val, and Pro-42 to Ser--a total difference of residues 12-16 was found. TAP 29 yielded -Lys-Lys-Lys-Val-Tyr-, whereas trichosanthin has -Ser-Ser-Tyr-Gly-Val-. Although the two proteins exhibit similar anti-HIV activity, as measured by syncytium formation, p24 expression, and HIV reverse transcriptase activity, they differ significantly in cytotoxicity, as measured by their effects on cellular DNA and protein syntheses. At the dose level of the bioassays, 0.34-340 nM, trichosanthin demonstrates a dose-dependent toxic effect on host cells. TAP 29 displays no toxic effect, even at 100 X ID50, whereas trichosanthin demonstrates 38% and 44% inhibition on cellular DNA and protein synthesis, respectively. These results indicate that the therapeutic index of TAP 29 is at least two orders of magnitude higher than that of trichosanthin. Thus TAP 29 may offer a broader safe dose range in the treatment of AIDS.

[Adult nasopharyngeal mucosa xenograft and dinitrosopiperazine carcinogenesis in nude mice]

Adult nasopharyngeal mucosa from 44 patients of chronic nasopharyngitis diagnosed by pathology were transplanted into 59 nude mice. The control group, 13 nude mice, were given no treatment. 10 16 days after transplantation, the experimental group, 46 nude mice, were subcutaneously injected dinitrosopiperazine (DNP), 15mg/kg, twice a week, for 12-30 times. In the experimental group, the xenografts in 27 nude mice were examined 18-37 weeks after transplantation, and the epithelia survived in 20 mice. The survival rate was 74.1%. The survival epithelia showed focal hyperplasia, dysplasia (7/20) and carcinomatous changes (4 carcinoma in situ and 4 early infiltrating carcinoma). The carcinoma incidence was 40%. In the control group, the xenografts in 7 nude mice were examined 8-35 weeks after transplantation, and the epithelia survived in 6 mice. The survival epithelia did not develop dysplasia or carcinomatous changes. The results suggested that DNP may induce precarcinomatous lesions and carcinomatous changes of adult nasopharyngeal epithelia in nude mice. On the basis of these results, the factors related to the carcinomatous changes of the nasopharyngeal epithelia are analyzed and discussed.

Action of 9-beta-D-arabinofuranosyl-2-fluoroadenine on RNA metabolism

The action of 9-beta-D-arabinofuranosyl-2-fluoroadenine (F-ara-A) on RNA metabolism was evaluated both in whole cells and in cell-free systems. F-ara-A was converted to its 5'-triphosphate, F-ara-ATP, in cells and then incorporated into RNA as well as DNA. F-ara-A inhibited RNA synthesis in cultured cells in a concentration-dependent manner. This inhibition was mediated mainly by F-ara-ATP. Experiments using isolated nuclei demonstrated that RNA polymerases I, II, and III accounted for 24, 73, and 3% of the total RNA synthesis activity, respectively. About 88% of the total inhibition was attributed to the suppression of RNA polymerase II activity. In cultured cells, F-ara-A was preferentially incorporated into the poly(A)+ RNA fraction. Approximately 78% of the incorporated F-ara-A monophosphate residues were located at the terminal position of the RNA chain. The incorporation of F-ara-A monophosphate into mRNA resulted in premature termination of the RNA transcript and impaired its functioning as a template for protein synthesis. The inhibitory action of F-ara-A on RNA metabolism is a unique property of this compound, differing from the action of arabinosylcytosine and arabinosyladenine.

[Anti-inflammatory, analgesic and sedative effects of Leontice kiangnanensis P.L. Chiu]

The ethanolic extract of Leontice kiangnanensis (EELK) can inhibit obviously the increased permeability of abdominal blood capillaries and the ear inflammation in mice as well as the swelling of hind paw and the proliferation of granuloma induced by cotton-pellets in rats, EELK can also raise the pain thresholds during hot-plate, formaldehyde and writhing tests in mice. Use of EELK together with pentobarbital may enhance sedative effect on mice.

Polymerase chain reaction cloning of L-type calcium channel sequences from the heart and the brain

The sequences of the highly conserved S4 regions of voltage-sensitive ion channels were used to design oligonucleotide primers for the polymerase chain reaction. Specific fragments of the cDNA encoding L-type calcium channels from the heart, brain, and skeletal muscle were amplified and cloned. The nucleotide sequences of the cardiac and brain calcium channels obtained are identical over this region, and share 78% homology with the skeletal muscle calcium channel. Comparison of the predicted amino acid sequences of our clones with those of other calcium channels reveals unexpected patterns of conservation which suggest alternative exon use.

MAP 30: a new inhibitor of HIV-1 infection and replication

A new inhibitor of human immunodeficiency virus (HIV) has been isolated and purified to homogeneity from the seeds and fruits of the Momordica charantia. This compound, MAP 30 (Momordica Anti-HIV Protein), is a basic protein of about 30 kDa. It exhibits dose-dependent inhibition of cell-free HIV-1 infection and replication as measured by: (i) quantitative focal syncytium formation on CEM-ss monolayers; (ii) viral core protein p24 expression; and (iii) viral-associated reverse transcriptase (RT) activity in HIV-1 infected H9 cells. The doses required for 50% inhibition (ID50) in these assays were 0.83, 0.22 and 0.33 nM, respectively. No cytotoxic or cytostatic effects were found under the assay conditions. These data suggest that MAP 30 may be a useful therapeutic agent in the treatment of HIV-1 infections. The sequence of the N-terminal 44 amino acids of MAP 30 has been determined.

Metabolism and action of fludarabine phosphate

Fludara I.V. (fludarabine phosphate) (9-beta-D-arabinosyl-2-fluoroadenine, F-ara-A) is an adenine nucleoside analogue resistant to adenosine deaminase that shows promising therapeutic activity in the clinical treatment of lymphocytic hematologic malignancies. F-ara-A is transported into cells, where it is converted to its 5'-triphosphate (F-ara-ATP), the principal active metabolite. Deoxycytidine kinase is the enzyme responsible for the initial step of this activation metabolism. The differential transport and phosphorylation of F-ara-A and accumulation of F-ara-ATP by normal and cancer cells may constitute the metabolic basis of its positive therapeutic index. The major action of F-ara-A is the inhibition of DNA synthesis. F-ara-ATP competes with deoxyadenosine triphosphate for incorporation into the A sites of the elongating DNA strand by DNA polymerases and terminates DNA synthesis at the incorporation sites. That action is potentiated by the decrease of cellular dATP that results from inhibition of ribonucleotide reductase by F-ara-ATP. In vitro experiments demonstrated that DNA polymerase delta is able to excise the incorporated F-ara-AMP residues from DNA with its 3' to 5' exonuclease activity. The terminal incorporation of F-ara-AMP into DNA results in deletion of genetic material. That mechanism may be responsible for the observed mutagenicity of Fludara I.V., and ultimately its cytotoxic action.

Termination of DNA synthesis by 9-beta-D-arabinofuranosyl-2-fluoroadenine. A mechanism for cytotoxicity

The action of 9-beta-D-arabinofuranosyl-2-fluoroadenine (F-ara-A) on DNA synthesis was evaluated both in whole cells and in vitro. 9-beta-D-Arabinofuranosyl-2-fluoroadenine was converted to its 5'-triphosphate 9-beta-D-arabinofuranosyl-2-fluoroadenine 5'-triphosphate (F-ara-ATP) in cells and then incorporated into DNA in a self-limiting manner. More than 94% of the analogue was incorporated into DNA at the 3' termini, indicating a chain termination action. In vitro DNA primer extension experiments further revealed that F-ara-ATP compared with dATP for incorporation into the A site of the extending DNA strand. The incorporation of F-ara-AMP into DNA resulted in termination of DNA strand elongation. Human DNA polymerase alpha incorporated more F-ara-AMP into DNA than polymerase epsilon (proliferating cell nuclear antigen-independent DNA polymerase delta) and was more sensitive to inhibition by F-ara-ATP. On the other hand, DNA polymerase epsilon was able to excise the incorporated F-ara-AMP from DNA in vitro. The incorporation of F-ara-AMP into DNA was linearly correlated both with inhibition of DNA synthesis and with loss of clonogenicity; thus it may be the mechanism of cytotoxicity.

Selective action of 3'-azido-3'-deoxythymidine 5'-triphosphate on viral reverse transcriptases and human DNA polymerases

The action of 3'-azido-3'-deoxythymidine 5'-triphosphate (N3dTTP) on DNA strand elongation catalyzed by human immunodeficiency virus type 1 reverse transcriptase was evaluated in comparison with human DNA polymerase alpha and proliferating cell nuclear antigen-independent DNA polymerase delta. Sequencing gel analysis demonstrated that the human immunodeficiency virus 1 reverse transcriptase preferentially incorporated N3dTTP into the T sites of the growing DNA strands and caused chain termination in a dose-dependent manner. This effect was observed even when the N3dTTP concentration was 0.3 microM, 100-fold less than dTTP. Studies with reverse transcriptases from avian myeloblastosis virus and Moloney murine leukemia virus showed that N3dTTP was also efficiently incorporated into DNA by these enzymes and terminated DNA strand elongation. In contrast, human DNA polymerases alpha and delta did not incorporate detectable amounts of N3dTTP into the DNA and were not inhibited by 300 microM N3dTTP. The selective incorporation of the chain-terminating nucleotide by the viral reverse transcriptases appears to be a molecular basis for the positive therapeutic index of 3'-azido-3'-deoxythymidine.