Structural basis for the inhibition of caspase-3 by XIAP

The molecular mechanism(s) that regulate apoptosis by caspase inhibition remain poorly understood. The main endogenous inhibitors are members of the IAP family and are exemplified by XIAP, which regulates the initiator caspase-9, and the executioner caspases-3 and -7. We report the crystal structure of the second BIR domain of XIAP (BIR2) in complex with caspase-3, at a resolution of 2.7 A, revealing the structural basis for inhibition. The inhibitor makes limited contacts through its BIR domain to the surface of the enzyme, and most contacts to caspase-3 originate from the N-terminal extension. This lies across the substrate binding cleft, but in reverse orientation compared to substrate binding. The mechanism of inhibition is due to a steric blockade prohibitive of substrate binding, and is distinct from the mechanism utilized by synthetic substrate analog inhibitors.

Structural basis for binding of Smac/DIABLO to the XIAP BIR3 domain

The inhibitor-of-apoptosis proteins (IAPs) regulate programmed cell death by inhibiting members of the caspase family of enzymes. Recently, a mammalian protein called Smac (also named DIABLO) was identified that binds to the IAPs and promotes caspase activation. Although undefined in the X-ray structure, the amino-terminal residues of Smac are critical for its function. To understand the structural basis for molecular recognition between Smac and the IAPs, we determined the solution structure of the BIR3 domain of X-linked IAP (XIAP) complexed with a functionally active nine-residue peptide derived from the N terminus of Smac. The peptide binds across the third beta-strand of the BIR3 domain in an extended conformation with only the first four residues contacting the protein. The complex is stabilized by four intermolecular hydrogen bonds, an electrostatic interaction involving the N terminus of the peptide, and several hydrophobic interactions. This structural information, along with the binding data from BIR3 and Smac peptide mutants reported here, should aid in the design of small molecules that may be used for the treatment of cancers that overexpress IAPs.

An azoospermic man with a de novo point mutation in the Y-chromosomal gene USP9Y

In humans, deletion of any one of three Y-chromosomal regions- AZFa, AZFb or AZFc-disrupts spermatogenesis, causing infertility in otherwise healthy men. Although candidate genes have been identified in all three regions, no case of spermatogenic failure has been traced to a point mutation in a Y-linked gene, or to a deletion of a single Y-linked gene. We sequenced the AZFa region of the Y chromosome and identified two functional genes previously described: USP9Y (also known as DFFRY) and DBY (refs 7,8). Screening of the two genes in 576 infertile and 96 fertile men revealed several sequence variants, most of which appear to be heritable and of little functional consequence. We found one de novo mutation in USP9Y: a 4-bp deletion in a splice-donor site, causing an exon to be skipped and protein truncation. This mutation was present in a man with nonobstructive azoospermia (that is, no sperm was detected in semen), but absent in his fertile brother, suggesting that the USP9Y mutation caused spermatogenic failure. We also identified a single-gene deletion associated with spermatogenic failure, again involving USP9Y, by re-analysing a published study.

The Nrf2 transcription factor contributes both to the basal expression of glutathione S-transferases in mouse liver and to their induction by the chemopreventive synthetic antioxidants, butylated hydroxyanisole and ethoxyquin

An overview is provided of the cancer chemoprevention actions of phenolic antioxidants and 6-ethoxy-1,2-dihydro-2,2,4-trimethylquinoline (ethoxyquin). These agents principally appear to exert their beneficial effects through induction of phase II drug-metabolizing enzymes such as glutathione S-transferase (GST). The requirement for oxidative metabolism of the synthetic antioxidants to carbonyl-containing compounds, including quinones, in order that they can induce gene expression is discussed. Previous work has shown that the basic leucine zipper transcription factor Nrf2 is involved in induction of GST by the phenolic antioxidant butylated hydroxyanisole (BHA). Evidence is provided from a mouse possessing a targeted disruption of the Nrf2 gene that, in murine liver, the transcription factor regulates basal expression of several class Alpha and class Mu GST subunits, but not class Pi GST. In the Nrf2 knock-out mouse, hepatic induction of class Alpha and class Mu GST by BHA and the synthetic antioxidant ethoxyquin is similarly impaired, suggesting that these agents affect gene activation by a related mechanism. Significantly, residual induction of GST by antioxidants is apparent in the Nrf2 mutant mouse, indicating the existence of an alternative mechanism of gene activation.

NMR structure and mutagenesis of the inhibitor-of-apoptosis protein XIAP

The inhibitor-of-apoptosis (IAP) family of proteins, originally identified in baculoviruses, regulate programmed cell death in a variety of organisms. IAPs inhibit specific enzymes (caspases) in the death cascade and contain one to three modules of a common 70-amino-acid motif called the BIR domain. Here we describe the nuclear magnetic resonance structure of a region encompassing the second BIR domain (BIR2) of a human IAP family member, XIAP (also called hILP or MIHA). The structure of the BIR domain consists of a three-stranded antiparallel beta-sheet and four alpha-helices and resembles a classical zinc finger. Unexpectedly, conserved amino acids within the linker region between the BIR1 and BIR2 domains were found to be critical for inhibiting caspase-3. The absence or presence of these residues may explain the differences in caspase inhibition observed for different truncated and full-length IAPs. Our data further indicate that these residues may bind to the active site and that the BIR domain may interact with an adjacent site on the enzyme.

NMR structure and mutagenesis of the third Bir domain of the inhibitor of apoptosis protein XIAP

The inhibitor of apoptosis proteins (IAPs) regulate the caspase family of cysteine proteases, which play an important role in the execution of programmed cell death. Human X-linked inhibitor of apoptosis protein (XIAP) is a potent inhibitor of caspases-3, -7, and -9. Here we show that the Bir3 domain is the minimal region of XIAP that is needed for potent caspase-9 inhibition. The three-dimensional structure of the Bir3 domain of XIAP, determined by NMR spectroscopy, resembles a classical zinc finger and consists of five alpha-helices, a three-stranded beta-sheet, and a zinc atom chelated to three cysteines and one histidine. The structure of the Bir3 domain is similar to that of the Bir2 domain of XIAP but differs from the previously determined structure of the Bir3 domain of MIHB. Based on site-directed mutagenesis, we have identified the regions of the Bir3 domain of XIAP that are important for inhibiting caspase-9. Despite the structural similarities of the Bir2 and Bir3 domain of XIAP, a different set of residues were found to be critical for inhibiting the individual caspases. These results suggest that XIAP inhibits caspase-3 and caspase-9 in a different manner.

ERG oncoprotein expression in prostate cancer: clonal progression of ERG-positive tumor cells and potential for ERG-based stratification

Gene fusions prevalent in prostate cancer (CaP) lead to the elevated expression of the ERG proto-oncogene. ERG activation present in 50–70% of prostate tumors underscores one of the most common oncogenic alterations in CaP. Despite numerous reports of gene fusions and mRNA expression, ERG oncoprotein status in CaP still remains to be defined. Furthermore, development of ERG protein-based assays may provide a new dimension to evaluation of gene fusions involving diverse androgen-regulated promoters and the ERG protein-coding sequence. Through exhaustive evaluations of 132 whole-mount prostates (261 tumor foci and over 200 000 benign glands) for the ERG oncoprotein nuclear expression, we demonstrated 99.9% specificity for detecting prostate tumor cells using a highly specific anti-ERG monoclonal antibody. The ERG oncoprotein expression correlated well with fusion transcript or gene fusion in randomly selected specimens. Strong concordance of ERG-positive foci of prostatic intraepithelial neoplasia (PIN) with ERG-positive carcinoma (82 out of 85 sections with PIN, 96.5%) affirms the biological role of ERG in clonal selection of prostate tumors in 65% (86 out of 132) of patients. Conversely, ERG negative PINs were associated with ERG-negative carcinoma. Taken together, the homogeneous and strong ERG expression detected in individual tumors establishes the potential for ERG oncoprotein-based stratification of CaP.

Influence of crystal structure on the tableting properties of sulfamerazine polymorphs

PURPOSE

To understand the influence of polymorphic structure on the tableting properties of sulfamerazine.

METHODS

Bulk powders of sulfamerazine polymorph I and of two batches. II(A) and II(B) of different particle size, of polymorph II were crystallized. The powders were compressed to form tablets whose porosity and tensile strength were measured. The relationships between tensile strength, porosity and compaction pressure were analyzed by the method developed by Joiris. E., et al. Pharm. Res. 15:1122-1130 (1998).

RESULTS

The sensitivity of tensile strength to compaction pressure, known as the tabletability, follows the order. I >> II(A) > II(B) and the porosity at the same compaction pressure, which measures the compressibility, follows the order, I << II(A) < II(B). Therefore. the superior tabletability of I over II(A) or II(B) is attributed to its greater compressibility. Molecular simulation reveals slip planes in crystals of I but not in II. Slip planes provide I crystals greater plasticity and therefore greater compressibility and tabletability. Larger crystal size of II(B) than of II(A) leads to fewer contact points between crystals in the tablets and results in a slightly lower tabletability.

CONCLUSIONS

Slip planes confer greater plasticity to crystals of I than II and therefore greater tabletability.

Deletion of azoospermia factor a (AZFa) region of human Y chromosome caused by recombination between HERV15 proviruses

Deletion of any of three regions of the human Y chromosome results in spermatogenic failure and infertility. We previously sequenced one of these regions, azoospermia factor a (AZFa) and found that it spanned approximately 800 kb. By sequence-tagged site (STS) content mapping, we roughly defined deletion breakpoints in two unrelated, azoospermic men with AZFa deletions. The positions of proximal and distal breakpoints were similar in the two men. Hypothesizing that the deletions might have been generated by homologous recombination, we searched electronically for DNA sequence similarities between the proximal and distal breakpoint regions. These comparisons revealed the most striking sequence similarities anywhere along or near the AZFa region. In the proximal breakpoint region, we identified a 10 kb provirus of the recently defined HERV15 class of endogenous retroviruses. In the distal breakpoint region, we found a second HERV15 provirus, 94% identical in DNA sequence to the first and in the same orientation. (A partial LINE insertion in this distal provirus proved to be the basis of the previously described DYS11/p12f polymorphism.) The AZFa deletions in the two men differed slightly, but all breakpoints fell within the HERV15 proviruses. Indeed, sequencing of deletion junctions from the two men revealed that homologous recombination had occurred within large domains of absolute sequence identity between the proximal and distal proviruses. When combined with published STS mapping data for other AZFa-deleted men, our findings suggest that recombination between these two HERV15 proviruses could account for most AZFa deletions.

Estrogen enhances the functions of CD4(+)CD25(+)Foxp3(+) regulatory T cells that suppress osteoclast differentiation and bone resorption in vitro

Cross-talk has been shown to occur between the immune system and bone metabolism pathways. In the present study, we investigated the impact of CD4(+)CD25(+)Foxp3(+) regulatory T (Treg) cells on osteoclastogenesis and bone resorption. Treg cells that were isolated and purified from peripheral blood mononuclear cells (PBMCs) of healthy adults inhibited both the differentiation of osteoclasts (OCs) from human embryo bone marrow cells (BMCs) and the pit formation in a dose-dependent manner. In cell cocultures, the production levels of both interleukin-10 (IL-10) and transforming growth factor-beta 1 (TGF-β1) were proportionally upregulated as the ratio of Treg cells to BMCs was increased, and the inhibition of OC differentiation and bone resorption by Treg cells was completely reversed by anti-IL-10 and anti-TGF-β1 antibodies. Treatment of BMC and Treg cell cocultures with 17β-estradiol (E2) at concentrations between 10⁻⁷ and 10⁻⁹ mol/l suppressed OC differentiation and bone resorption more efficiently than it did in cultures of BMCs alone; this enhanced suppression occurred via the stimulation of Treg cell IL-10 and TGF-β1 expression. These data suggest that Treg cells suppress OC differentiation and bone resorption by secreting IL-10 and TGF-β1. E2 enhances the suppressive effects of Treg cells on OC differentiation and bone resorption by stimulating IL-10 and TGF-β1 secretion from these cells. Therefore, Treg cell-derived IL-10 and TGF-β1 are likely involved in the regulation of E2 on bone metabolism and represent potential therapeutic targets for the treatment of postmenopausal osteoporosis (PMO).

A comparison of C/B ratios from studies using receiver operating characteristic curve analysis

In receiver operating characteristic (ROC) curve analysis, the optimal cutoff value for a diagnostic test can be found on the ROC curve where the slope of the curve is equal to (C/B) x (1-p[D])/p[D], where p[D] is the disease prevalence and C/B is the ratio of net costs of treating nondiseased individuals to net benefits of treating diseased individuals. We conducted a structured review of the medical literature to examine C/B ratios found in ROC curve analysis. Only two studies were found in which a C/B ratio was explicitly calculated; in another 11 studies, a C/B ratio was based on a so-called holistic estimate, an all-encompassing educated estimate of the relative costs and benefits relevant to the clinical situation. The C/B ratios ranged from 0.0025 (tuberculosis screening) to 2.7 (teeth restoration for carious lesions). Clinical scenarios that are directly life threatening but curable had C/B ratios of less than 0.05. This analysis led us to construct a table of ordered C/B ratios that may be used by investigators to approximate C/B ratios for other clinical situations in order to establish cutpoints for new diagnostic tests.

Evaluation of 14- and 11-gauge directional, vacuum-assisted biopsy probes and 14-gauge biopsy guns in a breast parenchymal model

PURPOSE

To compare commercially available 14-guage core biopsy guns and 11- and 14-gauge, directional, vaccum-assisted biopsy probes for tissue yield and fragmentation.

MATERIALS AND METHODS

One hundred passes were made through fresh turkey breasts by using each of 11 14-gauge, automated biopsy gun-needle combinations and a directional, stereotactic, vacuum-assisted biopsy system equipped with 11- or 14-gauge probes. Specimens were measured for total weight, individual length, diameter, and number of fragments.

RESULTS

Among the handheld devices, the Pro-Mag 2.2 gun (Manan Medical Products, Northbrook, Ill) and 14-gauge Biopsy-Cut needle (Bard, Covington, Ga) had the greatest yield (17.7 mg per core specimen); this combination also produced the greatest percentage of nonfragmented cores (83%). Directional, vacuum-assisted biopsy specimens were significantly larger (P < .001): 36.8 mg per core specimen for the 14-gauge probe and 94.4 mg per core specimen for the 11-gauge probe. Specimens obtained with directional, vacuum-assisted biopsy were more fragmented than those obtained with spring-actuated, two-stage, long-throw, automated biopsy systems.

CONCLUSION

Statistically significant differences with various biopsy devices are seen in the breast tissue yield and in fragmentation.

On the size of the DNA in the mammalian chromosome. Structural subunits

Alkaline degradation of mammalian DNA indicates that the molecule exists in the chromosome as an array of structural subunits. The size of the subunit of single-stranded DNA is circa 5 x 10(8) daltons, and it is of sufficient length to contain a number of synthetic units, replicons. The upper size limit of the multicomponent structure is in excess of 10(10) daltons. Mammalian cells of three different origins have been shown to contain the same basic structural DNA components and these components exist throughout the cell cycle. The nature of the links between the subunits is not known.

Validation of germination rate and root elongation as indicator to assess phytotoxicity with Cucumis sativus

Germination rate and root elongation, as a rapid phytotoxicity test method, possess several advantages, such as sensitivity, simplicity, low cost and suitability for unstable chemicals or samples. These advantages made them suitable for developing a large-scale phytotoxicity database and especially applicable for developing quantitative structure-activity relationship (QSAR) to study mechanisms of phytotoxicity. In this paper, the comparative inhibition of germination rate and root elongation of Cucumis sativus by selected halogen-substituted phenols and anilines were determined. The suitability of germination rate and root elongation as phytotoxicity endpoints was evaluated. Excellent reproducibility and stability of germination rate and root elongation in the control test, relatively greater sensitivity and similar dose-response relations for all tested compounds were observed. These results together with those of a 2-day test were used to demonstrate the suitability of this phytotoxicity test method. A QSAR was developed for the phytotoxicity mode of action of the tested compounds to C sativus seeds. Models that combined the logarithm of 1-octanol/water partition coefficient (log Kow) and the energy of the lowest unoccupied molecular orbital (Elumo) were developed for both germination rate inhibition and root elongation inhibition. The results of these studies indicate that phytotoxicity of substituted phenols and anilines to C. sativus seeds could be explained by a polar narcosis mechanism. This paper will promote the application of germination rate and root elongation method and the development of large-scale phytotoxicity database, which will provide the fundamental data for QSAR and ecological risk assessment of organic pollutants.

Dbp3p, a putative RNA helicase in Saccharomyces cerevisiae, is required for efficient pre-rRNA processing predominantly at site A3

In Saccharomyces cerevisiae, ribosomal biogenesis takes place primarily in the nucleolus, in which a single 35S precursor rRNA (pre-rRNA) is first transcribed and sequentially processed into 25S, 5.8S, and 18S mature rRNAs, leading to the formation of the 40S and 60S ribosomal subunits. Although many components involved in this process have been identified, our understanding of this important cellular process remains limited. Here we report that one of the evolutionarily conserved DEAD-box protein genes in yeast, DBP3, is required for optimal ribosomal biogenesis. DBP3 encodes a putative RNA helicase, Dbp3p, of 523 amino acids in length, which bears a highly charged amino terminus consisting of 10 tandem lysine-lysine-X repeats ([KKX] repeats). Disruption of DBP3 is not lethal but yields a slow-growth phenotype. This genetic depletion of Dbp3p results in a deficiency of 60S ribosomal subunits and a delayed synthesis of the mature 25S rRNA, which is caused by a prominent kinetic delay in pre-rRNA processing at site A3 and to a lesser extent at sites A2 and A0. These data suggest that Dbp3p may directly or indirectly facilitate RNase MRP cleavage at site A3. The direct involvement of Dbp3p in ribosomal biogenesis is supported by the finding that Dbp3p is localized predominantly in the nucleolus. In addition, we show that the [KKX] repeats are dispensable for Dbp3p's function in ribosomal biogenesis but are required for its proper localization. The [KKX] repeats thus represent a novel signaling motif for nuclear localization and/or retention.

Selective FLT3 inhibition of FLT3-ITD+ acute myeloid leukaemia resulting in secondary D835Y mutation: a model for emerging clinical resistance patterns

Acquired resistance to selective FLT3 inhibitors, is an emerging clinical problem in the treatment of FLT3-ITD⁺ acute myeloid leukaemia (AML). The paucity of valid pre-clinical models has limited investigations to determine the mechanism of acquired therapeutic resistance, thereby limiting the development of effective treatments. We generated selective FLT3 inhibitor-resistant cells by treating the FLT3-ITD⁺ human AML cell line MOLM-13 in vitro with the FLT3-selective inhibitor MLN518, and validated the resistant phenotype in vivo and in vitro. The resistant cells, MOLM-13-RES, harboured a new D835Y tyrosine kinase domain (TKD) mutation on the FLT3-ITD⁺ allele. Acquired TKD mutations, including D835Y, have recently been identified in FLT3-ITD⁺ patients relapsing after treatment with the novel FLT3 inhibitor, AC220. Consistent with this clinical pattern of resistance, MOLM-13- RES cells displayed high relative resistance to AC220 and Sorafenib. Furthermore, treatment of MOLM-13-RES cells with AC220 lead to loss of the FLT3 wild type allele and duplication of the FLT3-ITD-D835Y allele. Our FLT3-Aurora kinase inhibitor, CCT137690, successfully inhibited growth of FLT3-ITD-D835Y cells in vitro and in vivo, suggesting that dual FLT3-Aurora inhibition may overcome selective FLT3 inhibitor resistance, in part due to inhibition of Aurora kinase, and may benefit patients with FLT3-mutated AML.

Intraabdominal desmoplastic small-cell tumors with divergent differentiation. Observations on three cases of childhood

We studied three intraabdominal tumors that manifested in childhood and were attached to peritoneum, and in which the histologic pattern suggested metastatic tumor of epithelial nature but gave no evidence of a primary neoplasm in the major abdominal organs. Follow-up observation lasted from 1 to 6 years but never disclosed a primary site. Histologic, immunohistochemical, and electronmicroscopic observations indicated a primitive malignant neoplasm of uncertain histogenesis capable of simultaneously expressing epithelial, mesenchymal, and, less consistently, neural phenotypes. In childhood, the possibility of embryonic neoplasm, such as nephroblastoma occurring in atypical sites, is difficult to exclude. Despite the prevailing uncertainty about histogenesis, combined therapy achieved an apparent cure in one of our cases.

Effects of initial particle size on the tableting properties of L-lysine monohydrochloride dihydrate powder

L-lysine monohydrochloride (LMH) dihydrate was crystallized and the resulting powder was sieved to obtain various size fractions. The influence of other factors, such as crystallinity and crystal shape, was minimized by using the same batch of crystals. Compression of smaller particles at low compaction pressures resulted in tablets of greater porosity. The differences in porosity decreased with increasing compaction pressure. At the same compaction pressure, smaller particles formed tablets of greater tensile strength. However, fragmentation of the larger particles tended to equalize the particle size and reduce its influence. The differences were reduced for particles larger than 710 microm. For crystals of all size fractions, tensile strength increased with increasing compaction pressure. The tensile strength increased more rapidly for smaller crystals. Tensile strength decreased exponentially with increasing porosity for all fractions. The dependence of tensile strength on porosity is explained in term of tablet structure. Yield strength, calculated from 'out-of-die' Heckel analysis, increased with increasing particle size.

Another discontinuous epitope on glycoprotein gp120 that is important in human immunodeficiency virus type 1 neutralization is identified by a monoclonal antibody

To define the domains in the envelope glycoprotein important for antibody neutralization of the human immunodeficiency virus type 1 (HIV-1), monoclonal antibodies (mAbs) were generated by immunizing mice with purified glycoprotein gp120 of the IIIB isolate. One mAb, G3-4, reacted with the gp120 of homologous (IIIB) and heterologous (RF) isolates. In addition, mAb G3-4 efficiently neutralized both IIIB and RF viruses in vitro, as well as four of nine primary HIV-1 isolates. In competition immunoassays, mAb G3-4 and soluble CD4 were found to inhibit one another in binding to gp120. However, no competition was seen between mAb G3-4 and mAbs directed to the third variable region or the fourth conserved region of gp120. In particular, mAb G3-4 did not compete with our human mAb 15e, which identifies a discontinuous epitope on gp120 involved in group-specific neutralization of HIV-1 and in gp120-CD4 binding. Epitope-mapping studies on mAb G3-4 with synthetic or unglycosylated recombinant peptides were negative, suggesting that its epitope may be discontinuous. Indeed, this hypothesis was confirmed by showing the loss of mAb G3-4 serologic reactivity when gp120 was first denatured. We conclude that the site recognized by mAb G3-4 represents another discontinuous epitope on gp120 important for neutralization of HIV-1.

Hybrid x-ray/optical luminescence imaging: characterization of experimental conditions

PURPOSE

The feasibility of x-ray luminescence imaging is investigated using a dual-modality imaging system that merges x-ray and optical imaging. This modality utilizes x-ray activated nanophosphors that luminesce when excited by ionizing photons. By doping phosphors with lanthanides, which emit light in the visible and near infrared range, the luminescence is suitable for biological applications. This study examines practical aspects of this new modality including phosphor concentration, light emission linearity, detector damage, and spectral emission characteristics. Finally, the contrast produced by these phosphors is compared to that of x-ray fluoroscopy.

METHODS

Gadolinium and lanthanum oxysulfide phosphors doped with terbium (green emission) or europium (red emission) were studied. The light emission was imaged in a clinical x-ray scanner with a cooled CCD camera and a spectrophotometer; dose measurements were determined with a calibrated dosimeter. Using these properties, in addition to luminescence efficiency values found in the literature for a similar phosphor, minimum concentration calculations are performed. Finally, a 2.5 cm agar phantom with a 1 cm diameter cylindrical phosphor-filled inclusion (diluted at 10 mg/ml) is imaged to compare x-ray luminescence contrast with x-ray fluoroscopic contrast at a superficial location.

RESULTS

Dose to the CCD camera in the chosen imaging geometry was measured at less than 0.02 cGy/s. Emitted light was found to be linear with dose (R(2)= 1) and concentration (R(2)= 1). Emission peaks for clinical x-ray energies are less than 3 nm full width at half maximum, as expected from lanthanide dopants. The minimum practical concentration necessary to detect luminescent phosphors is dependent on dose; it is estimated that subpicomolar concentrations are detectable at the surface of the tissue with typical mammographic doses, with the minimum detectable concentration increasing with depth and decreasing with dose. In a reflection geometry, x-ray luminescence had nearly a 430-fold greater contrast to background than x-ray fluoroscopy.

CONCLUSIONS

X-ray luminescence has the potential to be a promising new modality for enabling molecular imaging within x-ray scanners. Although much work needs to be done to ensure biocompatibility of x-ray exciting phosphors, the benefits of this modality, highlighted in this work, encourage further study.

454 EST analysis detects genes putatively involved in ginsenoside biosynthesis in Panax ginseng

Panax ginseng C.A. Meyer is one of the most highly valued medicinal plants in the world. To analyze the transcriptome of P. ginseng and discover the genes involved in ginsenoside biosynthesis, cDNAs derived from the total RNA of 11-year-old, wood-grown P. ginseng roots were analyzed by 454 sequencing. A total of 217,529 high quality reads (expressed sequence tags, ESTs), with an average length of 409 bases, were generated from a one-quarter run to yield 31,741 unique sequences. The majority (20,198; 63.6%) of the unique sequences were annotated using BLAST similarity searches. A total of 16,810 and 16,577 unique sequences were assigned to functional classifications and biochemical pathways based on Gene Ontology analysis and the Kyoto Encyclopedia of Genes and Genomes assignment, respectively. Nine genes involved in the biosynthesis of ginsenoside skeletons and many candidate genes putatively responsible for modification of the skeletons, including 133 cytochrome P450s and 235 glycosyltransferases, were identified. From these candidates, six transcripts encoding UDP-glycosyltransferases that were most likely to be involved in ginsenoside biosynthesis were selected. These results open a new avenue by which to explore and exploit biosynthetic and biochemical properties that may lead to drug improvement. These 454 ESTs will provide the foundation for further functional genomic research into the traditional herb P. ginseng or its closely related species.

Gliotoxin is a dual inhibitor of farnesyltransferase and geranylgeranyltransferase I with antitumor activity against breast cancer in vivo

Gliotoxin is a natural mycotoxin with immunosuppressive and antimicrobial activity. Inhibition of farnesyltransferase (IC50 80 microM) and geranylgeranyltransferase I (IC50 17 microM) stimulated interest in the potential antitumor activity of this epidithiodioxopiperazine. Gliotoxin inhibited proliferation of six breast cancer cell lines in culture with mean +/- SD IC50 289 +/- 328 microM (range 38-985 microM); intracellular farnesylation of Lamin B and geranylgeranylation of Rap1A were inhibited in a dose-dependent manner. In randomized controlled studies using the N-methyl-N-nitrosourea rat mammary carcinoma model, gliotoxin had pronounced antitumor activity in vitro and little systemic toxicity when administered to 10 animals at 10 mg/kg by subcutaneous injection weekly for 4 wk compared with 10 controls. Single doses up to 25 mg/kg were well tolerated. The present studies confirm that gliotoxin is a dual inhibitor of farnesyltransferase and geranylgeranyltransferase I with pronounced antitumor activity and favorable toxicity profile against breast cancer in vitro and in vivo.