AMP deaminase inhibitors. 5. Design, synthesis, and SAR of a highly potent inhibitor series

A highly potent AMP deaminase (AMPDA) inhibitor series was discovered by replacing the N3 substitutents of the two lead AMPDA inhibitor series with a conformationally restricted group. The most potent compound, 3-[2-(3-carboxy-4-bromo-5,6,7,8-tetrahydronaphthyl)ethyl]-3,6,7,8-tetrahydroimidazo[4,5-d][1,3]diazepin-8-ol (24b), represents a 10- to 250-fold enhancement in AMPDA inhibitory potency without loss in the enzyme specificity. The potency of the inhibitor 24b (AMPDA K(i) = 0.002 microM) is 10(5)-fold lower than the Km for the substrate AMP. It represents the most potent nonnucleotide AMPDA inhibitor known.

Molecular systematics of Xenocyprinae (teleostei: cyprinidae): taxonomy, biogeography, and coevolution of a special group restricted in East Asia

We surveyed mitochondrial DNA (mtDNA) sequence variation in the subfamily Xenocyprinae from China and used these data to estimate intraspecific, interspecific, and intergeneric phylogeny and assess biogeographic scenarios underlying the geographic structure of lineages. We sequenced 1140 bp of cytochrome b from 30 individuals of Xenocyprinae and one putative outgroup (Myxocypris asiaticus) and also sequenced 297 bp of ND4L, 1380 bp of ND4, 68 bp of tRNA(His), and 69 bp of tRNA(Ser) from 17 individuals of Xenocyprinae and the outgroup (M. asiaticus). We detected high levels of nucleotide variation among populations, species, and genera. The phylogenetic analysis suggested that Distoechodon hupeinensis might be transferred to the genus Xenocypris, the taxonomic status of the genus Plagiognathops might be preserved, and species of Xenocypris and Plagiognathops form a monophyletic group that is sister to the genus Distoechodon and Pseudobrama. The introgressive hybridization might occur among the populations of X. argentea and X. davidi, causing the two species to not be separated by mtDNA patterns according to their species identification, and the process and direction of hybridization are discussed. The spatial distributions of mtDNA lineages among populations of Xenocypris were compatible with the major geographic region, which indicated that the relationship between Hubei + Hunan and Fujian is closer than that between Hubei + Hunan and Sichuan. From a perspective of parasite investigation, our data suggested that the fauna of Hexamita in Xenocyprinae could be used to infer the phylogeny of their hosts.

Mutation detection by capillary denaturing high-performance liquid chromatography using monolithic columns

The high resolving power of the chromatographic separation of single- and double-stranded nucleic acids in 200 microm i.d. monolithic poly(styrene-divinylbenzene) capillary columns was utilized for mutation screening in polymerase chain reaction amplified polymorphic loci. Recognition of mutations is based on the separation of homo- and heteroduplex species by ion-pair reversed-phase high-performance liquid chromatography (IP-RP-HPLC) under partially denaturing conditions, resulting in characteristic peak patterns both for homozygous and heterozygous samples. Six different single nucleotide substitutions and combinations thereof were confidently identified in 413 bp amplicons from six heterozygous individuals each of which yielded a different unique chromatographic profile. Alternatively, mutations were identified in short, 62 bp PCR products upon their complete on-line denaturation at 75 degrees C taking advantage of the ability of IP-RP-HPLC to resolve single-stranded nucleic acids of identical length that differ in a single nucleotide. Separations in monolithic capillary columns can be readily hyphenated to electrospray ionization mass spectrometry and promise increased sample throughput by operating in arrays similar to those already used in capillary electrophoresis.

The minimum alveolar concentration of enflurane for laryngeal mask airway extubation in deeply anesthetized children

The end-tidal anesthetic gas concentration required to prevent the anesthetized patient from coughing or moving during or immediately after the laryngeal mask airway (LMA) extubation is not known. We sought to determine the minimum alveolar concentration of enflurane required for the removal of the LMA in children. We studied 21 nonpremedicated children between 4 and 11 yr of age, ASA physical status I, undergoing procedures below the umbilicus. General anesthesia was induced with a mask by using sevoflurane, nitrous oxide, and oxygen, and the LMA was inserted. Anesthesia was maintained with enflurane, nitrous oxide, and oxygen. At the end of surgery, a predetermined end-tidal enflurane concentration was achieved, and the LMA was removed. Each concentration at which the LMA extubation was attempted was predetermined by the up-and-down method (with 0.1% as a step size). When LMA removal was accomplished without coughing, clenching teeth, or gross purposeful muscular movements during or within 1 min after removal, it was considered a successful LMA removal. Removal was considered to be unsuccessful in patients who developed breath holding or laryngospasm during or immediately after LMA removal. The minimum alveolar concentration of enflurane at which 50% of children had a successful LMA removal was found to be 1.02% (95% CL, 0.95%-1.11%), and the 95% effective dose for successful extubation was 1.14% (95% CL, 1.07%-1.66%). In conclusion, the LMA removal may be accomplished without coughing or moving at 1.02% end-tidal enflurane concentration in 50% of anesthetized children aged 4-11 yr.

IMPLICATIONS

There may be fewer problems associated with the laryngeal mask airway extubation when patients are deeply anesthetized. The purpose of this study was to determine the minimum concentration of enflurane for successful removal of the laryngeal mask in children.

Light-induced rotation of a transmembrane alpha-helix in bacteriorhodopsin

Spin labeling EPR spectroscopy has been used to characterize light-induced conformational changes of bacteriorhodopsin (bR). Pairs of nitroxide spin labels were attached to engineered cysteine residues at strategic positions near the cytoplasmic ends of transmembrane alpha-helices B, F, and G in order to monitor distance changes upon light activation. The EPR analysis of six doubly labeled bR mutants indicates that the cytoplasmic end of helix F not only tilts outwards, but also rotates counter-clockwise during the photocycle. The direction of the rotation of helix F is the opposite of the clockwise rotation previously reported for bovine rhodopsin. The opposite chirality of the F helix rotation in the two systems is perhaps related to the differences in the cis-trans photoisomerization of the retinal in the two proteins. Using time-resolved EPR, we monitored the rotation of helix F also in real time, and found that the signal from the rotation arises concurrently with the reprotonation of the retinal Schiff base.

High-titer, wild-type free recombinant adeno-associated virus vector production using intron-containing helper plasmids

Recombinant adeno-associated virus (rAAV) is capable of directing long-term, high-level transgene expression without destructive cell-mediated immune responses. However, traditional packaging methods for rAAV vectors are generally inefficient and contaminated with replication-competent AAV (rcAAV) particles. Although wild-type AAV is not associated with any known human diseases, contaminating rcAAV particles may affect rAAV gene expression and are an uncontrolled variable in many AAV gene transfer studies. In the current study, a novel strategy was designed to both optimize AAV rep gene expression and increase vector yield, as well as simultaneously to diminish the potential of generating rcAAV particles from the helper plasmid. The strategy is based on the insertion of an additional intron in the AAV genome. In the AAV infectious clone, the intron insertion had no effects on the properties of Rep proteins expressed. Normal levels of both Rep and Cap proteins were expressed, and the replication of the AAV genome was not impaired. However, the generation of infectious rcAAV particles using intronized AAV helper was greatly diminished, which was due to the oversized AAV genome caused by the insertion of the artificial introns. Moreover, the rAAV packaging was significantly improved with the appropriate choice of intron and insertion position. The intron is another element that can regulate the rep and cap gene expression from the helper plasmid. This study provides for a novel AAV packaging system which is highly versatile and efficient. It can not only be combined with other AAV packaging systems, including rep-containing cell lines and herpes simplex virus hybrid packaging methods, but also be used in other vector systems as well.

The role of hexokinase in plant sugar signal transduction and growth and development

Previous studies have revealed a central role of Arabidopsis thaliana hexokinases (AtHXK1 and AtHXK2) in the glucose repression of photosynthetic genes and early seedling development. However, it remains unclear whether HXK can modulate the expression of diverse sugar-regulated genes. On the basis of the results of analyses of gene expression in HXK transgenic plants, we suggest that three distinct glucose signal transduction pathways exist in plants. The first is an AtHXK1-dependent pathway in which gene expression is correlated with the AtHXK1-mediated signaling function. The second is a glycolysis-dependent pathway that is influenced by the catalytic activity of both AtHXK1 and the heterologous yeast Hxk2. The last is an AtHXK1-independent pathway in which gene expression is independent of AtHXK1. Further investigation of HXK transgenic Arabidopsis discloses a role of HXK in glucose-dependent growth and senescence. In the absence of exogenous glucose, plant growth is limited to the seedling stage with restricted true leaf development even after a 3-week culture on MS medium. In the presence of glucose, however, over-expressing Arabidopsis or yeast HXK in plants results in the repression of growth and true leaf development, and early senescence, while under-expressing AtHXK1 delays the senescence process. These studies reveal multiple glucose signal transduction pathways that control diverse genes and processes that are intimately linked to developmental stages and environmental conditions.

Improving synthetic lethal screens by regulating the yeast centromere sequence

The synthetic lethal screen is a useful method in identifying novel genes functioning in an alternative pathway to the gene of interest. The current synthetic lethal screen protocol in yeast is based on a colony-sectoring assay that allows direct visualization of mutant colonies among a large population by their inability to afford plasmid loss. This method demands an appropriate level of stability of the plasmid carrying the gene of interest. YRp-based plasmids are extremely unstable and complete plasmid loss occurs within a few generations. Consequently, YCp plasmids are the vector of choice for synthetic lethal screens. However, we found that the high-level stability of YCp plasmids resulted in a large number of false positives that must be further characterized. In this study, we attempt to improve the existing synthetic lethal screen protocol by regulating the plasmid stability and copy number. It was found that by placing a yeast centromere sequence under the control of either inducible or constitutive promoters, plasmid stability can be significantly decreased. Hence, altering the conditions under which yeast cells carrying the plasmid PGAL1-CEN4 were cultivated allowed us to develop a method that eliminated virtually 100% of false positives and drastically reduced the time required to carry out a synthetic lethal screen.

A region in domain II of the urokinase receptor required for urokinase binding

The urokinase receptor is composed of three homologous domains based on disulfide spacing. The contribution of each domain to the binding and activation of single chain urokinase (scuPA) remains poorly understood. In the present paper we examined the role of domain II (DII) in these processes. Repositioning DII to the amino or carboxyl terminus of the molecule abolished binding of scuPA as did deleting the domain entirely. By using alanine-scanning mutagenesis, we identified a 9-amino acid continuous sequence in DII (Arg(137)-Arg(145)) required for both activities. Competition-inhibition and surface plasmon resonance studies demonstrated that mutation of Lys(139) and His(143) to alanine in soluble receptor (suPAR) reduced the affinity for scuPA approximately 5-fold due to an increase in the "off rate." Mutation of Arg(137), Arg(142), and Arg(145), each to alanine, leads to an approximately 100-fold decrease in affinity attributable to a 10-fold decrease in the apparent "on rate" and a 6-fold increase in off rate. These differences were confirmed on cells expressing variant urokinase receptor. suPAR-K139A/H143A displayed a 50% reduction in scuPA-mediated plasminogen activation activity, whereas the 3-arginine variant was unable to stimulate scuPA activity at all. Mutation of the three arginines did not affect binding of a decamer peptide antagonist of scuPA known to interact with DI and DIII. However, this mutation abolished both the binding of soluble DI to DII-III in the presence of scuPA and the synergistic activation of scuPA mediated by DI and wild type DII-DIII. These data show that DII is required for high affinity binding of scuPA and its activation. DII does not serve merely as a spacer function but appears to be required for interdomain cooperativity.

Mutational analysis of the adeno-associated virus type 2 (AAV2) capsid gene and construction of AAV2 vectors with altered tropism

Adeno-associated virus type 2 (AAV2) has proven to be a valuable vector for gene therapy. Characterization of the functional domains of the AAV capsid proteins can facilitate our understanding of viral tissue tropism, immunoreactivity, viral entry, and DNA packaging, all of which are important issues for generating improved vectors. To obtain a comprehensive genetic map of the AAV capsid gene, we have constructed 93 mutants at 59 different positions in the AAV capsid gene by site-directed mutagenesis. Several types of mutants were studied, including epitope tag or ligand insertion mutants, alanine scanning mutants, and epitope substitution mutants. Analysis of these mutants revealed eight separate phenotypes. Infectious titers of the mutants revealed four classes. Class 1 mutants were viable, class 2 mutants were partially defective, class 3 mutants were temperature sensitive, and class 4 mutants were noninfectious. Further analysis revealed some of the defects in the class 2, 3, and 4 mutants. Among the class 4 mutants, a subset completely abolished capsid formation. These mutants were located predominantly, but not exclusively, in what are likely to be beta-barrel structures in the capsid protein VP3. Two of these mutants were insertions at the N and C termini of VP3, suggesting that both ends of VP3 play a role that is important for capsid assembly or stability. Several class 2 and 3 mutants produced capsids that were unstable during purification of viral particles. One mutant, R432A, made only empty capsids, presumably due to a defect in packaging viral DNA. Additionally, five mutants were defective in heparan binding, a step that is believed to be essential for viral entry. These were distributed into two amino acid clusters in what is likely to be a cell surface loop in the capsid protein VP3. The first cluster spanned amino acids 509 to 522; the second was between amino acids 561 and 591. In addition to the heparan binding clusters, hemagglutinin epitope tag insertions identified several other regions that were on the surface of the capsid. These included insertions at amino acids 1, 34, 138, 266, 447, 591, and 664. Positions 1 and 138 were the N termini of VP1 and VP2, respectively; position 34 was exclusively in VP1; the remaining surface positions were located in putative loop regions of VP3. The remaining mutants, most of them partially defective, were presumably defective in steps of viral entry that were not tested in the preliminary screening, including intracellular trafficking, viral uncoating, or coreceptor binding. Finally, in vitro experiments showed that insertion of the serpin receptor ligand in the N-terminal regions of VP1 or VP2 can change the tropism of AAV. Our results provide information on AAV capsid functional domains and are useful for future design of AAV vectors for targeting of specific tissues.

Granulocyte-macrophage colony-stimulating factor priming plus papillomavirus E6 DNA vaccination: effects on papilloma formation and regression in the cottontail rabbit papillomavirus--rabbit model

A cottontail rabbit papillomavirus (CRPV) E6 DNA vaccine that induces significant protection against CRPV challenge was used in a superior vaccination regimen in which the cutaneous sites of vaccination were primed with an expression vector encoding granulocyte-macrophage colony-stimulating factor (GM-CSF), a cytokine that induces differentiation and local recruitment of professional antigen-presenting cells. This treatment induced a massive influx of major histocompatibility complex class II-positive cells. In a vaccination-challenge experiment, rabbit groups were treated by E6 DNA vaccination, GM-CSF DNA inoculation, or a combination of both treatments. After two immunizations, rabbits were challenged with CRPV at low, moderate, and high stringencies and monitored for papilloma formation. As expected, all clinical outcomes were monotonically related to the stringency of the viral challenge. The results demonstrate that GM-CSF priming greatly augmented the effects of CRPV E6 vaccination. First, challenge sites in control rabbits (at the moderate challenge stringency) had a 0% probability of remaining disease free, versus a 50% probability in E6-vaccinated rabbits, and whereas GM-CSF alone had no effect, the interaction between GM-CSF priming and E6 vaccination increased disease-free survival to 67%. Second, the incubation period before papilloma onset was lengthened by E6 DNA vaccination alone or to some extent by GM-CSF DNA inoculation alone, and the combination of treatments induced additive effects. Third, the rate of papilloma growth was reduced by E6 vaccination and, to a lesser extent, by GM-CSF treatment. In addition, the interaction between the E6 and GM-CSF treatments was synergistic and yielded more than a 99% reduction in papilloma volume. Finally, regression occurred among the papillomas that formed in rabbits treated with the E6 vaccine and/or with GM-CSF, with the highest regression frequency occurring in rabbits that received the combination treatment.

The Saccharomyces cerevisiae RAD6 group is composed of an error-prone and two error-free postreplication repair pathways

The RAD6 postreplication repair and mutagenesis pathway is the only major radiation repair pathway yet to be extensively characterized. It has been previously speculated that the RAD6 pathway consists of two parallel subpathways, one error free and another error prone (mutagenic). Here we show that the RAD6 group genes can be exclusively divided into three rather than two independent subpathways represented by the RAD5, POL30, and REV3 genes; the REV3 pathway is largely mutagenic, whereas the RAD5 and the POL30 pathways are deemed error free. Mutants carrying characteristic mutations in each of the three subpathways are phenotypically indistinguishable from a single mutant such as rad18, which is defective in the entire RAD6 postreplication repair/tolerance pathway. Furthermore, the rad18 mutation is epistatic to all single or combined mutations in any of the above three subpathways. Our data also suggest that MMS2 and UBC13 play a key role in coordinating the response of the error-free subpathways; Mms2 and Ubc13 form a complex required for a novel polyubiquitin chain assembly, which probably serves as a signal transducer to promote both RAD5 and POL30 error-free postreplication repair pathways. The model established by this study will facilitate further research into the molecular mechanisms of postreplication repair and translesion DNA synthesis. In view of the high degree of sequence conservation of the RAD6 pathway genes among all eukaryotes, the model presented in this study may also apply to mammalian cells and predicts links to human diseases.

4,5-Diazafluoren-9-one benzoylhydrazone monohydrate

The title compound, C(18)H(12)N(4)O.H(2)O, adopts the keto tautomeric form and the azomethine C=N double bond is in the E configuration. The dihedral angle between the planes of the diazafluorene moiety and the phenyl ring is 11.3 (1) degrees. In the solid state, the molecules form infinite chain-like structures via O-H.N hydrogen bonds involving the water molecules and diazafluorene moieties.

[Otogenic hypertrophic cranial pachymeningitis associated with edema of the temporal lobe and organic mental disorder-case report]

OBJECTIVE

Hypertrophic cranial pachymeningitis(HCP) is a rare disease which might be misdiagnosed. One typical case of otogenic hypertrophic cranial pachymeningitis (HCP) associated with edema of the temporal lobe and organic mental disorder was reported. Literatures associated with HCP were reviewed for reference.

METHODS

In July, 1997, a 26-year-old man was admitted for right-sided severe headache, dizziness, nausea, vomiting, facial and abducens nerve palsy. MRI and CT revealed inflammation in the temporal bone and locally thickened dura mater with obvious enhancement as a band in the petrous apex and nearby tentorium cerebellum. The patient then underwent operation including decompression of the facial nerve, labyrinthectomy, and eradication of the inflammatory cells in the mastoid and petrous portion. Postoperatively, the clinical signs disappeared except hearing loss. Seven months later, the patient suffered from mental disorder with interrupted excitement to hit and abuse the family members. He was then treated in a psychosis hospital but no improvement could be seen. On May 13, 1998, MRI and the enhanced MRI demonstrated diffuse thickened tentorium cerebellum and dura mater in the middle cranial fossa. The inferior portion of the temporal lobe was obvious edema. The internal carotid artery was partially occluded due to the thickened wall of cavernous sinus.

RESULTS

Hence, the diagnosis of HCP associated with edema of temporal lobe and organic mental disorder was established. The patient was cured by high dosage of penicillin.

CONCLUSION

MRI is an essential method for diagnosis of HCP. Antibiotic was an effective treatment.

[The imbalance of Th1/Th2 cytokine expression in peripheral blood mononuclear cell from asthmatic patients and the effect of erythromycin on these cytokines]

OBJECTIVE

To observe the state of Th1/Th2 cytokine expression in peripheral blood mononuclear cells (PBMCs) from asthmatic patients and the effect of erythromycin (Ery) on it.

METHODS

23 asthmatic patients and 10 healthy volunteers were included. The mRNA expression for Th1/Th2 cytokines in PBMC before and after the culture with Ery were detected by RT-PCR, considering IL-2 and IFN-gamma as Th1 cytokines, and IL-4, IL-6, IL-10 as Th2 ones.

RESULTS

The positive rate of mRNA expression for Th2-derived IL-4, IL-6, IL-10 in the study group were 18/23, 19/23 and 10/23 respectively, and those for IFN-gamma and IL-2 produced by Th1 cells were 1/23 and 13/23, respectively. In the control group, the positive rate for IL-4, IL-6, IL-10 were 0/10, 2/10 and 1/10, respectively, and those for IL-2 and IFN-gamma were both 1/10. Comparing with the control group, the positive rate of mRNA expression for IL-4 and IL-6 in PBMC from asthmatic patients were significantly higher (P = 0.00003, 0.001 respectively). After the culture with Ery for 48 h, the positive rate for IL-4 expression in the study group decreased from 18/23 to 5/23 (P = 0.0006), and IL-6 from 19/23 to 9/23 (P = 0.006). The positive rate for IFN-gamma expression was elevated while IL-2 decreased(But both had no statistical significance). There was no difference observed before and after the culture with Ery in the control group.

CONCLUSIONS

There is a predominant expression of Th2-type cytokines in PBMC from asthmatic patients. Ery can down-regulate the mRNA expression for IL-4 and IL-6 in asthmatic patients, and might convert the imbalance of Th1/Th2 cytokine expression in asthmatic patients.

The Saccharomyces cerevisiae mre11(ts) allele confers a separation of DNA repair and telomere maintenance functions

The yeast Mre11 protein participates in important cellular functions such as DNA repair and telomere maintenance. Analysis of structure-function relationships of Mre11 has led to identification of several separation-of-function mutations as well as N- and C-terminal domains essential for Mre11 meiotic and mitotic activities. Previous studies have established that there is a strong correlation between Mre11 DNA repair and telomere maintenance functions and that Mre11-Rad50-Xrs2 complex formation appears to be essential for both of these activities. Here we report that the mre11(ts) allele, previously shown to cause temperature-dependent defects in DNA repair and meiosis, confers a temperature-independent telomere shortening, indicating that mre11(ts) is a separation-of-function mutation with respect to DNA repair and telomere maintenance. In a yeast two-hybrid system, Mre11(ts) fails to form a homodimer or interact with Rad50 and Xrs2 irrespective of experimental temperatures. These observations collectively suggest that the Pro(162)Ser substitution in Mre11(ts) confers a novel separation of Mre11 mitotic functions. Moreover, we observed that while overexpression of the 5'-3' exonuclease gene EXO1 partially complements the MMS sensitivity of mre11, rad50, and xrs2 null mutants, it has no effect on telomere shortening in these strains. This result provides additional evidence on possible involvement of distinctive mechanisms in DNA repair and telomere maintenance by the Mre11-Rad50-Xrs2 complex.

[Evaluation of polymerase chain reaction for detection of chlamydia trachomatis in eye swabs]

OBJECTIVE

To investigate the clinical value of Polymerase Chain Reaction (PCR) in the diagnosis of trachoma.

METHODS

Direct amplication of 16S rRNA gene which is chlamydia-specific by PCR was used to detect chlamydia trachomatis (CT).

RESULTS

Of 93 subjects who conformed to the diagnosis criteria of trachoma, 69 (74.2%) was PCR-Positive; Of 178 subjects who did not comform to the criteia, 6(3.4%) was PCR-positive. PCR had a sensitivity of 74.2% and a speciticity of 96.7% for the clinical diagnosis of trachoma. The difference between trachoma group and nontrachoma group is significant(P < 0.001).

CONCLUSION

The PCR may be a good method in the diagnosis of ocular chlamydia trachomatis infection because of its excellent sensitivity and specificity.

[Rapid detection of alpha-thalassemia of Southeast Asian deletion by polymerase chain reaction and its application to prenatal diagnosis]

OBJECTIVE

To establish a rapid and simple polymerase chain reaction (PCR) method for detecting alpha-thalassemia of Southeast Asia deletion, and apply it to the prenatal diagnosis for high risk fetuses.

METHODS

Two pairs of primers were designed: one pair bridging the breakpoints to identify the specific deletion, the other located in the common deletion region of --(SEA), -alpha(3.7) and -alpha(4.2) gene to detect the normal chromosomes. In this system, the two amplifications ran in the same PCR tube under identical condition.

RESULTS

A 740 bp fragment was amplified in chromosomes with --(SEA) determinant and a 1,052 bp fragment in normal chromosomes. For prenatal diagnosis, 3 of 8 at-risk cases were diagnosed as normal, 3 as heterozygotes, and 2 as homozygotes of --(SEA) deletion.

CONCLUSION

This detection method is rapid and accurate and can be used as a routine method for carrier detection and prenatal diagnosis.

Route of administration determines induction of T-cell-independent humoral responses to adeno-associated virus vectors

Vectors based on adeno-associated viruses (AAV) type 2 show promise for treating chronic diseases because transgene expression appears to be stable. This study evaluated the impact of humoral immunity to the capsid proteins on vector uptake by hepatocytes following an intravascular approach. Route of vector administration in mice had a qualitative effect on antivector B cell responses. Administration of vector into the tail vein resulted in T-cell-dependent (TD) B cell responses that were completely inhibited with depleting CD4 antibody. Delivery of vector into the portal circulation via the spleen yielded B cell response that were partially T cell independent (TI) rendering strategies based on T cell inhibition ineffective in allowing vector readministration. The TI B cell response was short lived in comparison to the TD response. Rhesus monkeys produced a B cell memory response to intraportal vector which appeared to be T cell dependent based on Ig isotypes. Gene therapy strategies that require AAV vector readministration should consider vector biodistribution and its impact on B cell activation.

RNase-L-dependent destabilization of interferon-induced mRNAs. A role for the 2-5A system in attenuation of the interferon response

The 2-5A system is an interferon-regulated RNA degradation pathway with antiviral, growth-inhibitory, and pro-apoptotic activities. RNase-L mediates the antiviral activity through the degradation of viral RNAs, and the anticellular effects of the 2-5A system are thought to be similarly mediated through the degradation of cellular transcripts. However, specific RNase-L-regulated cellular RNAs have not been identified. To isolate candidate RNase-L substrates, differential display was used to identify mRNAs that exhibited increased expression in RNase-L-deficient N1E-115 cells as compared with RNase-L-transfected cells. A novel interferon-stimulated gene encoding a 43-kDa ubiquitin-specific protease, designated ISG43, was identified in this screen. ISG43 expression is induced by interferon and negatively regulated by RNase-L. ISG43 induction is a primary response to interferon treatment and requires a functional JAK/STAT signaling pathway. The kinetics of ISG43 induction were identical in wild type and RNase-L knock-out fibroblasts; however, the decline in ISG43 mRNA following interferon treatment was markedly attenuated in RNase-L knock-out fibroblasts. The delayed shut-off kinetics of ISG43 mRNA corresponded to an increase in its half-life in RNase-L-deficient cells. ISG15 mRNA also displayed RNase-L-dependent regulation. These findings identify a novel role for the 2-5A system in the attenuation of the interferon response.

UBC13, a DNA-damage-inducible gene, is a member of the error-free postreplication repair pathway in Saccharomyces cerevisiae

The Ubc13 protein was recently identified for its unique role in ubiquitin (Ub) chain assembly at the Ub Lys-63 residue instead of the conventional Lys-48 residue. This activity requires Ubc13 to form a complex with Mms2 and indeed ubc13 and mms2 mutations have been shown elsewhere to be epistatic with respect to UV sensitivity. The MMS2 gene is known to be a member of the error-free DNA postreplication repair (PRR) pathway. By contrast, the Ub Lys-63 residue has been previously implicated in the error-prone PRR pathway, since yeast cells carrying the ubiK63R mutation are defective in UV-induced mutagenesis. In the present study, we attempted to define the role of UBC13 within the PRR pathway. We found that the ubc13 mutation is epistatic to mms2 and rad6, confirming that UBC13 belongs to the PRR-pathway. We also found that ubc13 is synergistic to the error-prone PRR pathway mutation rev3, indicating that UBC13 is in a pathway alternative to REV3 mutagenesis. The ubc13 mutant displays up to a 30-fold increase in the spontaneous mutation rate, and this increase is largely REV3 dependent. In addition, UV-induced mutagenesis is fully functional in the ubc13 mutant. These results together demonstrate that UBC13 is a member of the error-free PRR pathway. The involvement of UBC13 in cellular tolerance to DNA-damage is further implicated by our finding that the UBC13 transcript level is increased up to 6-fold in response to DNA-damage.

Humoral immunity to adeno-associated virus type 2 vectors following administration to murine and nonhuman primate muscle

Adeno-associated virus (AAV) is being developed as a vector capable of conferring long-term gene expression, which is useful in the treatment of chronic diseases. In most therapeutic applications, it is necessary to readminister the vector. This study characterizes the humoral immune response to AAV capsid proteins following intramuscular injection and its impact on vector readministration. Studies of mice and rhesus monkeys demonstrated the formation of neutralizing antibodies to AAV capsid proteins that persisted for over 1 year and then diminished, but this did not prevent the efficacy of vector readministration. More-detailed studies strongly suggested that the B-cell response was T cell dependent. This was further evaluated with a blocking antibody to human CD4, primatized for clinical trials, in a biologically compatible mouse in which the endogenous murine CD4 gene was functionally replaced with the human counterpart. Transient pharmacologic inhibition of CD4 T cells with CD4 antibody prevented an antivector response long after the effects of the CD4 antibody diminished; readministration of vector without diminution of gene expression was possible. Our studies suggest that truly durable transgene expression (i.e., prolonged genetic engraftment together with vector readministration) is possible with AAV in skeletal muscle, although it will be necessary to transiently inhibit CD4 T-cell function to avoid the activation of memory B cells.

Bench-scale anaerobic bioconversion of newsprint and office paper

Anaerobic bioconversion of newsprint and waste office paper was performed in bench-scale reactors with three inocula sources: landfill, rumen, and anaerobic digester. Office paper bioconversion was nearly complete within 20 days but continued for about 165 days with methane yield efficiencies ranging from 71-85% of potential chemical oxygen demand (COD) conversion. Average newsprint methane conversion efficiencies ranged from 32-41% of total COD under strictly anaerobic conditions for 300 days. Mass balance calculations revealed that more than 80% of newsprint cellulose was biodegraded. The apparent limiting factor for anaerobic bioconversion of newsprint was the physical association between lignin and cellulose. After proper acclimation, the three inocula tested equally well for methane production under strictly anaerobic conditions. Testing of ground, shredded strips, and whole paper pieces showed no effects of feedstock size on bioconversion rate or extent. Alkali pretreatment with NaOH concentration up to 10% significantly improved newsprint biodegradability. Treatment for longer duration or at elevated temperatures increased the solubilization of lignin, but did not improve bioconversion of newsprint to methane. Neutralizing treated samples with carbon dioxide gave higher methane yields compared to sulfuric or hydrochloric acids, suggesting that digester neutralization could be combined with biogas scrubbing.

Insertional mutagenesis of AAV2 capsid and the production of recombinant virus

The structural genes of adeno-associated virus serotype 2 (AAV2) have been altered by linker insertional mutagenesis in order to define critical components of virion assembly and infectivity. An in-frame restriction site linker was inserted across the capsid coding domain of a recombinant plasmid. After complementation in vivo, recombinant AAV2 viruses were generated and assayed for capsid production, packaging, transduction, heparin agarose binding, and morphology. Three classes of capsid mutants where identified. Class I mutants expressed structural proteins but were defective in virion assembly. Class II mutants generated intact virions that protected the viral genome from DNase, but failed to infect target cells. The majority of these mutants bound the heparin affinity matrix, suggesting that attachment to the AAV primary receptor was not rate limiting. One class II mutant, H2634, assembled virions and bound heparin using only Vp3, indicating that this subunit is responsible for mediating AAV receptor attachment. Finally, class III mutants assembled virions, encapsidated DNA, and infected target cells. Infectivity of these mutants ranged from 5 to 100% of that of the wild-type, demonstrating for the first time the ability to alter capsid proteins without interfering with infectivity. These AAV virions with altered capsid subunits will provide critical templates for manipulating AAV vectors for cell-specific gene delivery in vivo. In summary, the AAV capsid variants described here will facilitate further study of virus assembly, entry, and infection, as well as advance the development of this versatile vector system.

REV3 is required for spontaneous but not methylation damage-induced mutagenesis of Saccharomyces cerevisiae cells lacking O6-methylguanine DNA methyltransferase

O6-methylguanine (O6-MeG) DNA methyltransferase (MTase) removes the methyl group from a DNA lesion and directly restores DNA structure. It has been shown previously that bacterial and yeast cells lacking such MTase activity are not only sensitive to killing and mutagenesis by DNA methylating agents, but also exhibit an increased spontaneous mutation rate. In order to understand molecular mechanisms of endogenous DNA alkylation damage and its effects on mutagenesis, we determined the spontaneous mutational spectra of the SUP4-o gene in various Saccharomyces cerevisiae strains. To our surprise, the mgt1 mutant deficient in DNA repair MTase activity exhibited a significant increase in G:C-->C:G transversions instead of the expected G:C-->A:T transition. Its mutational distribution strongly resembles that of the rad52 mutant defective in DNA recombinational repair. The rad52 mutational spectrum has been shown to be dependent on a mutagenesis pathway mediated by REV3. We demonstrate here that the mgt1 mutational spectrum is also REV3-dependent and that the rev3 deletion offsets the increase of the spontaneous mutation rate seen in the mgt1 strains. These results indicate that the eukaryotic mutagenesis pathway is directly involved in cellular processing of endogenous DNA alkylation damage possibly by the translesion bypass of lesions at the cost of G:C-->C:G transversion mutations. However, the rev3 deletion does not affect methylation damage-induced killing and mutagenesis of the mgt1 mutant, suggesting that endogenous alkyl lesions may be different from O6-MeG.

Methionine reduces spontaneous and alkylation-induced mutagenesis in Saccharomyces cerevisiae cells deficient in O6-methylguanine-DNA methyltransferase

The exposure of DNA to reactive intracellular metabolites is thought to be a major cause of spontaneous mutagenesis. DNA alkylation is implicated in the above process by the fact that bacterial and yeast cells lacking DNA alkylation-specific repair genes exhibit elevated spontaneous mutation rates. The origin of the intracellular alkylating molecules is not clear; however, S-adenosylmethionine (SAM) has been proposed as one source because it has a reactive methyl group known to methylate proteins and DNA. We supplemented yeast cultures with excess methionine and examined the effects of increased endogenous SAM concentration on spontaneous and alkylation-induced mutagenesis in the absence of various DNA repair pathways. Our results show that either the excess methionine, or the increased SAM produced as a result of this treatment, is able to protect yeast cells from mutagenesis, and that this effect is alkylation-damage-specific. The protective effect was observed only in the mgt1 mutant deficient in the O(6)-methylguanine-DNA repair methyltransferase, but not in the wild type or other DNA repair-deficient strains, indicating that the protection is specific for O-methyl lesions. Thus, our results may lend support to the recently reported chemopreventive effect of SAM in rodents and further suggest that the observed tumor prevention by SAM may be, in part, due to its suppression of spontaneous mutagenesis in mammals. Given that a strong correlation has been established between O(6)-methylguanine and carcinogenicity, this study may offer a novel approach to preventing carcinogenesis.

Charge-to-alanine mutagenesis of the adeno-associated virus type 2 Rep78/68 proteins yields temperature-sensitive and magnesium-dependent variants

The adeno-associated virus type 2 (AAV) replication (Rep) proteins Rep78 and 68 (Rep78/68) exhibit a number of biochemical activities required for AAV replication, including specific binding to a 22-bp region of the terminal repeat, site-specific endonuclease activity, and helicase activity. Individual and clusters of charged amino acids were converted to alanines in an effort to generate a collection of conditionally defective Rep78/68 proteins. Rep78 variants were expressed in human 293 cells and analyzed for their ability to mediate replication of recombinant AAV vectors at various temperatures. The biochemical activities of Rep variants were further characterized in vitro by using Rep68 His-tagged proteins purified from bacteria. The results of these analyses identified a temperature-sensitive (ts) Rep protein (D40,42,44A-78) that exhibited a delayed replication phenotype at 32 degrees C, which exceeded wild-type activity by 48 h. Replication activity was reduced by more than threefold at 37 degrees C and was undetectable at 39 degrees C. Stability of the Rep78 protein paralleled replication levels at each temperature, further supporting a ts phenotype. Replication differences resulted in a 3-log-unit difference in virus yields between the permissive and nonpermissive temperatures (2.2 x 10(6) and 3 x 10(3), respectively), demonstrating that this is a relatively tight mutant. In addition to the ts Rep mutant, we identified a nonconditional mutant with a reduced ability to support viral replication in vivo. Additional characterization of this mutant demonstrated an Mg(2+)-dependent phenotype that was specific to Rep endonuclease activity and did not affect helicase activity. The two mutants described here are unique, in that Rep ts mutants have not previously been described and the D412A Rep mutant represents the first mutant in which the helicase and endonuclease functions can be distinguished biochemically. Further understanding of these mutants should facilitate our understanding of AAV replication and integration, as well as provide novel strategies for production of viral vectors.

Genetic interactions between error-prone and error-free postreplication repair pathways in Saccharomyces cerevisiae

Evidence obtained from recent studies supports the existence of an error-free postreplication repair (PRR) and a mutagenesis pathway within the Saccharomyces cerevisiae RAD6 DNA repair group. The MMS2 gene is the only known yeast gene involved in error-free PRR that, when mutated, significantly increases the spontaneous mutation rate. In this study, the mutational spectrum of the mms2 mutator was determined and compared to the wild type strain. In addition, mutagenenic effects and genetic interactions of the mms2 mutator and rev3 anti-mutator were examined with respect to forward mutations, frameshift reversions as well as amber and ochre suppressions. It was concluded from these results that the mms2 mutator phenotype is largely dependent on the functional REV3 gene. The synergistic effects of mms2 and rev3 mutations towards killing by a variety of DNA-damaging agents ruled out the possibility that MMS2 simply acts to suppress REV3 activity and favored the hypothesis that MMS2 and REV3 form two alternative subpathways within the RAD6 DNA repair pathway. Taken together, we propose that two pathways represented by MMS2 and REV3 deal with a similar range of endogenous and environmental DNA damage but with different biological consequences, namely, error-free repair and mutagenesis, respectively.

A piston model for transmembrane signaling of the aspartate receptor

To characterize the mechanism by which receptors propagate conformational changes across membranes, nitroxide spin labels were attached at strategic positions in the bacterial aspartate receptor. By collecting the electron paramagnetic resonance spectra of these labeled receptors in the presence and absence of the ligand aspartate, ligand binding was shown to generate an approximately 1 angstrom intrasubunit piston-type movement of one transmembrane helix downward relative to the other transmembrane helix. The receptor-associated phosphorylation cascade proteins CheA and CheW did not alter the ligand-induced movement. Because the piston movement is very small, the ability of receptors to produce large outcomes in response to stimuli is caused by the ability of the receptor-coupled enzymes to detect small changes in the conformation of the receptor.

Incorporation of an (125)I-labeled hexa-iodinated diglyceride analog into low-density lipoprotein and high specific uptake by cells of cervical carcinoma cell lines

The feasibility of using low-density lipoprotein (LDL) to deliver cytotoxic drugs to tumor cells has been explored since the 1980s, when cells of a number of cancer cell lines were found to have higher LDL receptor activity than normal cells. Such differential uptake between tumor and normal cells may provide a unique opportunity to use LDL as a tumor-specific carrier of radiopharmaceuticals for the clinical management of cancer. In this study, an (125)I-labeled hexa-iodinated diglyceride analog, 1, 3-dihydroxypropan-2-one 1,3-diiopanoate (DPIP), was synthesized and incorporated into LDL using a fusion technique. It was found that approximately 500 [(125)I] DPIP molecules were incorporated into each LDL particle. Cells of three human cervical tumor cell lines, HeLa, SiHa and C-33A, were used to examine the cellular uptake of the [(125)I]DPIP-LDL conjugate. It was shown that the [(125)I]DPIP-LDL conjugate was specifically bound to and taken up by cervical tumor cells through an LDL receptor-mediated endocytosis pathway. The results suggest that LDL may be a selective carrier for delivering hydrophobic radiopharmaceuticals to cancer cells and particularly for the diagnosis of cervical tumors.

Transduction of well-differentiated airway epithelium by recombinant adeno-associated virus is limited by vector entry

The limitations of adeno-associated virus (AAV)-mediated vectors for lung-directed gene transfer were investigated by using differentiated human respiratory epithelium in air-liquid interface cultures. Transduction efficiency was high in undifferentiated cells and was enhanced in well-differentiated cells after basolateral application of the vector or after apical application following disruption of tight junctions or pretreatment of the cultures with glycosidases. These results indicate that transduction of airway epithelia by AAV vectors is limited by entry and reinforce the importance of a physical barrier on the airway surface.

Formation of the yeast Mre11-Rad50-Xrs2 complex is correlated with DNA repair and telomere maintenance

The yeast Mre11 is a multi-functional protein and is known to form a protein complex with Rad50 and Xrs2. In order to elucidate the relationship between Mre11 complex formation and its mitotic functions, and to determine domain(s) required for Mre11 protein interactions, we performed yeast two-hybrid and functional analyses with respect to Mre11 DNA repair and telomere maintenance. Evidence presented in this study indicates that the N-terminal region of Mre11 constitutes the core homo-dimerization and hetero-dimerization domain and is sufficient for Mre11 DNA repair and maintaining the wild-type telomere length. In contrast, a stretch of 134 amino acids from the extreme C-terminus, although essential for achieving a full level of self-association, is not required for the aforementioned Mre11 mitotic functions. Interestingly, deletion of these same 134 amino acids enhanced the interaction of Mre11 with Rad50 and Xrs2, which is consistent with the notion that this region is specific for meiotic functions. While Mre11 self-association alone is insufficient to provide the above mitotic activities, our results are consistent with a strong correlation between Mre11-Rad50-Xrs2 complex formation, mitotic DNA repair and telomere maintenance. This correlation was further strengthened by analyzing two mre11 phosphoesterase motif mutants ( mre11-2 and rad58S ), which are defective in DNA repair, telomere maintenance and protein interactions, and a rad50S mutant, which is normal in both complex formation and mitotic functions. Together, these results support and extend a current model regarding Mre11 structure and functions in mitosis and meiosis.

Gene therapy vectors based on adeno-associated virus type 1

The complete sequence of adeno-associated virus type 1 (AAV-1) was defined. Its genome of 4,718 nucleotides demonstrates high homology with those of other AAV serotypes, including AAV-6, which appears to have arisen from homologous recombination between AAV-1 and AAV-2. Analysis of sera from nonhuman and human primates for neutralizing antibodies (NAB) against AAV-1 and AAV-2 revealed the following. (i) NAB to AAV-1 are more common than NAB to AAV-2 in nonhuman primates, while the reverse is true in humans; and (ii) sera from 36% of nonhuman primates neutralized AAV-1 but not AAV-2, while sera from 8% of humans neutralized AAV-2 but not AAV-1. An infectious clone of AAV-1 was isolated from a replicated monomer form, and vectors were created with AAV-2 inverted terminal repeats and AAV-1 Rep and Cap functions. Both AAV-1- and AAV-2-based vectors transduced murine liver and muscle in vivo; AAV-1 was more efficient for muscle, while AAV-2 transduced liver more efficiently. Strong NAB responses were detected for each vector administered to murine skeletal muscle; these responses prevented readministration of the same serotype but did not substantially cross-neutralize the other serotype. Similar results were observed in the context of liver-directed gene transfer, except for a significant, but incomplete, neutralization of AAV-1 from a previous treatment with AAV-2. Vectors based on AAV-1 may be preferred in some applications of human gene therapy.

Microemulsion of seal oil markedly enhances the transfer of a hydrophobic radiopharmaceutical into acetylated low density lipoprotein

Four different microemulsions differing in their core lipid component (triolein, canola oil, squalene, or seal oil) and containing 1,3-dihydroxypropan-2-one 1,3-diiopanoate (DPIP), a potential radioimaging probe, were prepared by means of ultrasonication. The DPIP microemulsions were incubated with acetylated human low density lipoprotein (AcLDL) and the amount of DPIP transferred into AcLDL was examined. The amount of DPIP in the microemulsions expressed as DPIP/oil (w/w) was dependent on the core lipid component of the microemulsion in the order of seal oil (0.19+/-0.04, mean +/- standard deviation) > squalene (0.15+/-0.02) > canola oil (0.12+/-0.02) > triolein (0.07+/-0.004). With the exception of canola oil, all microemulsions were effective in enhancing the transfer of DPIP into AcLDL in comparison with commonly used methods, i.e., direct diffusion and detergent solubilization. DPIP in seal oil resulted in the highest amount of DPIP transferred into AcLDL [309.16+/-34.82 vs. 203.19+/-64.51 using squalene and 151.31+/-28.54 using triolein (DPIP molecules per AcLDL particle)]. For the first time, oil from harp seals, was studied as a major core lipid component of formulating pharmaceutical microemulsions. DPIP in seal oil resulted in the highest transfer of DPIP into AcLDL which is likely due to the highest DPIP concentration found in this microemulsion as well as the high fluidity of seal oil.

2-5A-DNA conjugate inhibition of respiratory syncytial virus replication: effects of oligonucleotide structure modifications and RNA target site selection

To define more fully the conditions for 2-5A-antisense inhibition of respiratory syncytial virus (RSV), relationships between 2-5A antisense oligonucleotide structure and the choice of RNA target sites to inhibition of RSV replication have been explored. The lead 2-5A-antisense chimera for this study was the previously reported NIH8281 that targets the RSV M2 RNA. We have confirmed and extended the earlier study by showing that NIH8281 inhibited RSV strain A2 replication in a variety of antiviral assays, including virus yield reduction assays performed in monkey (EC90 = 0.02 microM) and human cells (EC90 = microM). This 2-5A-antisense chimera also inhibited other A strains, B strains and bovine RSV in cytopathic effect inhibition and Neutral Red Assays (EC50 values = 0.1-1.6 microM). The 2'-O-methylation modification of NIH8281 to increase affinity for the complementary RNA and provide nuclease resistance, the introduction of phosphothioate groups in the antisense backbone to enhance resistance to exo- and endonucleases, and the addition of cholesterol to the 3'-terminus of the antisense oligonucleotide to increase cellular uptake, all resulted in loss of activity. Of the antisense chimeras targeting other RSV mRNAs (NS1, NS2, P, M. G, F, and L), only those complementary to L mRNA were inhibitory. These results suggest that lower abundance mRNAs may be the best targets for 2-5A-antisense; moreover, the active 2-5A antisense chimeras in this study may serve as useful guides for the development of compounds with improved stability, uptake and anti-RSV activity.

Anisotropic Templating Effect in the Formation of Two-Dimensional Anionic Cadmium-Thiocyanate Coordination Solids [(12C4)(2)Cd][Cd(2)(SCN)(6)] and [(12C4)(2)Cd][Cd(3)(SCN)(8)] with Checkerboard and Herringbone Patterns, Respectively

This paper reports the syntheses, characterization, and structures of two new two-dimensional cadmium-thiocyanate coordination solids [(12C4)(2)Cd][Cd(2)(SCN)(6)] (1) and [(12C4)(2)Cd][Cd(3)(SCN)(8)] (2), where 12C4 denotes 12-crown-4, C(8)H(16)O(4). 1 crystallizes in a monoclinic unit cell, space group C2/c with lattice parameters a = 16.297(3) Å, b = 26.267(3) Å, c = 16.296(2) Å, beta = 90.20(1) degrees, and Z = 8. 2 crystallizes in a monoclinic unit cell, space group P2(1)/n with lattice parameters a = 11.604(7) Å, b = 11.366(7) Å, c = 15.736(4) Å, beta = 92.84(3) degrees, and Z = 2. The structure of 1 exhibits a two-dimensional tetragonal motif consisting of Cd(2) units arranged in a checkerboard pattern with the dimeric [Cd(2)(SCN)(6)](2)(-) complex as the building block. The crystal structure of 2 can be described as a two-dimensional hexagonal array of linear trimeric Cd(3) units arranged in a herringbone pattern with the [Cd(3)(SCN)(8)](2)(-) complex as the building block. In both 1 and 2, the [(12C4)(2)Cd](2+) dications are housed in cavities within and between the anionic cadmium-thiocyanate layers but with different orientations ("upright" in 1 and "sideways" in 2) with respect to the cadmium-thiocyanate layers, giving rise to an anisotropic templating effect.

Radiolabeled cholesteryl iopanoate/acetylated low density lipoprotein as a potential probe for visualization of early atherosclerotic lesions in rabbits

PURPOSE

Atherosclerosis is the underlying factor leading to such cardiovascular diseases (CVD) as stroke, aneurysm, and myocardial infarction. The early detection of atherosclerotic plaques is considered to be crucial for successful prevention and/or therapeutic and dietary intervention of CVD. Current diagnostic practice, on the other hand, can only detect the problem at an advanced stage. The purpose of this study was to examine the potential of using a radiolabeled cholesterol ester analog/acetylated low density lipoprotein (AcLDL) conjugate as a diagnostic agent for the early and non-invasive detection of atherosclerosis and for the monitoring of the effects of drug therapy.

METHODS

Cholesteryl iopanoate (CI), a cholesterylester analog, was synthesized, radiolabeled, and incorporated into AcLDL. Early atherosclerotic lesions were induced in New Zealand White rabbits. 125[-CI/AcLDL was injected intravenously at 2 microCi/kg. Blood samples were taken at different time intervals after injection and clearance of the injected drug from blood was studied. The rabbits were sacrificed after 72 hours and the distribution of radioactivity in various organs was investigated. Aortae of both atherosclerotic lesion and control rabbits were removed for Sudan IV staining and autoradiography in order to confirm the formation of the atherosclerotic lesion and localization of radioactivity.

RESULTS

The injected drug was found to be cleared from blood following a two compartment model. Radioactivity in the atherosclerotic aorta was found to be about 8 times higher than that in normal aorta, suggesting that the proposed diagnostic probe was selectively taken up by the atherosclerotic lesion. The autoradiography and staining confirmed that the localization of the proposed probe was superimposed with the atherosclerotic lesion site.

CONCLUSIONS

The results suggested that incorporation of CI into AcLDL resulted in the selective localization of CI at the atherosclerotic plaque areas. CI/AcLDL labeled with appropriate radioisotope has the potential to be used as a probe for visualization of early atherosclerotic lesion using scintigraphy technology.

Isolation of hMRE11B: failure to complement yeast mre11 defects due to species-specific protein interactions

The Saccharomyces cerevisiae MRE11 gene plays an important role in meiotic recombination, mitotic DNA repair and telomere maintenance. We present the isolation of hMRE11B cDNA from a human HeLa cell cDNA library as an MRE11 homolog. Compared to the previously identified hMRE11, hMRE11B contains an additional 84bp sequence that results in a 28 amino-acid insertion close to the C-terminus. The expression pattern of hMRE11B in different tissues shows the presence of two mRNA species of approx. 2.6 and 7.5kb. Overexpression of hMRE11B does not complement the alkylation sensitivity of the mre11 null and temperature-sensitive mutant strains. In this study, we examine factors that may explain this lack of complementation. First, both Northern and Western analyses rule out the lack of hMRE11B transcription and/or translation in yeast. Second, we demonstrate that hMre11B, like the yeast Mre11 protein, dimerizes in vivo in a yeast two-hybrid system. This dimerization requires the C-terminal one-third of hMre11B protein, which includes the 28 amino acids absent in hMre11. However, hMre11B does not interact with Mre11, Rad50 and Xrs2. Hence, the lack of protein-protein interaction between hMre11B and the yeast Mre11, Rad50, and Xrs2 may explain the inability of hMRE11B to complement the yeast mre11 mutants. We rule out the hypothesis that the lack of interaction and, in turn of complementation, is due to the absence of sequence homology at the C-terminal domain of hMre11B compared to the yeast Mre11. Instead, we propose that the C-terminus of hMre11B participates in protein-protein interaction and functions in a species-specific manner.

Adeno-associated virus as a vector for liver-directed gene therapy

Factors relevant to the successful application of adeno-associated virus (AAV) vectors for liver-directed gene therapy were evaluated. Vectors with different promoters driving expression of human alpha-1-antitrypsin (alpha-1AT) were injected into the portal circulation of immunodeficient mice. alpha-1AT expression was stable but dependent on the promoter. Southern analysis of liver DNA revealed approximately 0.1 to 2.0 provirus copies/diploid genome in presumed head-to-tail concatamers. In situ hybridization and immunohistochemical analysis revealed expression in approximately 5% of hepatocytes clustered in the pericentral region. These results support the use of AAV as a vector for diseases treatable by targeting of hepatocytes.

2',5'-Oligoadenylate-antisense chimeras cause RNase L to selectively degrade bcr/abl mRNA in chronic myelogenous leukemia cells

We report an RNA targeting strategy, which selectively degrades bcr/abl mRNA in chronic myelogenous leukemia (CML) cells. A 2', 5'-tetraadenylate activator (2-5A) of RNase L was chemically linked to oligonucleotide antisense directed against either the fusion site or against the translation start sequence in bcr/abl mRNA. Selective degradation of the targeted RNA sequences was demonstrated in assays with purified RNase L and decreases of p210(bcr/abl) kinase activity levels were obtained in the CML cell line, K562. Furthermore, the 2-5A-antisense chimeras suppressed growth of K562, while having substantially reduced effects on the promyelocytic leukemia cell line, HL60. Findings were extended to primary CML cells isolated from bone marrow of patients. The 2-5A-antisense treatments both suppressed proliferation of the leukemia cells and selectively depleted levels of bcr/abl mRNA without affecting levels of beta-actin mRNA, determined by reverse transcriptase-polymerase chain reaction (RT-PCR). The specificity of this approach was further shown with control oligonucleotides, such as chimeras containing an inactive dimeric form of 2-5A, antisense lacking 2-5A, or chimeras with altered sequences including several mismatched nucleotides. The control oligonucleotides had either reduced or no effect on CML cell growth and bcr/abl mRNA levels. These findings show that CML cell growth can be selectively suppressed by targeting bcr/abl mRNA with 2-5A-antisense for decay by RNase L and suggest that these compounds should be further explored for their potential as ex vivo purging agents of autologous hematopoietic stem cell transplants from CML patients.

Differential regulation of two closely clustered yeast genes, MAG1 and DDI1, by cell-cycle checkpoints

Eukaryotic DNA-damage checkpoint genes have been shown to not only arrest cells at certain stages, but are also involved in the transcriptional response to DNA damage. However, while the signal transduction for cell-cycle checkpoint is well characterized, it is not clear whether the same signal transduction pathway is responsible for the regulation of all DNA damage-inducible genes. In order to understand how different checkpoint genes are involved in gene regulation, the effects of various checkpoint mutations on the expression of a unique yeast MAG1 - DDI1 dual promoter were examined in this study. MAG1 and DDI1 are transcribed from a common promoter region and co-induced by a variety of DNA damaging agents. However, gene-specific cis -acting elements were also identified, and the two genes are indeed differentially expressed under certain conditions. We found that DDI1 induction was not affected in any of the checkpoint mutants. In contrast, MAG1 induction was completely abolished in the pol2 and rad53 mutants. However, in the mec1-1 or any of the G1/S and G2/M checkpoint mutants, including rad9, rad17 and rad24, DNA damage-induced MAG1 expression was not significantly affected, and a rad9 rad17 double mutation only slightly reduced MAG1 induction. Based on this and previous studies, we present two models for the role of checkpoint genes in transcriptional regulation in response to DNA damage.

Molecular cloning and genetic characterization of the Saccharomyces cerevisiae NGS1/MRE11 gene

The Saccharomyces cerevisiae ngs1-1 mutant was previously identified by its enhanced sensitivity to simple DNA-alkylating agents such as methyl methanesulfonate but not to UV. Molecular cloning and sequencing of NGS1 as a putative DNA-alkylation repair gene revealed that it isidentical to MRE11, a gene that is involved in DNA recombinational repair. In order to investigate functional domains of the Mre11 protein, nucleotide-sequence alterations of a number of mre11 mutant alleles, including ngs1-1, mre11-1 (ts), mre11-2, mre11-3 and mre11-58, were determined. Most of these mutations map to the N-terminus ofMre11, emphasizing the importance of this highly conserved domain. The ngs1-1 and mre11-3 mutants carry nonsense mutations resulting in truncated proteins. Missense mutations were found in mre11-1 (ts), mre11-2 and mre11-58, of which mre11-2 and mre11-58 mapped to the conserved phosphoesterase domains, indicating the involvement of these motifs in the formation and/or processing of DNA double-strand breaks. Finally, mitotic-recombination assays show that the mre11 delta mutation enhances inter-chromosomal recombination but decreases the intra-chromosomal deletion frequency. In addition, MRE11 appears to play different roles during spontaneous and alkylation-induced homologous mitotic recombination.

High-titer adeno-associated viral vectors from a Rep/Cap cell line and hybrid shuttle virus

Adeno-associated virus (AAV) is a potential vector for in vivo gene therapy. A critical analysis of its utility has been hampered by methods of production that are inefficient, difficult to scale up, and that often generate substantial quantities of replication-competent AAV. We describe a novel method for producing AAV that addresses these problems. A cell line, called B50, was created by stably transfecting into HeLa cells a rep/cap-containing plasmid utilizing endogenous AAV promoters. Production of AAV occurs in a two-step process. B50 is infected with an adenovirus defective in E2b, to induce Rep and Cap expression and provide helper functions, followed by a hybrid virus in which the AAV vector is cloned in the E1 region of a replication-defective adenovirus. This results in a 100-fold amplification and rescue of the AAV genome, leading to a high yield of recombinant AAV that is free of replication-competent AAV. Intramuscular injection of vector encoding erythropoietin into skeletal muscle of mice resulted in supraphysiologic levels of hormone in serum that was sustained and caused polycythemia. This method of AAV production should be useful in scaling up for studies in large animals, including humans.