Adeno-associated virus serotype 2-mediated gene transfer to the parotid glands of nonhuman primates

Salivary glands (SGs) are promising gene transfer targets with potential clinical applicability. Previous experiments in rodents using recombinant serotype 2 adeno-associated viral (rAAV2) vectors have demonstrated relatively stable transgene-encoded protein levels after SG gene transfer. In the present study, we examine direct SG administration of rAAV2 vectors encoding rhesus macaque erythropoietin (RhEPO) to the parotid glands of nonhuman primates using two different doses (n = 3 per group; 1 x 10(10) or 3 x 10(11) particles/gland, respectively). Gene transfer had no negative effects on general macaque physiology (e.g., weight, complete blood count, and serum chemistry). Macaques were euthanized 6 months after vector administration and complete necropsy and pathology assessments were performed, revealing no vector-related pathological lesions in any of the examined organs. In the high-dose group, RhEPO expression increased quickly (i.e., by week 1) and levels remained relatively stable both in serum and saliva until the end of the study. Serum-to-saliva ratios of RhEPO revealed secretion of the transgene product into the bloodstream, but not to the extent previously observed in mice. Furthermore, the kinetic results were not predicted by those observed in murine SGs. With respect to viral biodistribution, at necropsy vector was found overwhelmingly in the targeted parotid gland ( approximately 100 times more than levels in other tissues, most of which were similar to tissue levels in nontreated animals). We conclude that administration of modest doses of rAAV2 vectors to SGs for therapeutic purposes can be accomplished without significant or permanent injury to the targeted gland or to distant organs of nonhuman primates.

USER friendly DNA engineering and cloning method by uracil excision

Here we report a PCR-based DNA engineering technique for seamless assembly of recombinant molecules from multiple components. We create cloning vector and target molecules flanked with compatible single-stranded (ss) extensions. The vector contains a cassette with two inversely oriented nicking endonuclease sites separated by restriction endonuclease site(s). The spacer sequences between the nicking and restriction sites are tailored to create ss extensions of custom sequence. The vector is then linearized by digestion with nicking and restriction endonucleases. To generate target molecules, a single deoxyuridine (dU) residue is placed 6-10 nt away from the 5'-end of each PCR primer. 5' of dU the primer sequence is compatible either with an ss extension on the vector or with the ss extension of the next-in-line PCR product. After amplification, the dU is excised from the PCR products with the USER enzyme leaving PCR products flanked by 3' ss extensions. When mixed together, the linearized vector and PCR products directionally assemble into a recombinant molecule through complementary ss extensions. By varying the design of the PCR primers, the protocol is easily adapted to perform one or more simultaneous DNA manipulations such as directional cloning, site-specific mutagenesis, sequence insertion or deletion and sequence assembly.

Histone-mediated transduction as an efficient means for gene delivery

Gene delivery into the nucleus of eukaryotic cells is inefficient, largely because of the significant barriers within the target cell of the plasma membrane and nuclear envelope. Recently, a group of basic proteins, including the HIV-1 Tat protein and the four core histones, have been shown to enter cells through a novel energy- and receptor-independent manner. Here, we show that engineered histone H2B proteins are able to mediate the efficient delivery of either green fluorescent protein or DNA into HeLa cells through the process of "Histone-Mediated Transduction" (HMT), with further enhancement achieved by utilizing a dimer of histones H2B and H2A. Subsequent nuclear delivery was accelerated approximately two-fold by the addition of an optimized nuclear localization signal to histone H2B, thereby increasing the affinity of interaction with components of the cellular nuclear import machinery, resulting in increased expression of a reporter gene. Further, we demonstrate that the domains responsible for this histone transduction are located in the N-terminal tail and globular regions of histone H2B. HMT represents a new, efficient, and technically non-demanding means to deliver DNA to the nucleus of intact cells, including embryonic stem cells, which has important applications in gene therapy and cancer therapeutics.

Characterization of the ColE2-like replicon of plasmid pTT8 from Thermus thermophilus

We identified the 1.6-kb region of Thermus thermophilus plasmid pTT8 capable of autonomous replication, which shows a significant sequence similarity to the replicon regions of the ColE2-related plasmids. We showed the requirement of DNA polymerase I for pTT8 replication. The putative rep gene coding for the replication initiator protein, Rep, similar to those of the ColE2-related plasmids was cloned into an expression vector. The 6xHis-Rep protein expressed in Escherichia coli was successfully purified by stepwise denaturing with urea and refolding in the presence of glycerol on Ni-resin. We identified the nucleotide sequence recognized by the pTT8 Rep protein by the SELEX experiment using the purified protein, and proposed the existence of the third origin of pTT8 replication different from those predicted previously.

Gene manipulation of fluorescent protein through site-selective hydrolysis by Ce(IV)/EDTA

Previously we reported that gap-site, formed in substrate DNA by using two oligonucleotide additives, was selectively hydrolyzed by Ce(IV)/EDTA. Herein this site-selective scission was used for gene manipulation, and green fluorescent protein (GFP) was converted to blue fluorescent protein (BFP). The sense strand of GFP was cleaved at predetermined site by using this system, and its upstream fragment was connected with the downstream of BFP gene by T4 DNA ligase. In this manipulation, three amino acid residues in GFP (C at the position 65, Y at 66, and T at 167) were converted to S, H, and I, respectively. The sequencing experiment confirmed that desired recombinant DNA was prepared, and the recombinant DNA was successfully expressed to emit blue fluorescence.

Isoform-specific early trafficking of AMPA receptor flip and flop variants

Flip and flop splice variants of AMPA receptor subunits are expressed in distinct but partly overlapping patterns and impart different desensitization kinetics to cognate receptor channels. In the absence of specific antibodies, isoform-specific differences in trafficking or localization of native flip and flop subunits remain uncharacterized. We report that in several transfected cell lines, transport of homomeric glutamate receptor (GluR)-D(flop) receptors is largely blocked at the endoplasmic reticulum (ER) exit, whereas GluR-D(flip) undergoes complex glycosylation and reaches the plasma membrane at >10x higher levels than GluR-D(flop), as determined by immunofluorescence, patch-clamp recordings and biochemical assays. The transport difference between flip and flop is independent of activity, is primarily determined by amino acid residue 780 (Leu in flop, Val in flip), and is manifested even in the secretion of the soluble ligand-binding domain, suggesting it is independent of oligomerization. Coexpression with stargazin or with the flip isoform rescues the surface expression of GluR-D(flop) near to the level exhibited by GluR-D(flip). Our results demonstrate that the extracellular flip/flop region, via interactions with ER luminal splice form-specific protein(s), plays a hitherto unappreciated and important role in AMPA-receptor trafficking.

[Analysis of in vitro delivering CD8+ T epitopes by attenuated bacteria]

AIM

To analyze the efficiency of delivery for CD8(+) T cell epitopes by recombinant bacteria vectors.

METHODS

The recombinant E. coli strain 13A or 25A and recombinant Salmonella typhimurium strain SL7207 expressing CD8(+) T cell epitopes of Lymphocytic Choriomeningitis Virus (LCMV) and Ovalbumin (OVA), which were fused with green fluorescent protein (GFP) marker at the C-terminal, were infected into LK(b) cells, LL(d) cells or bone marrow dendritic cells (BMDC). The efficiency of presentation for CD8(+) T cell epitopes by recombinant bacteria was analyzed by in vitro antigen presentation assay.

RESULTS

After the infection of LK(b) cells, LL(d) cells or BMDC by recombinant bacteria, about 90% of cells were GFP positive. The results indicated that attenuated strain 13A, 25A and SL7207 had better invasive capacity to LK(b) and LL(d) cells, while BMDC had stronger capacity for uptaking recombinant bacteria. At 2 h post infection, CD8(+) T cell epitopes presented on the surface of those LK(b), LL(d) and BMDC cells infected by 13A (ptG2F) and SL7207(ptG2F) could be recognized by B3Z or nV1H7 T hybridoma cells, which were specific for OVA peptide p257-264 or LCMV peptide p118-132, respectively. But the efficiency of presentation for OVA or LCMV CD8(+) T cell epitope was decreased or increased respectively at 48 h post infection. However, LK(b), LL(d) and BMDC cells infected by 25A (ptG2F) did not effectively stimulate the specific B3Z or nV1H7 T cells. Furthermore, the presentation efficiency of BMDC was higher than those of LK(b) and LL(d) cells under the same condition.

CONCLUSION

CD8(+) T cell epitopes can be delivered and presented to T lymphocytes by APC by attenuated bacteria in vitro.

Rat bone marrow progenitor cells transduced in situ by rSV40 vectors differentiate into multiple central nervous system cell lineages

Using bone marrow-directed gene transfer, we tested whether bone marrow-derived cells may function as progenitors of central nervous system (CNS) cells in adult animals. SV40-derived gene delivery vectors were injected directly into femoral bone marrow, and we examined transgene expression in blood and brain for 0-16 months thereafter by immunostaining for FLAG epitope marker. An average of 5% of peripheral blood cells and 25% of femoral marrow cells were FLAG(+) throughout the study. CNS FLAG-expressing cells were mainly detected in the dentate gyrus (DG) and periventricular subependymal zone (PSZ). Although absent before 1 month and rare at 4 months, DG and PSZ FLAG(+) cells were abundant 16 months after bone marrow injection. Approximately 5% of DG cells expressed FLAG, including neurons (48.6%) and microglia (49.7%), and occasional astrocytes (1.6%), as determined by double immunostaining for FLAG and lineage markers. These data suggest that one or more populations of cells resident within adult bone marrow can migrate to the brain and differentiate into CNS-specific cells.

Quantitative determination of free-DNA uptake in river bacteria at the single-cell level by in situ rolling-circle amplification

Detection of plasmid DNA uptake in river bacteria at the single-cell level was carried out by rolling-circle amplification (RCA). Uptake of a plasmid containing the green fluorescent protein gene (gfp) by indigenous bacteria from two rivers in Osaka, Japan, was monitored for 506 h using this in situ gene amplification technique with optimized cell permeabilization conditions. Plasmid uptake determined by in situ RCA was compared to direct counts of cells expressing gfp under fluorescence microscopy to examine differences in detection sensitivities between the two methods. Detection of DNA uptake as monitored by in situ RCA was 20 times higher at maximum than that by direct counting of gfp-expressing cells. In situ RCA could detect bacteria taking up the plasmid in several samples in which no gfp-expressing cells were apparent, indicating that in situ gene amplification techniques can be used to determine accurate rates of extracellular DNA uptake by indigenous bacteria in aquatic environments.

Rapid specific amplification of rat antibody cDNA from nine hybridomas in the presence of myeloma light chains

Most monoclonal antibodies to mouse antigens have been derived from rat spleen-mouse myeloma fusions. Many resultant hybridomas express one of several myeloma kappa chain transcripts, even though the parent myeloma may have been ascribed as not expressing light chain protein. Previous reports have only differentiated against one of these mouse light chains. We have found at least three different myeloma kappa transcripts in the panel of nine hybridomas that were derived from four different myeloma parents. We have designed an amplification strategy that differentiates the rearranged rat kappa chain from all mouse light chains. Moreover, this method is expedient as it requires minimal downstream manipulation.

Metabolome, transcriptome, and bioinformatic cis-element analyses point to HNF-4 as a central regulator of gene expression during enterocyte differentiation

DNA-binding transcription factors bind to promoters that carry their binding sites. Transcription factors therefore function as nodes in gene regulatory networks. In the present work we used a bioinformatic approach to search for transcription factors that might function as nodes in gene regulatory networks during the differentiation of the small intestinal epithelial cell. In addition we have searched for connections between transcription factors and the villus metabolome. Transcriptome data were generated from mouse small intestinal villus, crypt, and fetal intestinal epithelial cells. Metabolome data were generated from crypt and villus cells. Our results show that genes that are upregulated during fetal to adult and crypt to villus differentiation have an overrepresentation of potential hepatocyte nuclear factor (HNF)-4 binding sites in their promoters. Moreover, metabolome analyses by magic angle spinning (1)H nuclear magnetic resonance spectroscopy showed that the villus epithelial cells contain higher concentrations of lipid carbon chains than the crypt cells. These findings suggest a model where the HNF-4 transcription factor influences the villus metabolome by regulating genes that are involved in lipid metabolism. Our approach also identifies transcription factors of importance for crypt functions such as DNA replication (E2F) and stem cell maintenance (c-Myc).

Screening for inter-individual splicing differences in human GSTM4 and the discovery of a single nucleotide substitution related to the tandem skipping of two exons

The glutathione S-transferase Mu class (GSTM) genes encode phase II metabolism enzymes that are involved in the detoxification of various carcinogens and drugs. Some genetic polymorphisms in GSTM genes are related to disease phenotypes and drug-metabolism differences in the population. Polymorphisms that alter gene-splicing patterns are functionally very important because they often lead to the insertion or deletion of many amino acids. To identify inter-individual differences in the splicing pattern of the GSTM4 gene, we used reverse transcriptase polymerase chain reaction (RT-PCR) to screen cDNA from 96 human liver samples. We discovered a novel splice variant of GSTM4 that resulted from tandem skipping of exons 4 and 5. This exon-skipping event is associated with a mutation at the splice acceptor site in intron 4.

Structure function and splice site analysis of the synaptogenic activity of the neurexin-1 beta LNS domain

Recent findings suggest that the neurexin-neuroligin link promotes both GABAergic and glutamatergic synaptogenesis, but the mechanism by which neurexins influence the clustering of appropriate neuroligins and postsynaptic differentiation remains unclear. Previous studies suggested that the presence or absence of alternatively spliced residues at splice site 4 (S4) in the neurexin LNS domain may regulate neurexin function. We demonstrate that addition of the S4 insert selectively reduces the ability of neurexin-1beta to cluster neuroligin-1/3/4 and glutamatergic postsynaptic proteins, although clustering of neuroligin-2 and GABAergic postsynaptic proteins remain strong. Furthermore, addition of the S4 insert decreases the binding affinity of neurexin-1beta to neuroligins-1 and -4 but has little effect on binding to neuroligins-2 and -3. Additional structure-function studies reveal the neurexin binding interface mediating synaptogenic activity to be composed primarily of residues in the beta2beta3, beta6beta7, and beta10beta11 loops on one rim of the LNS domain beta sandwich. Mutation of two predicted Ca(2+)-binding residues disrupts postsynaptic protein clustering and binding to neuroligins, consistent with previous findings that neurexin-neuroligin binding is Ca2+ dependent. Glutamatergic postsynaptic clustering was more readily disrupted by the mutagenesis than GABAergic postsynaptic protein clustering. Perhaps neurexins-neuroligins, or neurexin-1beta at least, is most important for GABA synapse formation or controlling the balance of GABA and glutamate synapses. These results suggest that differential neurexin-neuroligin binding affinities and splice variations may play an instructive role in postsynaptic differentiation.

Inhibition of human tyrosyl-DNA phosphodiesterase by aminoglycoside antibiotics and ribosome inhibitors

DNA topoisomerase I (Top1) is the target of camptothecin, and novel Top1 inhibitors are in development as anticancer agents. Top1 inhibitors damage DNA by trapping covalent complexes between the Top1 catalytic tyrosine and the 3'-end of the broken DNA. Tyrosyl-DNA phosphodiesterase (Tdp1) can repair Top1-DNA covalent complexes by hydrolyzing the tyrosyl-DNA bond. Inhibiting Tdp1 has the potential to enhance the anticancer activity of Top1 inhibitors (http://discover.nci.nih.gov/pommier/pommier.htm) and to act as antiproliferative agents. In the present study, we report that neomycin inhibits Tdp1 more effectively than the related aminoglycosides paromomycin and lividomycin A. Inhibition of Tdp1 by neomycin is observed both with single- and double-stranded substrates but is slightly stronger with duplex DNA, which is different from aclarubicin, which only inhibits Tdp1 with the double-stranded substrate. Inhibition by neomycin can be overcome with excess Tdp1 and is greatest at low pH. To our knowledge, aminoglycoside antibiotics and the ribosome inhibitors thiostrepton, clindamycin-2-phosphate, and puromycin are the first reported pharmacological Tdp1 inhibitors.

A pharmacological model for psychosis based on N-methyl-D-aspartate receptor hypofunction: molecular, cellular, functional and behavioral abnormalities

BACKGROUND

The psychotomimetic effects of N-methyl-D-aspartate (NMDA) receptor antagonists such as phencyclidine (PCP) in healthy humans and their ability to exacerbate psychotic symptoms in schizophrenic patients have promoted a view of schizophrenia as being related to altered glutamatergic neurotransmission.

METHODS

This prompted us and others to develop animal models for psychosis based on a glutamatergic approach. Pharmacological induction of a state of impaired glutamatergic neurotransmission based on chronic, low-dose application of MK-801, a highly selective noncompetitive NMDA antagonist, revealed marked parallels between schizophrenia and our animal model.

RESULTS

MK-801 altered the expression of NR1 splice variants and NR2 subunits of the NMDA receptor in a pattern partially resembling the alterations detected in schizophrenia. Ultrastructurally, the number of gamma-aminobutyric-acid (GABA)ergic parvalbumin-positive interneurons was relatively decreased, a finding which again parallels observations in post mortem brain from schizophrenic patients. As a functional consequence, local inhibition of pyramidal cells which is largely mediated by recurrent axon collaterals, originating from GABAergic interneurons, was altered. Not unexpectedly, these animals showed cognitive deficits resembling findings in schizophrenic humans.

CONCLUSIONS

These convergent lines of evidence suggest that our approach has a significant potential of serving as a model of the pathobiology of several aspects of psychosis and consequently could contribute to the development of new therapeutic strategies.

Oncolytic viruses derived from the gamma34.5-deleted herpes simplex virus recombinant R3616 encode a truncated UL3 protein

Replication-competent herpes simplex virus (HSV-1) mutants are used in clinical trials in the experimental treatment of cancer. Mutants G207, HSV1716, NV1020, and Oncovex GM-CSF share in common a defect in one or both copies of the gene encoding the neurovirulence factor, ICP34.5, and are thus neuroattenuated. These viruses are acknowledged to differ from one another (a) in the specific types of mutations intentionally introduced during their derivation and (b) in the inherent genetic differences retained from the different parent strains used in their construction. Unintended mutations are expected to emerge at some low frequency during the selection for and passage of mutant viruses. Here we demonstrate that during the construction of the oncolytic virus R3616, a nonsense mutation arose in an untargeted region of the HSV-1 genome that resulted in a substantial truncation of the viral protein known as UL3. This report is the first published documentation that oncolytic herpesviruses developed and used in clinical trials contain adventitious mutations. The implications of these findings for the characterization and development of vectors proposed for use in clinical trials are discussed.

Determination of the binding affinities of plasmid DNA using fluorescent intercalators possessing an acridine skeleton

Novel acridine derivatives, wherein the steric factor has been varied systematically through substitution at the 9 position of the acridine ring, were evaluated as convenient fluorescent probes for nucleic acid detection. The binding affinities of N-(9-acridinylthiocarbamoyl)amino acids (ATA) with plasmid DNA (pUC 19) were investigated using UV-vis spectrophotometry, fluorometric titration and quantum chemical calculations (AM1). From spectrofluorometric analysis, the binding constants for the DNA-ATA complexes were determined. To elucidate its DNA intercalation, the most preferable tautomeric structure of ATA was established by means of AM1 calculations.

Recombinant ??-Conotoxin MVIIA Possesses Strong Analgesic Activity

BACKGROUND

omega-Conotoxin (CTX) MVIIA is a specific antagonist of N-type voltage-sensitive calcium channels. A synthetic peptide version of CTX MVIIA (ziconotide) has been approved by the US FDA for severe and chronic pain. Given the high cost and complexity of the synthetic process of the disulfide-rich peptide, the genetic recombinant approach may simplify the development of this potent therapeutic agent.

AIM

In this study, we report a new method for production of the recombinant CTX MVIIA.

METHOD

A novel DNA fragment encoding CTX MVIIA was designed using Escherichia coli-preferred codons, and the fragment was cloned into the expression vector pGEX(2T). The fusion protein, CTX MVIIA and glutathione-S-transferase (GST) [GST-CTX MVIIA], was expressed in E. coli and purified by affinity chromatography on a glutathione-agarose column. After digestion with thrombin, the CTX MVIIA fragment was purified on a Sephacryl S-100 HR column and identified by mass spectrometry. The bioactivity of the peptide was evaluated by the hot tail-flick assay, in which the CTX MVIIA was intracerebroventricularly administered into Sprague-Dawley rats and its antinociceptive effect measured.

RESULTS

The analgesic activity of the conotoxin was about 800 times stronger than that of morphine.

CONCLUSION

The recombinant CTX MVIIA expressed in E. coli has shown marked analgesic activity, which may have potential in clinical application.

Minicircle DNA immobilized in bacterial ghosts: in vivo production of safe non-viral DNA delivery vehicles

DNA as an active agent is among the most promising technologies for vaccination and therapy. However, plasmid backbone sequences needed for the production of pDNA in bacteria are dispensable, reduce the efficiency of the DNA agent and, most importantly, represent a biological safety risk. In this report we describe a novel technique where a site-specific recombination system based on the ParA resolvase was applied to a self-immobilizing plasmid system (SIP). In addition, this system was combined with the protein E-specific lysis technology to produce non-living bacterial carrier vehicles loaded with minicircle DNA. The in vivo recombination process completely divided an origin plasmid into a minicircle and a miniplasmid. The replicative miniplasmid containing the origin of replication and the antibiotic resistance gene was lost during the subsequently induced PhiX174 gene E-mediated lysis process, which results in bacterial ghosts. The minicircle DNA was retained in these empty bacterial cell envelopes during the lysis process via the specific interaction of a membrane anchored protein with the minicircle DNA. Using this novel platform technology, a DNA delivery vehicle--consisting of a safe bacterial carrier with known adjuvant properties and minicircle DNA with an optimized safety profile--can be produced in vivo in a continuous process. Furthermore, this study provides the basis for the development of an efficient in vitro minicircle purification process.

Impairment of IGF-I gene splicing and MGF expression associated with muscle wasting

An aminopeptidase was purified from bovine skeletal muscle by ammonium sulfate fractionation and by successive chromatographies of DEAE-cellulose, Sehacryl S-200, phenyl-sepharose CL-4B, hydroxyapatite and Hi-Trap chelating HP columns. The aminopeptidase was purified about 14-fold over the crude extract with a yield of 1.0% activity. The molecular mass of the enzyme was found to be 58 kDa on SDS-PAGE. The enzyme activity was enhanced by the addition of some anions, such as Cl(-), NO(3)(-) and SCN(-), which is the most unique property of this enzyme. While, the activity was strongly inhibited by bestatin, PMSF and puromycin, suggesting that it was a serine protease. In addition, this enzyme was identical with leukotriene (LT) A4 hydrolase, converting LTA4 to LTB4.

Nucleoporins NPP-1, NPP-3, NPP-4, NPP-11 and NPP-13 are required for proper spindle orientation in C. elegans

Nucleoporins are components of the nuclear pore, which is required for nucleo-cytoplasmic transport. We report a role for a subclass of nucleoporins in orienting the mitotic spindle in C. elegans embryos. RNAi-mediated depletion of any of five putative nucleoporins npp-1, npp-3, npp-4, npp-11, and npp-13 leads to indistinguishable spindle orientation defects. Transgenic worms expressing NPP-1::GFP or NPP-11::GFP show GFP localization at the nuclear envelope, consistent with their predicted function. NPP-1 interacts with the other nucleoporins in yeast two-hybrid assays, suggesting that the proteins affect spindle orientation by a common process. The failed orientation phenotype of npp-1(RNAi) is at least partially epistatic to the ectopic spindle rotation in the AB blastomere of par-3 mutant embryos. This suggests that NPP-1 contributes to the mechanics of spindle orientation. However, NPP-1 is also required for PAR-6 asymmetry at the two-cell stage, indicating that nucleoporins may be required to define cortical domains in the germ line blastomere P1. Nuclear envelope structure is abnormal in npp-1(RNAi) embryos, but the envelope maintains its integrity, and most nuclear proteins we assayed accumulate normally. These findings raise the possibility that these nucleoporins may have direct roles in orienting the mitotic spindle and the maintenance of cell polarity.

Saving the ends for last: the role of pol mu in DNA end joining

At least three DNA polymerases participate in nonhomologous end joining in mammalian cells: pol mu, pol kappa, and TdT. A study in this issue of Molecular Cell (Nick McElhinny et al., 2005) clarifies the role of pol mu in end joining at the kappa light chain locus and also provides a biochemical explanation for the unique polymerization functions of pol mu on DNA ends.

Bacterial transfer of large functional genomic DNA into human cells

Efficient transfer of chromosome-based vectors into mammalian cells is difficult, mostly due to their large size. Using a genetically engineered invasive Escherichia coli vector, alpha satellite DNA cloned in P1-based artificial chromosome was stably delivered into the HT1080 cell line and efficiently generated human artificial chromosomes de novo. Similarly, a large genomic cystic fibrosis transmembrane conductance regulator (CFTR) construct of 160 kb containing a portion of the CFTR gene was stably propagated in the bacterial vector and transferred into HT1080 cells where it was transcribed, and correctly spliced, indicating transfer of an intact and functional locus of at least 80 kb. These results demonstrate that bacteria allow the cloning, propagation and transfer of large intact and functional genomic DNA fragments and their subsequent direct delivery into cells for functional analysis. Such an approach opens new perspectives for gene therapy.

Constitutive expression and localization of cytochrome P‐450 1A1 in rat and human brain: presence of a splice variant form in human brain 1

Cytochrome P-450 function as mono-oxygenases and metabolize xenobiotics. CYP1A1, a cytochrome P-450 enzyme, bioactivates polycyclic aromatic hydrocarbons to reactive metabolite(s) that bind to DNA and initiate carcinogenesis. Northern and immunoblot analyses revealed constitutive expression of Cyp1a1 and CYP1A1 in rat and human brain, respectively. CYP1A1 mRNA and protein were localized predominantly in neurons of cerebral cortex, Purkinje and granule cell layers of cerebellum and pyramidal neurons of CA1, CA2, and CA3 subfields of the hippocampus. RT-PCR analyses using RNA obtained from autopsy human brain samples demonstrated the presence of a splice variant having a deletion of 87 bp of exon 6. This splice variant was present in human brain, but not in the liver from the same individual, and was absent in rat brain and liver. Structural modeling indicated broadening of the substrate access channel in the brain variant. The study demonstrates the presence of a unique cytochrome P-450 enzyme in human brain that is generated by alternate splicing. The presence of distinct cytochrome P-450 enzymes in human brain that are different from well-characterized hepatic forms indicates that metabolism of xenobiotics including drugs could occur in brain by pathways different from those known to occur in liver.