Study of rat neuronal genes with ordered differential display method

Ordered differential display (ODD) was developed recently and has been applied to systematic comparison of expression profiles of genes. It was further improved with the specific complexing property between biotin and streptavidin by the authors. First, random primer and biotinylated oligo (dT) primer were used to make pools of double strand cDNA. Second, streptavidin-coated PCR tube is used to absorb 3'ESTs specifically to avoid the negative effect of other DNA fragments. In the case of 3'ESTs comparison patterns between embryonic brain and body of SD rat, more than forty differentially expressed genes were cloned and identified. The function of rZIC gene, one of the genes identified and cloned, was studied through ethological experiments. The result showed that rZIC gene was associated with locomotion activity of adult mice.

Overexpression, refolding, purification of Erbin PDZ domain from Escherichia coli and preparation of its polyclonal antibody

The Erbin was recently identified. The antibody against Erbin has not been commercially available. As a new member of peripheral protein LAP family and novel type of adaptor protein, its functions and binding partners are not completely known. In the present study, cDNA encoding PDZ domain of Erbin was inserted in a prokaryotic expression vector. His-tagged recombinant protein was overproduced in E. coli and purified by Ni-NTA column chromatography. About 14.4 mg of the purified protein was obtained from 500 mL of cell culture. The purity of the recombinant protein was higher than 90%. The polyclonal antibody against this protein was raised. The antibody can recognize both denatured and natural Erbin protein. It will be used to further identify the new binding partners of Erbin and study its unknown functions.

Blockade of micro-opioid receptors in the medial thalamus inhibits acquisition, but not expression, of morphine-induced conditioned place preference

The medial thalamus contains abundant mu-opioid receptors and is activated by acute morphine administration. However, the role of the medial thalamus in the rewarding effects of morphine is unclear. The present study examined whether mu-opioid receptors of the medial thalamus influenced the acquisition and expression of morphine-induced conditioned place preference (CPP) in rats. An unbiased apparatus and biased subject assignment were used. Administration of morphine in increasing doses (2 mg/kg, 4 mg/kg, 6 mg/kg, 10 mg/kg, s.c.) was paired with an initially non-preferred chamber and saline administration was paired with an initially preferred chamber. Conditioning trials were conducted twice daily for 4 days. Microinjection of the irreversible mu-opioid receptor antagonist, beta-funaltrexamine (5 microg/rat), into the medial thalamus 23 h prior to each morphine conditioning completely blocked the acquisition of CPP. However, microinjection of beta-funaltrexamine into the medial thalamus after morphine conditioning trials, but 23 h prior to a test session, had no effect on the expression of CPP. It is concluded that mu-opioid receptors in the rat medial thalamus are involved in the acquisition, but not expression, of morphine-induced CPP.

A simple and rapid high performance liquid chromatography method to determine levofloxacin in human plasma and its use in a bioequivalence study

A simple and rapid HPLC-UV method has been developed for determination of levofloxacin in human plasma. Chromatographic separation was performed on a Kromasil C18 column with the mobile phase consisting of acetonitrile, water, phosphoric acid and triethylamine (14:86:0.6:0.3, v/v/v/v) and flow rate was 1.0 mL/min. The method used ultraviolet detection set at a wavelength of 294 nm. The standard curves were linear over concentration range of 0.05-5.0 μg/mL (r > 0.99). The method was simple, rapid, precise, accurate and suitable for routine bioequivalence study. The method was successfully applied to the bioequivalence study of two different levofloxacin hydrochloride capsules in Chinese healthy volunteers.

Pulsed Rayleigh wave scattered at a surface crack

This paper investigates Rayleigh wave interaction with machined slots on flat aluminium blocks to simulate surface breaking cracks. Using a finite element method, Rayleigh wave scattering by narrow slots of varied depth ranging from 0.5 mm to 20 mm is calculated. Pulsed wideband Rayleigh waves with a centre frequency of 590 kHz and -6 dB bandwidth of 520 kHz is considered. Reflection and transmission coefficients are calculated and compare well with the published literature. We and other workers have reported enhancement of the measured amplitude or particle velocity of an apparent Rayleigh wave close to a surface defect. In this paper, it is found that the predicted enhancement of in-plane components of particle velocities close to a crack is significantly higher than that of the out-of-plane components of particle velocities which appears to be mainly due to the mode-converted surface skimming longitudinal wave from the crack that has mainly in-plane components near the sample surface. The enhancement of the in-plane particle velocity will be observed regardless of the type of in-plane sensitive ultrasonic detector used. The explanation of the discrepancy of the reflection and transmission coefficients obtained by pulsed and narrow band or pseudo continuous Rayleigh waves is discussed. The later-arriving Rayleigh waves from reverberation along the inside of the crack surface are observed, as has been previously reported by other workers, and this may also be used to gauge slot depth.

Enhanced Maturation and Functional Capacity of Dendritic Cells Induced by Mannosylated L2 Domain of ErbB2 Receptor

The nature of antigens and functional state of dendritic cells (DC) are important in antigen presentation. The ability of DC for the induction of T-cell responses is promoted by maturation. It has been confirmed that mannose receptors mediate highly efficient endocytosis and presentation of mannosylated proteins. In the present study, L2 domain of ErbB2 ectodomain was expressed in Escherichia coli, purified and mannosylated. The maturation and functional capacity of DC induced by mannosylated L2 (mL2) protein were investigated. The results showed that L2 protein could induce DC maturation, which was accompanied by elevated expression of MHC and co-stimulatory molecules. The effect of mL2 protein on DC maturation was more remarkable than that of non-mL2 proteins. Uptake of mL2 antigens by DC was more efficient. Furthermore, the T cells can be stimulated to proliferate in vitro and secrete Th1 and Th2 cytokines. Higher levels of both IFN-gamma and IL-10 were detected from the T cells stimulated by mL2-pulsed DC, suggesting a concurrent activation of CD4+ and CD8+ T cells. The results demonstrated that L2 domain of ErbB2 receptor is an immunodominant molecule. The mL2 domain of ErbB2 can induce an enhanced maturation and functional capacity of DC. It may become an effective strategy to induce anti-ErbB2 response.

The negative cell cycle regulator, Tob (transducer of ErbB-2), is a multifunctional protein involved in hippocampus-dependent learning and memory

Tob (transducer of ErbB2) is a negative cell cycle regulator with anti-proliferative activity in the periphery. Using a behavioral screening paradigm to look for novel gene functions in the brain, we identified Tob as a brain-expressed protein involved in learning and memory. Behavioral training of fear-conditioning triggered a transient elevation of Tob protein, which preceded the formation of long-term memory. Functional perturbation of Tob by intra-CA1 infusion of antisense oligonucleotides in rats impaired spatial learning and memory in the Morris water maze and long-term memory for contextual fear conditioning, two behavioral paradigms that require the hippocampus. Furthermore, long-term potentiation was suppressed by Tob antisense infusion into the CA1 region. Together, these results indicate that the negative cell cycle regulator Tob is a multifunctional protein involved in hippocampus-dependent learning and memory.

Structural analysis of the epitopes on erbB2 interacted with inhibitory or non-inhibitory monoclonal antibodies

erbB2 oncogene encodes a growth factor receptor. The overexpression of erbB2 was correlated with more aggressive tumors and a poorer prognosis. Some antibodies directed to this molecule have an antitumor effect in vivo, but some antibodies do not. In an attempt to understand the molecular basis of the anti-erbB2 antibody interaction with erbB2 ectodomain (ECD), we analyzed binding epitopes on erbB2 for inhibitory and non-inhibitory antibodies, Herceptin and HF by computer-guided protein engineering and site-directed mutagenesis. Two different interaction domains were identified by molecular docking, computer graphics and distance geometry method and confirmed through studies on a series of mutants of erbB2 ECD. Non-inhibitory antibody HF only recognized N-terminal portion of erbB2 ECD, but inhibitory antibody Herceptin bound to C-terminal portion of it exclusively. The region interacted with inhibitory antibody Herceptin can be an important target for anticancer therapies.

Combined effects of tamoxifen and a chimeric humanized single chain antibody against the type I IGF receptor on breast tumor growth in vivo

Proliferative and anti-apoptotic actions of IGFs are mediated by the IGF-I receptor (IGF-IR), to which both IGF-I and -II bind with high affinity. We previously reported that alphaIGF-IR scFv-Fc (scFv-Fc) consisting of the alphaIGF-IR scFv and human IgG (1) Fc domain retained general characteristics of the parental 1H7 monoclonal antibody, and significantly suppressed MCF-7 tumor growth. We proposed IGF-IR down-regulation as a possible mechanism for inhibition of MCF-7 tumor growth. To further determine the therapeutic potentials of this approach, in vivo effects of this antibody on breast tumor growth were evaluated in the absence or presence of tamoxifen (Tam) using a T61 human breast tumor model. T61 xenograft growth in athymic mice was compared under five conditions, PBS, scFv-Fc, Tam, scFv-Fc+Tam, and control antibody. While treatment with PBS and control antibody did not affect T61 tumor growth, scFv-Fc, Tam, and scFv-Fc+Tam treatments significantly suppressed the tumor growth during the first two weeks of treatment. Although the growth inhibitory effect of scFv-Fc during the first two weeks was significant, the tumor grew as rapidly as PBS-treated tumors thereafter. This rapid tumor growth was suppressed when scFv-Fc was combined with Tam. Throughout four weeks, the combined Tam+scFv-Fc treatment was more effective in inhibiting the T61 tumor growth than scFv-Fc or Tam treatment alone. scFv-Fc treatment down-regulated IGF-IR which appears to contribute to tumor growth inhibition. This study provides evidence that simultaneous targeting of IGF-IR and the estrogen receptor may enhance the therapeutic effect.

[Successful engraftment of HLA-identical sibling cord blood transplantation in an adult with chronic myelogenous leukemia]

OBJECTIVE

To explore the feasibility of cord blood transplantation (CBT) for the treatment of adult hematological malignancies and its long-term hematopoiesis reconstitution and transplantation-related complications.

METHODS

An 18 years old patient (body weight 75 kg) with chronic myelogenous leukemia in first chronic phase received HLA-identical sibling CBT after conditioning with modified busulfan/cyclophosphamide (Bu/CTX) regimen. The transplanted number of nucleated cells was 1.73 x 10(7)/kg of body weight, and that of CD34+ cells 2. 7 x 10(5)/kg. Cyclosporin A and methylprednisolone were given as prophylaxis against graft versus-host disease (GVHD).

RESULTS

The neutrophil count rose to above 0.5 x 10(9)/L on day 18 and platelet count exceeded 50 x 10(9)/L on day 36. Gene analysis showed that bone marrow cells had completely changed to donor's type on day 80. The patient was diagnosed with grade IV acute hepatic GVHD complicated with CMV infection because of severe jaundice on day 90. After the administration of additional immunosuppressive agents, antiviral agents, plasma exchange and in vitro billirubin adsorption, the complications were well controlled. In the follow-up of 24 months', the patient's general condition is good without obvious hepatic dysfunction and Ph chromosome and bcr/abl fusion gene of bone marrow cells were persistently negative.

CONCLUSION

It is the first case reported in China that adult patient with leukemia has been successfully treated by allogeneic CBT, and this indicates that CBT is feasible in the treatment of adult patient with leukemia.

[Allogeneic peripheral blood stem cell transplantation for high-risk leukemia]

OBJECTIVE

To study the effects of allogeneic peripheral blood stem cell transplantation (allo-PBSCT) in high-risk leukemia.

METHODS

From October 1995 to December 2000, 25 patients with high-risk leukemia (median age 34 years, range 5.5-52 years) were transplanted with peripheral blood stem cells from their HLA-identical sibling donors. Among them, 15 patients suffered from acute leukemia (ALL) (one ph+ ALL in CR1, seven in CR2 or greater, and seven in relapse, including two in relapse after the first all-BMT), four patients suffered from chronic myelocytic leukemia (CML) (in CP2, AP, BC, and relapse after BMT respecively), 6 patients suffered from myelodys plastic syndrome (MDS), including one case of refractory anemia with excess of blasts (REAB), one case of refractory anemia with excess of blasts in trransformation (REAB-T), and 4 cases of acute leukemia secondary to MDS. The graft versus host disease (GVHD) prophylaxis included administration of cyclosporine and methotrexate.

RESULTS

All patients were successfully engrafted. The median times (range) for their neutrophil returning to > or = 0.5 x 10(9)/L and for platelet returning to > or = 20 x 10(9)/L were 14 (10-18) days and 11 (7-45) days after transplantation resprctively. Grade II acute GVHD occurred in 12 patients with an incidence rate of 48%. Grade III GVHD was found in one patient (4%). No grade IV GVHD was seen. Among the 23 evaluable patients, 16 were diagnosed as chronic GVHD (70%). The actual transplant-related mortality was 16%. Leukemia relapse occurred in 6 patients, four of them received donor lymphocyte infusion (DLI) and achieved remission again. Nineteen patients were alive and disease-free with a median follow-up time of 304 (94-1,963) days. The two-year probability of overall survival, disease-free survival (DFS), and relapse rates were 64%, 58%, and 25% respectively.

CONCLUSION

Allo-PBSCT decreases the relapse rate, increases the disease-free survival rate for patients with high-risk leukemia. All-PBSCT may be a better choice for patients with high-risk hematological maligmancies.

[Effect of interferon-alpha on the prognosis of bone marrow transplantation in chronic myeloid leukemia]

OBJECTIVE

To investigate whether prior interferon alfa (IFN-alpha) treatment affects the outcome of allogeneic bone marrow transplantation.

METHODS

The outcome of 85 patients with chronic myelogenous leukemia (CML) in first chronic phase received transplants from an HLA-identical sibling donor was analyzed. Of the 85 patients, 30 did not receive IFN-alpha, whereas 30, 15 and 10 patients received IFN-alpha 3 x 10(6) units 3-4 times per week for < 6, 6-12 and > 12 months before transplant combined with hydroxyurea and/or HA regimen (H: Harringtonine; A: Ara-C) respectively.

RESULTS

Pretransplant IFN-alpha therapy for > or = 6 months was associated with an increased risk of severe (grade III-IV) acute graft-versus-host disease (GVHD) (P < 0.01) as compared to that in < 6 months or no IFN-alpha therapy. No influence of pretransplant IFN-alpha treatment on engraft, cGVHD, VOD, relapse and TRM (transplant-related mortality) was found. Survival rate of IFN-alpha therapy < 6 months group (90.0%) was higher than that of no IFN-alpha group (68.9%) or > 12 months group(60.0%) (P < 0.05).

CONCLUSION

It was found that there was a trend towards an improved survival in the IFN-alpha < 6 months group. Pretransplant IFN-alpha therapy for > or = 6 months was associated with an increased risk of severe aGVHD.

[Cytomegalovirus enteritis in recipients of allogeneic peripheral blood stem cell transplantation]

OBJECTIVE

To report 6 cases of cytomeganlovirus (CMV) enteritis in allogeneic bone marrow transplantation (allo-BMT) or peripheral blood stem cell transplantation(PBSCT) recipients and the outcome after treatment.

METHODS

The 6 patients suffered from leukemia and received allo-BMT or allo-PBSCT.

RESULTS

Five of the 6 patients had acute GVHD II-III at 42, 26, 66, 45 and 57 days after transplantation respectively and they recovered after proper treatment. However they soon had severe diarrhea, abdominal pain or/and gastrointestinal bleeding, 5 of the 6 patients received endoscopic examination with biopsy at 50, 57, 80, 65, 35 days after transplantation respectively. They were all diagnosed as having CMV enteritis based on the presence of cytomegalic cells on mucosal biopsy specimens stained with hematoxylin and eosin. Meanwhile the immunoperoxidase stain of histologic specimens for CMV antigen or in situ hybridization by CMV DNA probe was positive. One patient was diagnosed CMV enteritis at 138 days after transplantation based on the clinic and response to therapy. They received antiviral treatment with ganciclovir (DHPG) 500 mg/d for 4 to 21 days, foscarnet 2.4 g q8 h or 4.8 g q12 h for 21 to 90 days, garlic extract 60-120 mg/d, globulin and other supportive measures. All the 6 cases had complete clinical response.

CONCLUSION

CMV enteritis should be diagnosed as soon as possible with histopathologic examination and early proper treatment may lead to good clinical response.

[An exploration of animal behavior screen platform for novel gene function in central nervous system]

For the purpose of large-scale screening of novel gene functions in mammalian nervous system, we have developed an animal behavior-monitoring platform employing antisense-oligo technology. Twenty genes of different categories were chosen from a low abundant gene (c)DNA sub-library of rat brain. Antisense oligo-nucleotides of these genes were designed and synthesized according to the homologues of the genes in mouse for mouse behavior tests. These antisense oligos were injected into the lateral ventricles of mouse brain using a Hamilton micro-syringe, with saline and oligos of scramble sequences as controls. These mice were tested with the following behavior model paradigms: metabolism, open field behavior, tail flick latency, and step-down test. Out of the 20 genes tested, 14 genes showed significant behavioral differences from the control groups at the level of P value less than 0.05 or 0.001 in different behavior animal models.

The human gC1qR/p32 gene, C1qBP. Genomic organization and promoter analysis

gC1qR is an ubiquitously expressed cell protein that interacts with the globular heads of C1q (gC1q) and many other ligands. In this study, the 7.8-kilobase pair (kb) human gC1qR/p32 (C1qBP) gene was cloned and found to consist of 6 exons and 5 introns. Analysis of a 1.3-kb DNA fragment at the 5'-flanking region of this gene revealed the presence of multiple TATA, CCAAT, and Sp1 binding sites. Luciferase reporter assays performed in different human cell lines demonstrated that the reporter gene was ubiquitously driven by this 1.3-kb fragment. Subsequent 5' and 3' deletion of this fragment confined promoter elements to within 400 base pairs (bp) upstream of the translational start site. Because the removal of the 8-bp consensus TATATATA at -399 to -406 and CCAAT at -410 to -414 did not significantly affect the transcription efficiency of the promoter, GC-rich sequences between this TATA box and the translation start site may be very important for the promoter activity of the C1qBP gene. One of seven GC-rich sequences in this region binds specifically to PANC-1 nuclear extracts, and the transcription factor Sp1 was shown to bind to this GC-rich sequence by the supershift assay. Primer extension analysis mapped three major transcription start regions. The farthest transcription start site is 49 bp upstream of the ATG translation initiation codon and is in close proximity of the specific SP1 binding site.

Desiccation tolerance in human cells

The ability to desiccate mammalian cells while maintaining a high degree of viability would have implications for many areas of biological science, including tissue engineering. Previously, we reported that introduction of the genes for trehalose biosynthesis allowed human cells in culture to be reversibly desiccated for up to 5 days. Here, we have further investigated the factors that allow human cells to survive in the desiccated state. The most important finding is that vacuum greatly enhances the ability of human cells in culture to withstand desiccation. In fact, cells dried slowly and stored under vacuum are able to withstand desiccation even in the absence of added carbohydrates or polyols. In addition to vacuum, the rate of desiccation, the temperature at which cells are maintained, the degree of confluence when dried, and the presence or absence of light have a large effect on the ability to retain viability in the desiccated state. Our data are consistent with a model in which cells can retain viability if they are desiccated in such a way that cellular structures are maintained. However, gradual loss of viability may be due to damage that occurs over time in the desiccated state, perhaps due to free radicals. Further optimization of the process for desiccating and maintaining cells is required before long-term storage of desiccated cells can be achieved.

[Detection of TTV DNA and TTV IgG in 328 serum samples]

OBJECTIVE

To investigate the prevalence of TT virus(TTV) in a variety of populations in China.

METHODS

TTV DNA and anti TTV IgG were simultaneously tested by PCR and ELISA.

RESULTS

The positive rate of TTV DNA in the samples of 81 normal subjects, 92 blood donors, 123 hepatitis A-G patients and 32 hepatitis non A-G patients were 2.5%, 2.2%, 19.5% and 28.1%, respectively; and anti-TTV IgG was 1.2%, 3.7%, 26.8% and 34.4%, respectively. There were significant differences between the normal and the blood donor group and the hepatitis group; and among multi-infectious cases, the infection rate of TTV with HBV was as high as 75.0%.

CONCLUSION

The investigation indicated that TTV infection was very popular in different groups. Some of the normal and blood donor groups infected with TTV could become healthy carries of virus. And the hepatitis patients were the high risk group. In addition, TTV may be transmitted via other pathways besides blood.

Epidemiological study of pathogenic fungi in China: 1986 and 1996

OBJECTIVE

An annual decade epidemiological survey of pathogenic fungi of inpatients or outpatients includes more than 25 provinces in China has been done in 1986 and 1996.

METHODS

In 1986, there were a total of 9096 strains of pathogenic fungi collected from more than 41 units of 25 provinces in China. 10 years late, 18,085 strains of pathogenic fungi from 41 units of 25 provinces were collected from January 1st to December 31st in 1996.

RESULTS

The results showed that during this decade the prominent pathogenic fungus was Trichophyton rubrum, but its ratio gradually decreased. On the contrary, Candida albicans gradually increased in its ratio from 5th in 1986 to 2nd in 1996.

CONCLUSION

The pathogenic fungi in China have changed greatly in the past decade from 1986 to 1996.

The sequence of the human genome

A 2.91-billion base pair (bp) consensus sequence of the euchromatic portion of the human genome was generated by the whole-genome shotgun sequencing method. The 14.8-billion bp DNA sequence was generated over 9 months from 27,271,853 high-quality sequence reads (5.11-fold coverage of the genome) from both ends of plasmid clones made from the DNA of five individuals. Two assembly strategies-a whole-genome assembly and a regional chromosome assembly-were used, each combining sequence data from Celera and the publicly funded genome effort. The public data were shredded into 550-bp segments to create a 2.9-fold coverage of those genome regions that had been sequenced, without including biases inherent in the cloning and assembly procedure used by the publicly funded group. This brought the effective coverage in the assemblies to eightfold, reducing the number and size of gaps in the final assembly over what would be obtained with 5.11-fold coverage. The two assembly strategies yielded very similar results that largely agree with independent mapping data. The assemblies effectively cover the euchromatic regions of the human chromosomes. More than 90% of the genome is in scaffold assemblies of 100,000 bp or more, and 25% of the genome is in scaffolds of 10 million bp or larger. Analysis of the genome sequence revealed 26,588 protein-encoding transcripts for which there was strong corroborating evidence and an additional approximately 12,000 computationally derived genes with mouse matches or other weak supporting evidence. Although gene-dense clusters are obvious, almost half the genes are dispersed in low G+C sequence separated by large tracts of apparently noncoding sequence. Only 1.1% of the genome is spanned by exons, whereas 24% is in introns, with 75% of the genome being intergenic DNA. Duplications of segmental blocks, ranging in size up to chromosomal lengths, are abundant throughout the genome and reveal a complex evolutionary history. Comparative genomic analysis indicates vertebrate expansions of genes associated with neuronal function, with tissue-specific developmental regulation, and with the hemostasis and immune systems. DNA sequence comparisons between the consensus sequence and publicly funded genome data provided locations of 2.1 million single-nucleotide polymorphisms (SNPs). A random pair of human haploid genomes differed at a rate of 1 bp per 1250 on average, but there was marked heterogeneity in the level of polymorphism across the genome. Less than 1% of all SNPs resulted in variation in proteins, but the task of determining which SNPs have functional consequences remains an open challenge.

[Relationship between soluble Fas ligand levels and complications after allogeneic bone marrow transplantation]

OBJECTIVE

To evaluate the implications of soluble Fas ligand (sFasL) in acute graft-versus-host disease (aGVHD) and discriminating symptoms of aGVHD from those of infection.

METHODS

Plasma levels of sFasL were assessed in 84 plasma samples from 13 patients after allogeneic BMT using a sandwich enzyme-linked immunological assay (ELISA). Plasma sFasL levels of the patients before BMT and at different time points in the post-BMT period were measured. The results were analysed for correlation with aGVHD and infections.

RESULTS

Plasma sFasL levels were significantly higher in patients with grade II - IV aGVHD than that in those with grade 0 - I aGVHD (P = 0.02). There was no statistic difference in plasma sFasL levels between the infectious and non-infectious patients. In the seven grade II - IV aGVHD patients, the plasma sFasL levels pre-BMT were much lower than that in the six grade 0 - I aGVHD patients.

CONCLUSIONS

sFasL may be useful for the diagnosis of aGVHD and for differentiating aGVHD from other BMT related complications. The high level of plasma sFasL pre-BMT may be of importance in decreasing the occurrence of aGVHD after BMT.

An intronic downstream enhancer promotes 3' splice site usage of a neural cell-specific exon

The human nonmuscle myosin heavy chain B gene contains a 30-nucleotide alternative exon, N30, that is included in the mRNA from neural cells but is skipped in all other cells. We have previously identified an intronic distal downstream enhancer (IDDE) region that is required for neural cell-specific inclusion of N30. In this study, we investigated the mechanism by which the IDDE promotes N30 exon usage. In vitro splicing analysis using neural cell nuclear extracts and two-exon pre-mRNA substrates, which consist of the N30 exon and either the upstream (E5) or downstream (E6) exon, demonstrates that the IDDE activates upstream E5-N30 splicing by facilitating early prespliceosome complex formation. The IDDE has no effect on N30-E6 splicing where the IDDE resides. Inspection of splice site consensus sequences shows that a polypyrimidine (Py) tract preceding N30 is suboptimal for U2AF binding. Optimizing the Py tract completely relieves the requirement for the IDDE in E5-N30 splicing in vitro. In transfected cells, the wild-type minigene transcripts, which consist of three exons, E5, N30, and E6, undergo neural cell-specific and IDDE-dependent alternative splicing of N30. Optimizing the Py tract in minigenes also completely relieves the requirement for the IDDE in N30 inclusion. Furthermore, overexpression of the truncated U2AF65, which contains the arginine and serine dipeptide-rich domain and linker domain, but lacks the RNA binding domain, selectively inhibits the IDDE-mediated N30 inclusion in mRNA from the wild-type minigene in a dominant negative fashion. These results support the hypothesis that the IDDE facilitates the recognition of the 3' splice site preceding N30 by a network of protein-protein interactions implicated in the recruitment of U2AF to a suboptimal Py tract.