Cytological examination of rat amniotic epithelial cells and cell transplantation to the liver

It is hoped that amniotic epithelial cells can be useful in cell-mediated gene therapy. We report here an experimental cell transplantation model of amniotic cells in rats. There is an anatomical difference between human and rodent embryos. We established a method to isolate amniotic cells that are equivalent to human amniotic epithelial cells. An amniotic membrane distinct from the yolk sac was carefully collected and teased in saline containing deoxyribonuclease and hyaluronidase, followed by collagenase digestion. The cell yield was approximately 10(6) cells per pregnant female (10(5) cells per fetus), roughly in proportion to the age of fetus used, and 60% of the isolated cells were attached to the dish under culture conditions. Telomerase activity was higher in the cells isolated from fetuses in the middle stage (day 13.5 to 15.5) than in the late stage (day 17.5 to 21.5). Adherent cells exhibited two to three times more cell division, resulting in a ninefold increase in the number of cells. Immunohistochemical analysis revealed that approximately half of the adherent cells were albumin positive and formed clusters. The senescent cells survived for 2 months without apparent morphological changes. The adherent cells were able to be stored in liquid nitrogen and had a viability of 70% when thawed. Gene transduction with adenovirus vector was highly effective for rat amniotic cells. Transplantation of lacZ transfected amniotic cells into syngeneic rat liver resulted in the integration of the transplanted cells in the liver structure and the cells survived for at least 30 days.

Drosophila mitochondrial transcription factor A: characterization of its cDNA and expression pattern during development

We cloned a cDNA for Drosophila mitochondrial transcription factor A (D-mtTFA) and characterized the recombinant protein. In Drosophila Kc cells, D-mtTFA was localized in the mitochondria, but not in the nucleus. By repetitive precipitation with His-tag and PCR amplification, the consensus nucleotide sequence for D-mtTFA-binding was determined to be 5'-TTATC/G. The binding sequence was found to be clustered in the A + T region of mitochondrial DNA which is suggested to be a replication origin and promoter region for light strand and heavy strand. We found a DNA replication-related element (DRE)-like sequence located upstream of the transcription initiation site of the D-mtTFA gene and obtained results indicating that DRE-binding factor (DREF) can bind to the DRE-like sequence of the D-mtTFA gene. The data suggest that transcription of the D-mtTFA gene is under control of the DRE/DREF regulatory system. Based on these results, the functions of D-mtTFA were discussed in relation to mitochondrial biogenesis of Drosophila melanogaster.

Terminal deoxynucleotidyltransferase is negatively regulated by direct interaction with proliferating cell nuclear antigen

BACKGROUND

The repertoires of Ig and TcR are generated by a combinatorial rearrangement of variable (V), diversity (D), and joining (J) segments (V(D)J recombination) in B- and T-cells. Terminal deoxynucleotidyltransferase (TdT) adds extra nucleotides (N nucleotides) at the junctions of the gene segments to enhance the Ig and TcR genes diversity. Using an anti-TdT antibody column, TdT has been purified as a member of a megadalton protein complex from rat thymus. The N region would be synthesized with the large protein complex.

RESULTS

The cDNAs for proliferating cell nuclear antigen (PCNA) were isolated by yeast two-hybrid screening as the gene products which directly interacted with TdT. The interaction between PCNA and TdT was confirmed by co-immunoprecipitation, both in vitro and in vivo. TdT binds directly to a PCNA trimer, as shown by gel filtration. TdT interacts with PCNA in its DNA polymerization domain (DPD), but not in its BRCA-1 C-terminal (BRCT) domain. TdT activity was reduced to 17% of the maximum value by TdT/PCNA complex formation.

CONCLUSION

TdT interacts directly with PCNA through its DPD. A functional consequence of this interaction is the negative regulation of TdT activity. These findings suggest that TdT catalyses the addition of N nucleotides under the negative control of PCNA during V(D)J recombination.

Terminal deoxynucleotidyltransferase directly interacts with a novel nuclear protein that is homologous to p65

BACKGROUND

Terminal deoxynucleotidyltransferase (TdT) is a DNA polymerase that enhances Ig and TcR gene diversity in the N region in B- and T-cells. TdT is found as a member of a large protein complex in the lysate of the thymocytes. To elucidate the molecular mechanism of the synthesis of the N region, we first attempted to isolate the genes with products that are interacting directly with TdT.

RESULTS

Using a yeast two-hybrid system, we isolated a cDNA clone encoding a novel nuclear protein that interacts with TdT. This protein was designated as TdT interacting factor 1 (TdIF1). TdIF1 has a high degree of homology to the transcription factor p65, which belongs to the nuclear receptor superfamily. TdIF1 contains HMG-I and HMG-Y DNA binding domains (AT-hooks) and can bind to single- and double-stranded DNA. TdT and TdIF1 were co-eluted at position 232 kDa by gel filtration of MOLT4 lysate. TdIF1 can enhance TdT activity fourfold in vitro assay system using oligo(dT)16 as primers.

CONCLUSIONS

TdIF1 binds directly to TdT, both in vitro and in vivo. TdIF1 and TdT exist as the members of a 232 kDa protein complex. TdIF1 can enhance TdT activity maximum fourfold in vitro assay system, suggesting that it positively regulates the synthesis of the N region during V(D)J recombination in the Ig and TcR genes.

Novel role of phosphatidylinositol 3-kinase in CD28-mediated costimulation

Ligation of the CD28 surface receptor provides a major costimulatory signal for full scale T cell activation. Despite extensive studies, the intracellular signaling pathways delivered by CD28 ligation are not fully understood. A particularly controversial matter is the role of phosphatidylinositol 3-kinase (PI3K) in CD28-mediated costimulation. It is known that the binding site for PI3K and Grb-2 lies nested within the YMNM motif of the CD28 cytoplasmic domain. To elucidate the role of PI3K during CD28-mediated interleukin-2 (IL-2) production, CD28 YMNM point and deletion mutants were expressed in Jurkat cells. We then measured IL-2 promoter activation after CD28 ligation. Our results showed that the Y189F mutant, which disrupts binding by PI3K, and the YMNM deletion mutant both demonstrated reduced but significant activity for IL-2 promoter activation. In contrast, the N191A mutant, which retains PI3K binding ability, resulted in a complete abrogation of activity, suggesting that PI3K mediates a negative effect upon transcriptional activation of the IL-2 gene. Consistent with this idea, we found that the addition of a PI3K pharmacological inhibitor augmented IL-2 promoter activity, whereas coexpression of a constitutively active form of PI3K reduced this activity. Taken together, these data indicate that PI3K, when associated with the YMNM motif, may act as a negative mediator in CD28-mediated IL-2 gene transcription.

Molecular cloning and expression during development of the Drosophila gene for the catalytic subunit of DNA polymerase epsilon

We have cloned the genomic DNA and cDNA of Drosophila DNA polymerase epsilon (pol-epsilon) catalytic subunit (GenBank No. AB035512). The gene is separated into four exons by three short introns, and the open reading frame consists of 6660 base pairs (bp) capable of encoding a polypeptide of 2220 amino acid residues. The calculated molecular mass is 255018, similar to that of mammalian and yeast homologues. The deduced amino acid sequence of the pol-epsilon catalytic subunit shares approximately 41% identity with human and mouse homologues as well as significant homology those of C. elegans, S. cerevisiae and S. pombe. Similar to the pol-epsilon catalytic subunits from other species, the pol-epsilon catalytic subunit contains domains for DNA polymerization and 3'-5' exonuclease in the N-terminal region, and two potential zinc-finger domains in the C-terminal regions. Interestingly, a 38 amino acid sequence in the C-terminal region from amino acid positions 1823 to 1861 is similar to the site for Mycoplasma ATP binding and/or ATPase domain (GenBank No. P47365). Northern hybridization analysis indicated that the gene is expressed at the highest levels in unfertilized eggs, followed by zero to 4h embryos and adult females, and then embryos at other embryonic stages, instar larva stages and adult males. Low levels of the mRNA were also detected at the pupa stage. This pattern of expression is similar to those of DNA replication-related enzymes such as DNA polymerase alpha and delta except for the high level of expression in adult males.

The UL34 gene product of herpes simplex virus type 2 is a tail-anchored type II membrane protein that is significant for virus envelopment

The UL34 gene of herpes simplex virus type 2 (HSV-2) is highly conserved in the herpesvirus family. The UL34 gene product was identified In lysates of HSV-2-infected cells as protein species with molecular masses of 31 and 32.5 kDa, the latter being a phosphorylated product. Synthesis of these proteins occurred at late times post-infection and was highly dependent on viral DNA synthesis. Immunofluorescence assays revealed that the UL34 protein was localized in the cytoplasm in a continuous net-like structure, closely resembling the staining pattern of the endoplasmic reticulum (ER), in both HSV-2-infected cells and in cells transiently expressing UL34 protein. Deletion mutant analysis showed that this colocalization required the C terminus of the UL34 protein. The UL34 protein associated with virions but not with A, B or C capsids. We treated virions, HSV-2-infected cells and cells expressing the UL34 protein with a protease in order to examine the topology of the UL34 protein. In addition, we constructed UL34 deletion mutant proteins and examined their intracellular localization. Our data strongly support the hypothesis that the UL34 protein is inserted into the viral envelope as a tail-anchored type II membrane protein and is significant for virus envelopment.

Strong, long-term transgene expression in rat liver using chicken beta-actin promoter associated with cytomegalovirus immediate-early enhancer (CAG promoter)

For successful gene therapy in hepatic enzyme deficiencies, it is essential to use promoters that can maintain strong transcriptional activity for the long term in the liver. Using Gunn rats, a model animal for Crigler-Najjar syndrome type I, the long-term transcriptional function of the CAG promoter (a combination of chicken beta-actin promoter and cytomegalovirus immediate-early enhancer) was evaluated in the rat liver. We constructed a plasmid pCAGGHUGT, containing expression cassettes of human bilirubin UDP-glucuronosyltransferase (BUGT) and hygromycin phosphotransferase, under the control of the CAG promoter and murine phosphoglycerate kinase promoter, respectively. Conditionally immortalized Gunn rat hepatocytes (IGRH), which had been established using mutant SV40 large T antigen ((TS)T), were transfected with pCAG-GHUGT. A stably transfected clone IGRHUGT, expressing a high level of BUGT, was obtained after selection with hygromycin. At 33 degrees C, the cells doubled in number in approximately 72 h; however, at 37 degrees C, cell proliferation stopped, indicating that the characteristic of temperature-dependent proliferation was retained in this clone. Ten million cells were injected into the spleen of syngeneic Gunn rats five times at 10-day intervals. Serum bilirubin levels were reduced by 45-50% at 70 days after the first transplantation and remained so throughout the duration of the study (120 days). These results suggested that the CAG promoter was able to maintain strong transcriptional activity in rat liver for at least 120 days.

Isolation, purification, and characterization of a collagen-associated serpin, caspin, produced by murine colon adenocarcinoma cells

A 45-kDa serpin secreted by a murine colon adenocarcinoma cell line, colon26, was isolated, purified, and characterized. It was found to bind specifically to type I collagen with high affinity and to type III collagen with lower affinity. Immunohistochemical studies of murine embryonic tissues showed a specific distribution of this collagen-associated serpin, named caspin, in relation to the formation of bone, cartilage, teeth, and basement membrane. The expression of caspin in high and low lung metastatic subclones of colon26 cell lines was inversely correlated with their metastatic capacity: low lung metastatic cells secreted higher amounts of caspin than their high lung metastatic counterparts. Caspin also demonstrated high homology with human pigment epithelium-derived factor/early population doubling level cDNA-1, which reportedly induces neuronal differentiation of human retinoblastoma cells and is expressed in association with G0 growth arrest. These findings suggest that caspin/pigment epithelium-derived factor/early population doubling level cDNA-1 is a novel factor that might play a crucial role in embryogenesis and tumor metastasis through binding to the extracellular matrix.

Structure and organization of the gene encoding human selenoprotein

We have isolated a genomic clone encoding human selenoprotein P including the putative promoter region. The gene spans 12 kb and consists of five exons with a start codon in the second exon. A typical TATA sequence, the recognition motifs for a GATA-binding factor and the liver-specific factors, HNF-1 and HNF-3, were detected upstream from the transcription start point.

Coexpression of cell-surface immunoglobulin (sIg), terminal deoxynucleotidyl transferase (TdT) and recombination activating gene 1 (RAG-1): two cases and derived cell lines

While it is generally agreed that in the lymphoid differentiation of B lineage cells there is no stage in which cell-surface immunoglobulin (sIg) and terminal deoxynucleotidyl transferase (TdT) are expressed simultaneously, a few B cell acute lymphoblastic leukemia (B-ALL) cases with this phenotype have been reported. Two such cases and the derived cell lines are reported here, in which the expression of recombination activating gene-1 (RAG-1) was also detected. One case was a CD19+ CD22+ HLA-DR+ sIg+ (gamma, kappa) B-ALL. The cell line (Bay9I) also expressed CD10. Karyotypic analysis revealed t(14;18)(q32;q21) and additional aberrations. In the other case, the fresh leukemia cells expressed CD19, CD24 and HLA-DR antigen. The derived cell line (Tree92) also expressed CD22 and sIg (mu, lambda). The karyotype of the Tree92 cells was t(8;14)(q24;q32) with additional aberrations. Tree92 is the first established cell line having both t(8;14)(q24;q32) and TdT. TdT was detected by Northern blotting as well as indirect immunofluorescence analysis. In addition, both Bay9I and Tree92 expressed RAG-1, as detected by Northern blot analysis. Cross-linking of sIg on Tree92 cells with anti-mu antibody led to significant down-regulation of RAG-1 expression. It seems that there is a sIg+ TdT+ RAG-1+ B lineage differentiation stage, and that signaling through sIg can modulate RAG-1 expression.

Crigler-Najjar syndrome type II is inherited both as a dominant and as a recessive trait

Crigler-Najjar syndrome type II (CN-II) is caused by a severely reduced hepatic activity of bilirubin UDP-glucuronosyltransferase (UGT). Recently, by the analysis of the genetic background of CN-II patients, it has been clarified that the patients carry homozygous missense mutations or nonsense plus missense mutations on the gene for UGT, and CN-II was inherited as an autosomal recessive trait. We encountered a new case which had a nonsense mutation caused by a single nucleotide substitution on one allele. This indicates that CN-II is also inherited as a dominant trait as well as a recessive trait. Expression study in vitro strongly suggests that the disease in this case is caused by a dominant negative mutation by forming a heterologous subunit structure.

Gilbert's syndrome is caused by a heterozygous missense mutation in the gene for bilirubin UDP-glucuronosyltransferase

Gilbert's syndrome, which is characterized by chronic, non-hemolytic unconjugated hyperbilirubinemia, is caused by a reduction in the activity of hepatic bilirubin UDP-glucuronosyltransferase (UGT). Here, we report that all examined patients with this disease carried missense mutations in the gene for UGT and that the mutations were heterozygous. An expression study in COS cells in vitro, using the expression vector pcDL that carried the mutated gene for UGT from a patient, indicated that approximately 14% of the normal UGT activity was expressed. However, the UGT activity of the patient with Gilbert's syndrome was unexpectedly < 50% of the normal, perhaps as the result of the dominant negative nature of the mutation.

Analysis of genes for bilirubin UDP-glucuronosyltransferase in Gilbert's syndrome

Gilbert's and Crigler-Najjar syndromes are characterised by unconjugated hyperbilirubinaemia due to complete and partial absence of bilirubin UDP-glucuronosyltransferase (UGT). Nucleotide sequences of the genes for bilirubin UGT were analysed in six patients with Gilbert's syndrome. All patients had a missense mutation caused by a single nucleotide substitution and the mutations were heterozygous. In addition, relatives of patients with Crigler-Najjar syndrome types I and II, and of those with Gilbert's syndrome were analysed. All ten relatives with mild hyperbilirubinaemia were heterozygotes with respect to each defective allele. These results suggest that Gilbert's syndrome is inherited as a dominant trait.

Isolation of cDNAs for mouse phenol and bilirubin UDP-glucuronosyltransferases and mapping of the mouse gene for phenol UDP-glucuronosyltransferase (Ugtla1) to chromosome 1 by restriction fragment length variations

The mouse gene for phenol UDP-glucuronosyltransferase (UDPGT; Ugtla1) was mapped at 42 cM on chromosome 1, a position identical to that of the gene for bilirubin UDPGT (Ugtla1), from linkage analysis of a three-point cross test with Idh-1, En-1, and Ugtla1 as marker genes. The cDNAs for mouse phenol and bilirubin UDPGTs, isolated after amplification by PCR, shared an identical 3'-half region. Our results strongly suggest that mouse bilirubin and phenol UDPGTs are expressed from a single gene and involve alternative splicing events. We also detected duplication of the gene for phenol UDPGT in all mouse strains examined with the exception of MOL-MIT and SUB-SHH.

Novel leukemic lymphoma with probable derivation from immature stage of natural killer (NK) lineage in an aged patient

A 66-year-old male patient was admitted with dyspnea; physical examination revealed petechiae and systemic lymphadenopathy. Laboratory findings showed leukemia. The blasts in the peripheral blood were negative for cytochemical myeloperoxidase, and had condensed nuclear chromatin with a nucleolus. The histological diagnosis of the biopsied neck lymph node was lymphoblastic lymphoma. The leukemia cells expressed CD2, CD6, CD7, CD13low, CD56, beta chain of IL-2 receptorlow (IL-2R beta), and HLA-DR antigens, but not other pan-T (CD5, CD3, CD4, and CD8); pan-B (CD10, CD19, CD20, and CD24); natural killer (NK) (CD16, CD57); or myeloid (CD33) antigens. Electronmicroscopy revealed convoluted nuclei with conspicuous nucleoli and peripherally condensed heterochromatin. Membrane-bound granules containing an electron dense matrix were observed in the cytoplasm, indicating the NK cell nature of the neoplastic cells. While terminal deoxynucleotidyl transferase (TdT) and cytoplasmic CD3 were not detected by immunofluorescence on fixed smears, Northern blot analysis revealed the gene expression of CD3 epsilon, CD3 zeta, and TdT. Gene rearrangement analysis revealed that the beta, gamma, and delta chains of T-cell receptor (TCR) and immunoglobulin heavy chain (IgH) were of germline genotype. While the overall interpretation of the phenotype and genotype was difficult, the derivation of an immature stage of NK lineage was strongly suggested, based predominantly on the electronmicroscopic features. Despite initially successful chemotherapy, the patient died 14 months after initial presentation.

Mapping of rat bilirubin UDP-glucuronosyl-transferase gene (Ugt1a1) to chromosome region 9q35-->q36

Bilirubin and phenol UDP-glucuronosyltransferases (UGTs) are located on the same chromosome and comprise the UGT1 gene complex. A 1,763-bp cDNA probe (UGT1*0) specific for rat liver bilirubin UGT was used to localize the UGT1 complex locus (Ugt1a1) to chromosome region 9q35-->q36 by fluorescence in situ hybridization. This assignment is the first report on the location of a gene of the rat UGT1 complex using high-resolution banded metaphase chromosomes.

A new type of defect in the gene for bilirubin uridine 5'-diphosphate-glucuronosyltransferase in a patient with Crigler-Najjar syndrome type I

Crigler-Najjar syndrome (CN) type I, which is characterized by the complete absence of bilirubin uridine 5'-diphosphate-glucuronosyltransferase (UGT) activity, is inherited as an autosomal recessive trait associated with unconjugated hyperbilirubinemia. Phenobarbital has no effect on the bilirubin concentration in the serum of patients with CN type I. Recently, cDNA for two human liver bilirubin UGT (UGT1A and UGT1D) were isolated, and their genetic organization was determined. The UGT1A (UGT1*1) and UGT1D (UGT1*4) genes each have a unique exon 1, whereas exons 2-5 are common to both genes. It has been predicted that some defect in the exons common to both genes is responsible for the absence of UGT1A and UGT1D activities in CN type I, and five cases with such a mutation have been reported. We describe here a new type of defect in the gene for bilirubin UGT in a patient with CN type I, namely, an abnormality in the exon 1 that is characteristic of the UGT1A gene. This mutation is a single nucleotide substitution, that is, C is changed to A at base position 840 in UGT1A cDNA, and this change results in a stop codon. Our patient is homozygous for the defect, and his nonconsanguineous parents and elder brother, who are clinically normal, are heterozygous for the defective allele. No mutation was detected in any exons of the UGT1D gene. Our results suggest that a homozygous nonsense or deletion mutation is detected not only in the exons common to UGT1A and UGT1D genes but also in unique exon 1 of UGT1A in CN type I.

Gelatinases and metalloproteinase inhibitor secreted by murine colonic carcinoma cells with differing metastatic potential

Gelatinase activity and inhibitory activity against collagenase were measured in serum-free medium conditioned by murine colonic carcinoma cells with different spontaneous metastatic potentials to the lung. The medium conditioned with poorly metastatic NM11 cells gave higher inhibitory activity than that conditioned with highly metastatic LuM1 cells, while the level of secreted gelatinases in the same medium was lower in NM11 medium than in LuM1 case. Northern analysis showed the higher gene expression of both tissue inhibitor of metalloproteinases (TIMP)-1 and TIMP-2 in NM11 cells than in LuM1 cells, suggesting that both TIMPs are responsible for the increase of inhibitory activity in NM11 conditioned medium. Examination of the balance of gelatinases and inhibitor revealed that the amount of inhibitor exceeded that of gelatinases in the medium conditioned with NM11 cells. In contrast, the medium conditioned with LuM1 cells contained excess amounts of gelatinases. The results indicated a close correlation between the balance of gelatinases and inhibitors and the metastatic behavior of murine tumor cells.

Identification of defect in the genes for bilirubin UDP-glucuronosyl-transferase in a patient with Crigler-Najjar syndrome type II

Crigler-Najjar syndrome (CN) type II is characterized by severe chronic nonhemolytic unconjugated hyperbilirubinemia due to reduced hepatic bilirubin UDP-glucuronosyl-transferase (UGT) activity. Two bilirubin UGT isozymes, UGT1A and UGT1D, have been identified. We analyzed the DNA sequence of the bilirubin UGT genes in a 5-year-old Japanese male patient with CN type II, who had consanguineous parents. Point mutations were found on exons 1 of the UGT1A and UGT1D genes. The abnormalities were single nucleotide substitutions of G by A and of T by C at base position 211 of UGT1A cDNA and at base position 395 of the UGT1D, respectively. We found another single nucleotide substitution of T by G on exon 5 common to both genes at base position 1456 of the UGT1A cDNA or 1459 of the UGT1D cDNA. These three mutations result in changes of glycine to arginine and of tyrosine to aspartic acid at amino acid positions 71 and 486 of the UGT1A protein, and of leucine to proline and of tyrosine to aspartic acid at amino acid positions 132 and 487 of the UGT1D protein, respectively. Our patient was homozygous for all defects and his parents and elder brother were heterozygous for all defective alleles. The findings suggest that the CN Type II is inherited as an autosomal recessive trait.

Expression of active human DNA ligase I in Escherichia coli cells that harbor a full-length DNA ligase I cDNA construct

A recombinant plasmid for expression of full-length human DNA ligase I (phLig-I) was constructed in a plasmid/phage chimeric vector, pTD-T7N, which was derived from pUC118 by oligonucleotide-directed mutagenesis. The insert contained a 2757-base pair coding sequence for a whole human DNA ligase I and an extra ACC codon adjacent to the ATG initiation codon. This ACC codon was required for achieving high levels of expression of full-length DNA ligase I in Escherichia coli strain BL21. The recombinant plasmid, which was designed to exploit the T7 late promoter and the ATG initiation codon for beta-galactosidase was transfected into E. coli BL21 cells that express T7 RNA polymerase. The recombinant clone produced relatively high levels of DNA ligase I with a molecular mass of 130 kDa, as estimated by SDS-polyacrylamide gel electrophoresis. The DNA ligase was purified to near-homogeneity by the two-step column chromatographic procedure from BLphLig-I cells that had been induced with isopropyl beta-D-thiogalactoside. The specific activity, chromatographic behavior, kinetic properties, molecular mass, and antigenicity of the recombinant human DNA ligase I were indistinguishable from those of purified mammalian DNA ligase I. Metabolically labeling experiments with 32P(i) indicate that the recombinant DNA ligase I was present as an enzyme-AMP reaction intermediate, but not as a phosphoprotein, in the E. coli cells.

Cloning of the mouse cDNA encoding DNA topoisomerase I and chromosomal location of the gene

The mouse cDNA encoding DNA topoisomerase I (TopoI) was cloned and the nucleotide sequence of 3512 bp was determined. The cDNA clone contained an open reading frame encoding a protein of 767 amino acids (aa), which is 2 aa longer than its human counterpart. Overall aa sequence homology between the mouse and human, and between the mouse and yeast (Saccharomyces cerevisiae) sequences was 96% and 42%, respectively. The mouse TopI gene was mapped at position 54.5 on chromosome 2 from linkage analyses of a three-point cross test with Geg, Ada, and a as marker genes.

[Genetic defect of the hyperbilirubinemic Gunn rat, a model for Crigler-Najjar syndrome type I]

The hyperbilirubinemic Gunn rat lacks hepatic UDP-glucuronosyltransferase (UDPGT) activity toward bilirubin and has been used as an animal model for human Crigler-Najjar syndrome type I. Rat liver bilirubin UDPGT cDNA was isolated. The cDNA shared an identical 913-bp sequence (corresponding to the C-terminal 247 amino acid residues) with that for phenol UDPGT whose activity was also deficient in the Gunn rat. The bilirubin UDPGT gene was mapped at the position of 37 on mouse chromosome 1 by analyzing restriction endonuclease fragment length variations using the rat bilirubin UDPGT cDNA as a probe. The genetic defect of bilirubin UDPGT in the mutant rat was proved to be a -1 frameshift mutation. The mutation was found not only to be located in the region where the cDNA for bilirubin UDPGT shared the identical sequence with that for phenol UDPGT but also to occur in the same position in the two cDNAs from the mutant.

Gastric procathepsin E and progastricsin from guinea pig. Purification, molecular cloning of cDNAs, and characterization of enzymatic properties, with special reference to procathepsin E

Procathepsin E and progastricsin were purified from the gastric mucosa of the guinea pig. They were converted to the active form autocatalytically under acidic conditions. Each active form hydrolyzed protein substrates maximally at around pH 2.5. Pepstatin inhibited cathepsin E very strongly at an equimolar concentration, whereas the inhibition was much weaker for gastricsin. Molecular cloning of the respective cDNAs permitted us to deduce the complete amino acid sequences of their pre-proforms; preprocathepsin E and preprogastricsin consisted of 391 and 394 residues, respectively. Procathepsin E has unique structural and enzymatic features among the aspartic proteinases. Lys at position 37, which is common to various aspartic proteinases and is thought to be important for stabilizing the activation segment, was absent at the corresponding position, as in human procathepsin E. The rate of activation of procathepsin E to cathepsin E is maximal at around pH 4.0. It is very different from the pepsinogens and may be correlated with the absence of Lys37. Native procathepsin E is a dimer, consisting of two monomers covalently bound by a disulfide bridge between 2 Cys37. Interconversion between the dimer and the monomer was reversible and regulated by low concentrations of a reducing reagent. Although the properties of the dimeric and monomeric cathepsins E are quite similar, a marked difference was found between them in terms of their stability in weakly alkaline solution: monomeric cathepsin E was unstable at weakly alkaline pH whereas the dimeric form was stable. The generation of the monomer was thought to be the process leading to inactivation, hence degradation of cathepsin E in vivo.

Mapping of the mouse bilirubin UDP-glucuronosyltransferase gene (Gnt-1) to chromosome 1 by restriction fragment length variations

Restriction endonuclease fragment length variations (RFLVs) were detected by using a rat cDNA probe for the bilirubin UDP-glucuronosyltransferase (UDPGT) gene between two mouse strains, 129/Sv and MOL-MIT. RFLVs of the gene were found by EcoRI and PvuII digestions. From linkage analyses of the three-point cross test using Elo and En-1 as marker genes, the bilirubin UDPGT gene was mapped at position 37 on chromosome 1. Bilirubin and phenol UDPGTs have been suggested to be expressed by a single gene by alternative splicing in human and rat. The mouse bilirubin UDPGT gene was named Gnt-1.

Cloning and sequencing of the cDNA encoding a mouse tissue inhibitor of metalloproteinase-2

A mouse cDNA encoding a tissue inhibitor of metalloproteinases (mTIMP-2) was cloned and the 1695-bp sequence was determined. While high homology was observed with the sequences encoding the human (hTIMP-2) and bovine (bTIMP-2) genes, mTIMP-2 contained a long 3'-nontranslated region not observed in the hTIMP-2 or bTIMP-2 genes.

Development-dependent expression of isozymogens of monkey pepsinogens and structural differences between them

The developmental changes in the expression of monkey pepsinogens and structural differences between the polypeptides were investigated. Monkey pepsinogens included five different components, namely, pepsinogens A-(1-4) and progastricsin. Their respective relative levels and specific activities changed significantly during development. The sequential expression of genes for type-A pepsinogens was particularly noteworthy. Pepsinogen A-3 was the major zymogen at the newborn stage, accounting for nearly half of the total pepsinogens at this stage. Pepsinogen A-2 became predominant at the 4-month stage, and pepsinogen A-1 predominated at the juvenile and adult stages. Enzymatic properties of pepsinogens A-1, A-2 and A-3 were similar but not identical to those of pepsinogen A-4 and progastricsin, in particular with respect to the activation processes. Each pepsin digested various protein substrates but some differences in specificity were evident. cDNA clones for five pepsinogens were isolated, and the nucleotide sequences were determined. Each cDNA contained leader, pro, and pepsin regions that encoded 15, 47, and 326 amino acid residues, respectively, with the exception of the cDNA for progastricsin in which the pro and pepsin regions encoded 43 and 329 amino acid residues, respectively. Type-A pepsinogens exhibited a high degree of similarity, with over 96% of bases in the nucleotide sequences of the protein-coding regions being identical. Northern analysis revealed that the level of expression of genes for type-A pepsinogens and for progastricsin was significant at the fetal stage and increased with development.

A molecular genetic linkage map of mouse chromosome 19, including the lpr, Ly-44, and Tdt genes

The mouse lpr gene, which is an autosomal recessive gene causing autoimmune disease with features of human systemic lupus erythematosus and eventually death from severe immune-complex glomerulonephritis, has been mapped on chromosome 19. To determine its exact chromosomal location, a three-point backcross was carried out by mating (MRL/MpJ-lpr/lpr x MOL-MIT)F1 x MRL/MpJ-lpr/lpr using the genes Ly-44 (lymphocyte differentiation antigen-44) and Tdt (terminal deoxynucleotidyl transferase) as markers. The following order of genes is proposed, with the distances between genes given in parentheses: centromere-Ly-44 (19.3 cM)-lpr (6.1 cM)-Tdt-telomere. The Ly-44a and Tdta alleles are found in all laboratory strains and in the wild Western European subspecies, domesticus and brevirostris. In contrast, the Ly-44b and Tdtb alleles are found in some Asian subspecies, Chinese mice of wild origin, yamashinai and molossinus. Furthermore the third Tdt allele, Tdtc, is detected in castaneus.

Genetic defect of bilirubin UDP-glucuronosyltransferase in the hyperbilirubinemic Gunn rat

The genetic defect of bilirubin UDP-glucuronosyltransferase (UDPGT) in the hyperbilirubinemic Gunn rat was proved to be a -1 frameshift mutation. The mutation was found not only to be located in the region where bilirubin UDPGT cDNA shared an identical sequence with 3-methylcholanthrene (3M C)-inducible UDPGT cDNA but also to occur in the same position on the two cDNAs from the mutant rat. At the 5' end of the identical region there was a consensus sequence for splicing, of which position coincided with the boundary between the 2nd and 3rd exon of the testosterone UDPGT gene. These results strongly suggest that mRNAs for bilirubin and 3M C-inducible UDPGTs are produced from a single primary-transcript after an alternative splicing and the defects of bilirubin and 3M C-inducible UDPGTs in the mutant rat are caused by a point mutation on a common exon.

Expression of terminal deoxynucleotidyltransferase gene in a case of adult T-cell leukemia

A 37-year-old male from Kagoshima Prefecture was admitted with adult T-cell leukemia (ATL). Monoclonal integration of HTLV-1 proviral DNA was found, but the integration site was different from that of terminal deoxynucleotidyltransferase (TdT)-positive MT-1 cells (an ATL cell line). The ATL cells expressed enzymatically active TdT and exhibited 2100 b TdT mRNA, which corresponds to the thymus type of TdT mRNA. The same size of TdT mRNA was also detected in MT-1. Southern blot analyses revealed no differences in the gene structure of the promoter region of TdT genes between this ATL case and TdT-positive lymphoblastic leukemia cells. There is little possibility that cis-acting viral elements promote TdT gene expression by proviral integration. The activation of TdT gene in ATL may be mediated by other trans-acting factors.

Molecular cloning of a cDNA of a camptothecin-resistant human DNA topoisomerase I and identification of mutation sites

Camptothecin (CPT), a plant alkaloid with antitumor activity, is a specific inhibitor of eukaryotic DNA topoisomerase I. We have previously isolated and characterized a CPT-resistant topoisomerase I isolated from a CPT-resistant human leukemia cell line, CPT-K5. cDNA clones of topoisomerase I were isolated from the CPT-resistant and the parental CPT-sensitive cell lines, respectively. Sequencing of the clones identified two mutations in the cDNA isolated from the resistant cells, which cause amino acid changes from aspartic acid to glycine at residues 533 and 583 of the parental topoisomerase I. When the CPT-K5 topoisomerase I was expressed in E. coli as a fusion protein with Staphylococcal Protein A fragment, the activity was resistant to CPT at a dose level up to 125 microM, whereas the parental fusion protein was sensitive to CPT as low as 1 microM. The resistance index (greater than 125) of the CPT-K5 fusion topoisomerase I is similar to that of the native CPT-K5 topoisomerase I. These results indicate that either or both of the two amino acid changes identified in the mutant enzyme is responsible for the resistance to CPT.

Structure and development of rabbit pepsinogens. Stage-specific zymogens, nucleotide sequences of cDNAs, molecular evolution, and gene expression during development

In order to clarify the structure and development of rabbit pepsinogens, purification and molecular cloning of these proteins were performed at various developmental stages. Several pepsinogens were isolated, and they were classified as pepsinogens F and M, and into pepsinogen groups I, II, and III. The relative levels and specific activities of the various pepsinogens changed significantly during development. Pepsinogens F and M were present only at the early postnatal stage, and their level was higher than those of other pepsinogens at this stage. Pepsinogens in groups I, II, and III were the predominant zymogens at the late postnatal stage. cDNA clones encoding all of these pepsinogens were obtained, with the exception of pepsinogens I and M, and the nucleotide sequences were determined. Each cDNA contained a leader region (signal peptide), a pro-region (activation segment), and a pepsin region, of 15, 44, and 328 residues, respectively, with the exception of the cDNA for pepsinogen F in which the pro- and pepsin regions were composed of 43 and 330 residues, respectively. Pepsinogens in groups II and III exhibited a high degree of similarity with one another, whereas many substitutions were found in pepsinogen F. A unique substitution in the activation segment of pepsinogen F, namely, Gly----Asp at position 21, was found, which made the structural features of this segment more specific. A phylogenic tree was constructed from the differences in nucleotide sequences and showed clearly that each pepsinogen in groups II and III could be classified as pepsinogen A, a major pepsinogen in mammals. Pepsinogen F diverged significantly from these groups and may be a new type of pepsinogen. Northern analysis revealed that the expression of the gene for pepsinogen F was restricted to the early postnatal stage, and the expression of genes for pepsinogens in groups II and III was detected predominantly at later stages, a result that shows the switching of gene expression from fetal pepsinogen to adult pepsinogens during development.

Isolation and sequencing of rat liver bilirubin UDP-glucuronosyltransferase cDNA: possible alternate splicing of a common primary transcript

A 1763-bp cDNA for rat liver bilirubin UDP-glucuronosyltransferase (UDPGT) was isolated. Bilirubin UDPGT activity was demonstrated by transfection of the pcDL1 vector carrying the cDNA into COS7 monkey kidney cells. The cDNA shares an identical 913-bp sequence (corresponding to the C-terminal 247 amino acid residues) with that for rat liver 3-methylcholanthrene-inducible 4-nitrophenol UDPGT including the locus where a -1 frameshift mutation was found in the 4-nitrophenol UDPGT cDNA from the jaundiced homozygous Gunn rat. The result suggests that both the UDPGTs are derived from a common primary-transcript and that the multiple defects of UDPGT isoenzymes observed in the homozygous Gunn rat may be produced by a single-mutated-locus after an alternative splicing of the 5' end region.

Demonstration of promoter function for the 5'-flanking region of the human gene for terminal deoxynucleotidyl transferase

Promoter activity was detected by transfection of pBS vectors that carried the 5'-flanking region of the gene for human terminal deoxy-nucleotidyltransferase (TdT) and the entire human TdT cDNA into COS7 monkey kidney cells, with direct assay of the expressed enzymatically active TdT. The synthesis of TdT was also detected immunologically using polyclonal rabbit antibodies against bovine TdT. One fifth of the TdT activity detected in normal thymocytes was detected in transfected COS7 cells. This results suggests that a lymphoid-specific regulatory system is present in B or T-cells to promote the effective expression of TdT.

Gene expression of terminal deoxynucleotidyl transferase in neoplastic cells of leukemia and lymphoma

Expression levels of terminal deoxynucleotidyl transferase (TdT) mRNA in fresh leukemia and lymphoma cells were measured by northern blotting analysis. Bands of 2.1 kb mRNA were detected in all of eight cases of TdT activity-positive leukemias: two cases of null-cell acute lymphoblastic leukemia (null-ALL), two of common ALL, one of pre-B ALL, one of T-ALL, and two of chronic myelogenous leukemia in blastic crisis. One of the null-ALL and one of the common ALL cases also showed large TdT mRNA (3.3 kb). Since all TdT activity-positive samples exhibited TdT mRNA, the TdT gene might be mainly regulated at the transcription level in leukemic cells. An elevated level of 2.1 kb TdT mRNA was also detected in one lymphoma case, where neither TdT activity nor immunoreactive TdT was detected. The extensive chromosomal abnormality demonstrated in this case might be associated with the translational anomaly of TdT.

Isolation of putative promoter region for human terminal deoxynucleotidyltransferase gene

We have isolated the genomic clone, which contained 5'-flanking region for human terminal deoxynucleotidyltransferase (TdT) gene, by screening Charon 4A library and determined its nucleotide sequence. Two transcription initiation sites (cap sites) were localized at 81 and 106 bp upstream from the third ATG codon which is translation initiation site, by primer extension analysis. Although neither typical TATA nor CAAT sequences were detected within 100 bp upstream region of the 5' cap site, a palindromic structure comprised of 28 bp was formed just upstream of the 5' cap site and double repeats of 5'-CTGGC sequence were found in its palindrom. The typical octamer of 5'-ATGCAAAT and three octamer-like sequences, which are involved in the transcription of lymphoid-specific genes, were detected at 212, 293, 347 and 770 bp upstream from the first cap site.

Analysis of human terminal deoxynucleotidyl transferase cDNA expressible in mammalian cells

Human Molt3 cDNA library was constructed using pcD vector system which permits the expression of cDNA inserts in mammalian cells. Nearly full-length human terminal deoxynucleotidyltransferase (TdT) cDNA was cloned using a fragment of bovine TdT cDNA as a probe. The human TdT cDNA contains an open reading frame of 1,557 bp coding for 519 amino acids, including 31 bp and 341 bp from 5' and 3' untranslated regions, respectively. The TdT cDNA was transfected into COS7 monkey fibroblasts directed the synthesis of enzymatically active protein of Mr 59,495. The cloned TdT cDNA hybridized with poly A+ RNAs of 2,100 b and 3,300 b from stable T-cell leukemia Molt3 and Molt4 cells.

Isolation and characterization of bovine and mouse terminal deoxynucleotidyltransferase cDNAs expressible in mammalian cells

We have isolated nearly full-length cDNA clones of terminal deoxynucleotidyltransferase (TdT) from calf thymus and mouse lymphoma cDNA libraries. The libraries were constructed using the pcD vector system which permits the expression of cDNA inserts in mammalian cells. The bovine TdT cDNA clone contains an open reading frame coding for 520 amino acids, Mr 59,678. The mouse TdT cDNA clone contains an open reading frame of 1,587 bp, whose translated cDNA encodes a 60,004 dalton protein. The mouse TdT cDNA clone contains 60 bp in the 3' end region of the coding sequence not found in the bovine TdT cDNA sequence, otherwise, the clones share about 80% homology. A possible nuclear-localization-sequence (Pro-Arg-Lys-Lys-Arg-Pro-Arg) was conserved in the N-terminal region in the mouse and bovine cDNA clones. Bovine and mouse cDNAs transfected into COS7 monkey fibroblasts directed the synthesis of enzymatically active protein of Mr 60,000 which was detected immunologically using polyclonal rabbit antibody against bovine TdT. Bovine TdT expressed in COS7 cells by nearly full-length cDNA clone was localized in the nucleus and the translational product of pOK103 lacking the nuclear-localization-sequence was localized in the cytoplasm.

Characterization of DNA primase separated from DNA polymerase alpha-DNA primase complex of calf thymus

It has been shown that DNA primase activity is tightly associated with 10S DNA polymerase alpha from calf thymus (Yoshida, S. et al. (1983) Biochim. Biophys. Acta 741, 348-357). In the present study, the primase activity was separated from DNA polymerase alpha by treating purified 10S DNA polymerase alpha with 3.4 M urea followed by a fast column chromatography (Pharmacia FPLC, Mono Q column equilibrated with 2 M urea). Ten to 20 % of the primase activity was separated from 10S DNA polymerase alpha by this procedure but 80-90% remained in the complex. The separated primase activity sedimented at 5.6S through a gradient of glycerol. The separated primase was strongly inhibited by araATP (Ki = 10 microM) and was also sensitive to salts such as KCl (50% inhibition at 30 mM). The primase used poly(dT) or poly(dC) as templates efficiently, but showed little activity with poly(dA) or poly(dI). These properties agree well with those of the primase activity in the DNA polymerase alpha-primase complex (10S DNA polymerase alpha). These results indicate that the calf thymus primase may be a part of the 10S DNA polymerase alpha and its enzymological characters are preserved after separation from the complex.

Arabinosylnucleoside 5'-triphosphate inhibits DNA primase of calf thymus

It has been shown that DNA primase activity is tightly associated with 10S DNA polymerase alpha from calf thymus and that the ribonucleotide-dependent DNA synthesis is more sensitive to araCTP than DNA-primed DNA synthesis (Yoshida, S., et al. (1983) Biochim. Biophys. Acta 741, 348-357). Here we measured DNA primase activity using poly(dT) template or M13 bacteriophage single-stranded DNA template and primer RNA synthesis was coupled to the reaction by Escherichia coli DNA polymerase I Klenow fragment. By this method, the primer RNA synthesis can be measured independently of the associating DNA polymerase alpha. Using poly(dT) template, it was found that arabinosyladenine 5'-triphosphate (araATP) strongly inhibited DNA primase in competition with rATP. The apparent Ki for araATP was 21 microM and the ratio of Ki/Km (for rATP) was as low as 0.015. With poly(dI, dT) or M13 DNA, it was shown that araCTP also inhibited DNA primase in the similar manner. Product analysis using [alpha-32P]rATP showed that araATP inhibited the elongation of primer RNA. However, it is not likely that arabinosylnucleotides act as chain-terminators, since incubation of primer RNA with araATP did not abolish its priming activity. From these results, it is suggested that arabinosylnucleotide inhibits the initiation as well as elongation of Okazaki fragments in mammalian cells.

Arrest of DNA elongation by DNA polymerases at guanine adducts on 4-hydroxyaminoquinoline 1-oxide-modified DNA template

In vitro modification of M13 phage single-stranded DNA with 4-hydroxyaminoquinoline 1-oxide (4HAQO) resulted in four kinds of adducts: three guanine adducts, QGI, QGII, and QGIII; and one adenine adduct, QA, at ratios of 16.4 47.3, 13.7, and 22.6, respectively. The carcinogen-modified DNA, initiated with a sequence-defined oligodeoxynucleotide primer, was replicated in vitro with Escherichia coli DNA polymerase I (Klenow fragment) and calf thymus DNA polymerases alpha and beta. The reaction products were analyzed on a DNA-sequencing gel. DNA elongation by DNA polymerase I was arrested at putative guanine adducts on the template in three ways: at one base prior to guanine; at positions opposite to guanine; and at one base beyond guanine. Similar patterns of elongation arrest were also obtained with the mammalian DNA polymerases alpha and beta. In contrast to guanine adducts, the adenine adduct, QA, might lack the capacity to arrest DNA chain elongation by DNA polymerases.

DNA primase associated with 10 S DNA polymerase alpha from calf thymus

Among multiple subspecies of DNA polymerase alpha of calf thymus, only 10 S DNA polymerase alpha had a capacity to initiate DNA synthesis on an unprimed single-stranded, circular M13 phage DNA in the presence of ribonucleoside triphosphates (DNA primase activity). The primase was copurified with 10 S DNA polymerase alpha through the purification and both activities cosedimented at 10 S through gradients of either sucrose or glycerol. Furthermore, these two activities were immunoprecipitated at a similar efficiency by a monoclonal antibody directed against calf thymus DNA polymerase alpha. These results indicate that the primase is tightly bound to 10 S DNA polymerase alpha. The RNA polymerizing activity was resistant to alpha-amanitin, required high concentration of all four ribonucleoside triphosphates (800 microM) for its maximal activity, and produced the limited length of oligonucleotides (around 10 nucleotides long) which were necessary to serve as a primer for DNA synthesis. Covalent bonding to RNA to DNA was strongly suggested by the nearest neighbour frequency analysis and the DNAase treatment. The DNA synthesis primed by the RNA oligomers may be carried out by the associating DNA polymerase alpha because it was strongly inhibited by araCTP, resistant to d2TTP, and was also inhibited by aphidicolin but at relatively high concentration. The primase preferred single-stranded DNA as a template, but it also showed an activity on the double-stranded DNA from calf thymus at an efficiency of approx. 10% of that with single-stranded DNA.

Production and characterization of monoclonal antibody against 10S DNA polymerase alpha from calf thymus

One hybridoma cell line that produces an antibody directed against 10S DNA polymerase alpha purified from calf thymus was obtained. The monoclonality of the antibody was tested by sodium dodecyl sulfate polyacrylamide gel electrophoresis, isoelectrofocusing and antibody subclass determination. The antibody specifically recognized the 10S DNA polymerase alpha and 6.5S DNA polymerase alpha-2 from calf thymus, but not 6.5S DNA polymerase alpha-1. The antibody precipitated both polypeptides of 140-150,000 and 46-50,000 dalton of 10S DNA polymerase alpha. The antibody also recognized the DNA polymerase alpha purified from human cells, but did pig DNA polymerase alpha only partially. The antibody did not crossreact with rat DNA polymerase alpha, calf DNA polymerase beta, virus DNA polymerase and E. coli DNA polymerase I. This antibody will be a useful tool for studying the mechanism of DNA replication in eukaryotic cells.

Analysis of calf thymus DNA polymerases alpha and beta and terminal deoxynucleotidyl transferase on two-dimensional polyacrylamide gels

Calf thymus DNA polymerases alpha and beta [EC 2.7.7.7] and terminal deoxynucleotidyl transferase [EC 2.7.7.31] were analyzed on two-dimensional gel slabs. DNA polymerase beta appeared as a single spot on two-dimensional gel at the position of 40,000 daltons and pI 8.0 using non-equilibrium pH gradient gel electrophoresis for the first-dimensional run. By overlapping gel slabs, it was possible to identify the distinct spot of DNA polymerase beta among many polypeptide spots of a crude enzyme fraction. 10S DNA polymerase alpha showed two clusters of polypeptide spots on two-dimensional gel slab. One cluster was composed of three large polypeptides of 140,000-150,000 daltons and another was composed of four smaller polypeptides of 46,000-50,000 daltons. All these spots were arranged in a narrow pI range (6.5-6.8) although each spot showed a distinct pI value. Purified terminal deoxynucleotidyl transferase showed three polypeptides of 57,000, 42,000, and 33,000 daltons at similar pI values (7.0-7.2). Each polypeptide consisted of plural spots which differed slightly in pI but were the same in molecular weight. These results suggest a microheterogeneity of polypeptides of terminal deoxynucleotidyl transferase as well as those of 10S DNA polymerase alpha.