[Pneumatic external counterpulsation--a therapy option in angina pectoris]

Pneumatic external counterpulsation operates by applying ECG-triggered diastolic pressure via cuffs to the vascular bed of the lower limbs. Comparable with intra-aortic balloon pumping, PECP produces a diastolic augmentation combined with increase of mean arterial pressure and coronary perfusion. American, Asian, and our own data demonstrated a reduction of angina pectoris through repeated use of PECP one or two hours daily for four to seven weeks. Exercise testing and thallium scanning confirmed the clinical improvement. PECP is a virtually risk-free treatment option in patients suffering from angina despite medical and interventionell treatment. Opening of collaterals and collateral growth induced by external counterpulsation are discussed as the cause of clinical benefit.

DNA end-independent activation of DNA-PK mediated via association with the DNA-binding protein C1D

DNA-dependent protein kinase (DNA-PK), which is involved in DNA double-strand break repair and V(D)J recombination, is comprised of a DNA-targeting component termed Ku and an approximately 465-kD catalytic subunit, DNA-PKcs. Although DNA-PK phosphorylates proteins in the presence of DSBs or other discontinuities in the DNA double helix in vitro, the possibility exists that it is also activated in other circumstances via its association with additional proteins. Here, through use of the yeast two-hybrid screen, we discover that the recently identified high affinity DNA binding protein C1D interacts with the putative leucine zipper region of DNA-PKcs. Furthermore, we show that C1D can interact with DNA-PK in mammalian cells and that C1D is a very effective DNA-PK substrate in vitro. Finally, we establish that C1D directs the activation of DNA-PK in a manner that does not require DNA termini. Therefore, these studies provide a function for C1D and suggest novel mechanisms for DNA-PK activation in vivo.

Genotypic characterization of Bradyrhizobium strains nodulating endemic woody legumes of the Canary Islands by PCR-restriction fragment length polymorphism analysis of genes encoding 16S rRNA (16S rDNA) and 16S-23S rDNA intergenic spacers, repetitive extragenic palindromic PCR genomic fingerprinting, and partial 16S rDNA sequencing

We present a phylogenetic analysis of nine strains of symbiotic nitrogen-fixing bacteria isolated from nodules of tagasaste (Chamaecytisus proliferus) and other endemic woody legumes of the Canary Islands, Spain. These and several reference strains were characterized genotypically at different levels of taxonomic resolution by computer-assisted analysis of 16S ribosomal DNA (rDNA) PCR-restriction fragment length polymorphisms (PCR-RFLPs), 16S-23S rDNA intergenic spacer (IGS) RFLPs, and repetitive extragenic palindromic PCR (rep-PCR) genomic fingerprints with BOX, ERIC, and REP primers. Cluster analysis of 16S rDNA restriction patterns with four tetrameric endonucleases grouped the Canarian isolates with the two reference strains, Bradyrhizobium japonicum USDA 110spc4 and Bradyrhizobium sp. strain (Centrosema) CIAT 3101, resolving three genotypes within these bradyrhizobia. In the analysis of IGS RFLPs with three enzymes, six groups were found, whereas rep-PCR fingerprinting revealed an even greater genotypic diversity, with only two of the Canarian strains having similar fingerprints. Furthermore, we show that IGS RFLPs and even very dissimilar rep-PCR fingerprints can be clustered into phylogenetically sound groupings by combining them with 16S rDNA RFLPs in computer-assisted cluster analysis of electrophoretic patterns. The DNA sequence analysis of a highly variable 264-bp segment of the 16S rRNA genes of these strains was found to be consistent with the fingerprint-based classification. Three different DNA sequences were obtained, one of which was not previously described, and all belonged to the B. japonicum/Rhodopseudomonas rDNA cluster. Nodulation assays revealed that none of the Canarian isolates nodulated Glycine max or Leucaena leucocephala, but all nodulated Acacia pendula, C. proliferus, Macroptilium atropurpureum, and Vigna unguiculata.

Release of flavonoids by the soybean cultivars McCall and peking and their perception as signals by the nitrogen-fixing symbiont sinorhizobium fredii

Sinorhizobium fredii strain USDA191 forms N-fixing nodules on the soybean (Glycine max L. Merr.) cultivars (cvs) McCall and Peking, but S. fredii strain USDA257 nodulates only cv Peking. We wondered whether specificity in this system is conditioned by the release of unique flavonoid signals from one of the cultivars or by differential perception of signals by the strains. We isolated flavonoids and used nodC and nolX, which are nod-box-dependent and -independent nod genes, respectively, to determine how signals activate genes in the microsymbionts. Seeds of cv McCall and cv Peking contain the isoflavones daidzein, genistein, and glycitein, as well as their glucosyl and malonylglucosyl glycosides. Roots exude picomolar concentrations of daidzein, genistein, glycitein, and coumestrol. Amounts are generally higher in cv Peking than in cv McCall, and the presence of rhizobia markedly influences the level of specific signals. Nanomolar concentrations of daidzein, genistein, and coumestrol induce expression of nodC and nolX in strain USDA257, but the relative nolX-inducing activities of these signals differ in strain USDA191. Glycitein and the conjugates are inactive. Strain USDA257 deglycosylates daidzin and genistin into daidzein and genistein, respectively, thereby converting inactive precursors into active inducers. Although neither soybean cultivar contains unique nod-gene-inducing flavonoids, strain- and cultivar-specific interactions are characterized by distinct patterns of signal release and response.

cDNA cloning, recombinant expression and characterization of polypetides with exceptional DNA affinity

Polypeptides remaining tightly associated with isolated genomic DNA are of interest with respect to their potential involvement in the topological organization and/or function of genomic DNA. Such residual DNA-polypeptide complexes were used for raising monoclonal antibodies by in vitro immunization. Screening of a murine lambdagt11 cDNA library with these antibodies released a positive cDNA (MC1D) encoding a 16 kDa polypeptide. The cloned homologous human cDNA (HC1D) was identified in the dbest data base by partial sequence comparison, and it was sequenced full length. The cDNA-derived amino acid sequences comprise nuclear location signals but none of the known DNA-binding motifs. However, the recombinantly expressed proteins show in vitro DNA binding affinities. A polyclonal antiserum to the recombinant MC1D protein immunostains sub-nuclear structures, and it detects a residual 16 kDa polypeptide on western blots of DNA digests. These results support the conclusion that the cloned cDNAs reflect mRNAs encoding one of the chemically-resistant polypeptides which can be detected in isolated genomic DNA by sensitive techniques, e.g. by125Iodine labeling and SDS-PAGE.

A plant homolog of the neutrophil NADPH oxidase gp91phox subunit gene encodes a plasma membrane protein with Ca2+ binding motifs

Rapid generation of O2- and H2O2, which is reminiscent of the oxidative burst in neutrophils, is a central component of the resistance response of plants to pathogen challenge. Here, we report that the Arabidopsis rbohA (for respiratory burst oxidase homolog A) gene encodes a putative 108-kD protein, with a C-terminal region that shows pronounced similarity to the 69-kD apoprotein of the gp91phox subunit of the neutrophil respiratory burst NADPH oxidase. The RbohA protein has a large hydrophilic N-terminal domain that is not present in gp91phox. This domain contains two Ca2+ binding EF hand motifs and has extended similarity to the human RanGTPase-activating protein 1. rbohA, which is a member of a divergent gene family, generates transcripts of 3.6 and 4.0 kb that differ only in their polyadenylation sites. rbohA transcripts are most abundant in roots, with weaker expression in aerial organs and seedlings. Antibodies raised against a peptide near the RbohA C terminus detected a 105-kD protein that, unlike gp91phox, does not appear to be highly glycosylated. Cell fractionation, two-phase partitioning, and detergent extraction indicate that RbohA is an intrinsic plasma membrane protein. We propose that plants have a plasma membrane enzyme similar to the neutrophil NADPH oxidase but with novel potential regulatory mechanisms for Ca2+ and G protein stimulation of O2- and H2O2 production at the cell surface.

A plant homolog of the neutrophil NADPH oxidase gp91phox subunit gene encodes a plasma membrane protein with Ca2+ binding motifs

Rapid generation of O2- and H2O2, which is reminiscent of the oxidative burst in neutrophils, is a central component of the resistance response of plants to pathogen challenge. Here, we report that the Arabidopsis rbohA (for respiratory burst oxidase homolog A) gene encodes a putative 108-kD protein, with a C-terminal region that shows pronounced similarity to the 69-kD apoprotein of the gp91phox subunit of the neutrophil respiratory burst NADPH oxidase. The RbohA protein has a large hydrophilic N-terminal domain that is not present in gp91phox. This domain contains two Ca2+ binding EF hand motifs and has extended similarity to the human RanGTPase-activating protein 1. rbohA, which is a member of a divergent gene family, generates transcripts of 3.6 and 4.0 kb that differ only in their polyadenylation sites. rbohA transcripts are most abundant in roots, with weaker expression in aerial organs and seedlings. Antibodies raised against a peptide near the RbohA C terminus detected a 105-kD protein that, unlike gp91phox, does not appear to be highly glycosylated. Cell fractionation, two-phase partitioning, and detergent extraction indicate that RbohA is an intrinsic plasma membrane protein. We propose that plants have a plasma membrane enzyme similar to the neutrophil NADPH oxidase but with novel potential regulatory mechanisms for Ca2+ and G protein stimulation of O2- and H2O2 production at the cell surface.

Distribution of 14C-TNT and derivatives in different biochemical compartments of Phaseolus vulgaris

(14)C-TNT was used to quantify the uptake rate and metabolic turnover of TNT in Phaseolus vulgaris. Seventeen plants were analysed by a special cell fractionation method with polar and nonpolar solvents and enzymes. We obtained three cytoplasmic fractions and five cell wall derived fractions. The recovery rate was 72% as measured by liquid scintillation counting. (14)C partitioned almost in equal amounts with approximately 50% in the cytoplasm and in the cell wall. The majority of the TNT-metabolites are present in the cytoplasm as was shown by GC/ECD and thin layer chromatography. The(14)C in the cell wall is bound probably resulting in long-term immobilisation of these metabolites. We conclude that plants may also be a model for nitroaromatic turnover and immobilisation in soil components.

The centrosomal protein centrosomin A and the nuclear protein centrosomin B derive from one gene by post-transcriptional processes involving RNA editing

The identification of a gene encoding concomitantly a nuclear protein and an intrinsic centrosomal protein further emphasizes the close and presumably developmental relationship between the cell nucleus and the centrosome. Screening of a murine RNA-based cDNA library with an antiserum to a centrosomal protein and rescreening with the insert of an initial clone released two complete cDNAs (1.2 kbp and 2.2 kpb) coding for proteins with notable characteristics. The amino-terminal sections of centrosomin A (276 amino acid residues, molecular mass 34.5 kDa) and of centrosomin B (447 amino acid residues, molecular mass 54.8 kDa) are identical over 272 amino acid residues. The carboxy-terminal section of the larger protein comprises additional 175 amino acid residues including nuclear location signals. The mRNAs encoding centrosomin A and B derive from a single gene. Chromogenomic DNA as template and primer pairs complementary to the sequence which is identical in centrosomin A and B cDNAs results in amplification of only one DNA fragment. Moreover, one exon of the genomic sequence and the centrosomin B-encoding cDNA sequence include a G which is deleted in the centrosomin A-encoding cDNA. Accordingly, the two mRNAs are the products of either alternative splicing or alternative polyadenylation in combination with RNA editing. The recombinantly expressed chimeric protein consisting of centrosomin A and the green fluorescent protein from Aequorea victoria accumulates in centrosomes while the corresponding fusion protein with the centrosomin B sequence is transported into nuclei.

Cationic polyhexylcyanoacrylate nanoparticles as carriers for antisense oligonucleotides

After antisense oligodeoxynucleotides (ODNs) were suggested for therapeutic use in 1978, major advances were made in developing modified oligonucleotides with increased nuclease resistance and improved cellular uptake. In the present report, positively charged nanoparticles prepared from diethylaminoethyl (DEAE)-dextran and polyhexylcyanoacrylate (PHCA) were evaluated as carriers for ODNs. The oligonucleotides were analyzed by anion-exchange HPLC. The nanoparticles exhibited a high loading capacity, with approximately 35 mumol ODNs adsorbed per gram of polymeric material. The adsorption efficacy was found to be dependent on the pH, on the ionic strength of the medium, and on the amount of DEAE-dextran. Highest loading for ODNs was achieved at pH 5.5, using a 10 mM phosphate buffer. Oligonucleotides adsorbed to the surface of the nanoparticles were nearly completely protected against degradation by the endonuclease DNase I and under in vitro cell culture conditions, whereas unprotected ODNs were totally digested under these conditions. Nanoparticles led to a 20-fold increase in cellular uptake of FITC-oligonucleotides. The internalized oligonucleotides were frequently localized as vesicular structures in the cytoplasmatic compartment. Because of their temperature-dependent uptake, we propose an active uptake mechanism, such as endocytosis, for the internalization of the ODN-nanoparticle formulations.

A multifunctional protein: involvement of the alpha-1 serum protease inhibitor in SDS and high salt-stable DNA-protein complexes

Occasionally new and intriguing roles arise for proteins with well established functions. The alpha-1 serum protease inhibitor (alpha-1 PI) represents another example. Sequence identities exist in the alpha-1 PI and in a nuclear 52-kDa glycoprotein which is involved in resistant DNA-polypeptide complexes. The results of Western blots support the identity of the two proteins and immunocytochemical studies indicate the nuclear location of the alpha-1 PI. Consistently, e.g. Ehrlich ascites tumor cells express the alpha-1 PI, and the fusion protein between the alpha-1 PI and the green fluorescent protein from Aequorea victoria shows intracellular accumulation and partly nuclear location.

Mapping of G2/M-phase prevalences of chaperon-encoding transcripts by means of a sensitive differential hybridization approach

The sensitivity of the differential hybridization approach is significantly increased by the application of size-selected probes. RNA from elutriated phase-synchronous Ehrlich ascites tumor (EAT) cells has previously been used to prepare cell cycle phase-specific cDNA libraries in the in-vitro transcription vector pBluescript. PCR amplification of the libraries with vector-fitting primer pairs generates amplified cDNA reflecting the mRNA complexities of cells in G1, S and G2/M phases. Probes with reduced complexities were recovered after side-by-side electrophoresis of equal amounts of PCR-amplified cDNA and elution of probes from parallel gel sections. Such size-selected probes release significant differential clones which escape their detection in the conventional differential hybridization approach. Three clones hybridizing preferentially with the G2/M phase-specific probe were further characterized. The genes were identified by their nucleotide sequences. They encode proteins known to be involved in protein folding: heatshock cognate protein, HSC 70; heatshock cognate protein, HSC 73; eta subunit of the chaperonin containing TCP-1 complex, CCT. The G2/M phase-prevalent expression of these genes were further verified on the mRNA and on the protein level by Northern and Western blot analysis which confirms the significance of the differential hybridization approach and which indicates that the expression of this group of proteins increases with cell cycle progression. The expression of the chaperonin-containing TCP-1 complex appears to be specifically linked with the S to G2/M phase transition of the cell cycle.

Restriction Analysis of PCR-Amplified Internal Transcribed Spacers of Ribosomal DNA as a Tool for Species Identification in Different Genera of the Order Glomales

A technique combining PCR and restriction fragment length polymorphism analysis was used to generate specific DNA fragment patterns from spore extracts of arbuscular mycorrhizal fungi. With the universal primers ITS1 and ITS4, DNA fragments were amplified from species of Scutellospora and Gigaspora that were approximately 500 bp long. The apparent lengths of the corresponding fragments from Glomus spp. varied between 580 and 600 bp. Within the genus Glomus, the restriction enzymes MboI, HinfI, and TaqI were useful for distinguishing species. Depending on the restriction enzyme used, groups of species with common fragment patterns could be found. Five tropical and subtropical isolates identified as Glomus manihotis and G. clarum could not be distinguished by their restriction patterns, corresponding to the morphological similarity of the spores. The variation of internal transcribed spacer sequences among the Gigaspora species under study was low. Fragment patterns of Scutellospora spp. showed their phylogenetic relationship with Gigaspora and revealed only a slightly higher degree of variation.

Molecular cloning of a cDNA encoding an antigen which is salt-stably attached to centrosomes

A monoclonal antibody (MAB 2A8) was used for expression-cloning of a complete cDNA (1133/5) to a mRNA (3 kb) encoding a murine 76 kDa polypeptide. The N-terminal section of the polypeptide is composed of domains capable to form alpha-helical coiled-coils. Its C-terminus is proline-rich and has characteristics of the Src homology region 3 (SH3). Affinity-purified antibodies to a recombinant section of the protein show that the antigen is salt-stably associated with the centrosome throughout the cell cycle.

Characterization of the imprinted IPW gene: allelic expression in normal and tumorigenic human tissues

IPW (Imprinted gene in the Prader-Willi syndrome region) is a recently identified paternally expressed gene. Previous work has demonstrated IPW expression in the human fetus and adult, with monoallelic expression in adult lymphoblasts and fibroblasts, and in fetal tissues. To further examine the expression of IPW, a series of experiments were carried out using RT-PCR to measure IPW expression in placentae and various fetal and tumor tissues. Biallelic expression of IPW was found in testicular germ cell tumor and bladder cancer cells, suggesting loss of imprinting in the latter case. Both H19 and Insulin-like growth Factor 2 (IGF2), two additional imprinted genes, also showed biallelic expression in those same tumors that demonstrated IPW biallelic expression. Of note, the naturally occurring parthenogenetic-derived mature teratoma unexpectedly expressed large amounts of IPW. Lastly, the pluripotent embryonal cancer cell line Tera-2 expressed IPW at the same level before and after differentiation induced by retinoic acid, suggesting that this gene functions in a 'housekeeping' capacity throughout cell growth. This was in contradistinction to H19 and IGF2, both of which showed significant transcriptional upregulation after Tera-2 cell differentiation.

Activation and enzyme characteristics of a DNA-restrained phosphatase in chromatin-associated complexes

DNA-bound polypeptide complexes composed of several non-histone polypeptides that resisted harsh DNA deproteinization procedures were characterized. The three major polypeptides of these complexes have molecular masses of 62, 52, and 40 kDa. They constitute supramolecular structures that reside on isolated DNA in dense clusters. The supramolecular complexes were released from DNA as globular 12.8 +/- 0.8-nm particles; these particles were gradually disassembled to form smaller supramolecular structures. The DNA-bound complexes comprise of an encrypted adenosinetriphosphatase/phosphatase activity, which is a minor but intrinsic component of the complexes. The enzyme remained inactive as long as the complexes were bound to DNA. However, the enzyme was activated concomitantly with the progression of DNA digestion, which indicated that DNA was involved in the downregulation of the enzyme. The inactive DNA-restrained complex could not be restored in vitro, which indicated its non-trivial nature. Once released from DNA, the enzyme was inactivated over a period of several hours. However, in the DNA-associated complexes its potential to become activated during DNA digestion was conserved for several months. In the activated state, the enzyme showed an optimum activity at pH 9.5, was stimulated by Mg2+, inhibited by vanadate and EDTA, but was not significantly inhibited by okadaic acid. The active enzyme, which consists of two subunits of 56 kDa and 59 kDa, can be released from the supramolecular structures by agarose gel electrophoresis. A regulatory mechanism therefore exists for the downregulation of this phosphatase by DNA.

Expression of DMAP-45R in the rat visual cortex is modulated by visual experience

Effects of visual experience upon expression of a developmentally regulated microtubule-associated protein (MAP) were studied in the visual cortex of monocularly deprived rats. The antibody Drosophila MAP-45 (DMAP-45) recognizes proteins in the developing ventral nerve cord of Drosophila and in rat brain. Monocular deprivation from day 12, before eye opening, to day 80 reduced the number of DMAP-45 immunoreactive layer V pyramidal cell apical dendrites in the monocular segment (Oc1M) of the visual cortex contralateral to the deprived eye. No significant visual deprivation effects were seen in the binocular segment (Oc1B). Immunoreactivity was restored to control levels in Oc1M of rats in which the monocular sutures were removed at day 75, subsequently allowing 5 days of exposure to light. These results indicate potential involvement of this MAP in experience-dependent structural plasticity.

[Imprints of coronary plaque particles in the PTCA balloon surface during the dilatation processing]

Seventy-six PTCA-balloons after coronary angioplasty were studied for superficial changes using scanning electron microscopy (SEM) after fixing in glutardialdehyde. Coronary plaque particles were identified on the balloon surface in 52 cases (68%). Twelve new and unused balloons were subjected to the same chemical treatment and SEM showed no imprints. The average length of the longest imprinted plaques was 128 +/- 201 microns and the average number of plaque particles per balloon was 4.9 +/- 2.7. The maximal dilatation pressure and the number of dilatations showed no influence on the impregnation of plaque particles. However, longer plaque imprints tended to occur under low dilatation pressure. Imprints of plaque particles were significantly higher in patients with low cholesterol (p = 0.0001) and low triglycerides (p = 0.0016). No correlation was seen between imprint length and lipid levels. Similarly, the different balloon materials (polyethylene, polyolefincopolymer) showed no significant differences with regard to plaque occurrence. The PTCA-balloons, plaque particles and six coronary plaques obtained after endatherectomy were subjected to energy dispersive x-ray analysis (EDX) under SEM as EDX reveals qualitative and quantitative information about the structural elements. Highly significant differences in calcium, sodium, phosphorus and silicon contents (p = 0.0000) between plaque particles and balloon surface were observed, owing to the absence of these in balloon material. Thus EDX offers additional advantages over SEM in that it clearly differentiates deformed balloon surface, plaque particle, and retained contrast medium.

CONCLUSION

Plaque particles can be recovered from balloon surfaces after PTCA. Depending upon their size, they could lead to coronary spasm or microembolic phenomenon.

High salt- and SDS-stable DNA binding protein complexes with ATPase and protein kinase activity retained in chromatin-depleted nuclei

Cell lysis in presence of SDS and proteinase K followed by salting-out of residual polypeptides by dehydration and precipitation with saturated sodium chloride solution [Miller, S.A., Dykes, D.D. and Polesky, H.F., Nucleic Acids Res., 16, 1215, 1988] efficiently resolves deproteinized DNA. However, this DNA is still associated with prominent polypeptides which remain stably attached to DNA during further treatments, e.g. during repeated salting-out steps, prolonged incubation of DNA in 1% SDS or 4 M urea at 56 degrees C and ethanol precipitation. The persistent polypeptides (62, 52 and 40 kDa) released from Ehrlich ascites cell DNA were further characterized. Microsequencing indicates that the DNA binding polypeptides are not yet characterized at the sequence level. Nuclease digestion of the DNA releases stable DNA-protein complexes with the shape of globular particles (12.8 +/- 0.8 nm) and their larger aggregates in which DNA remains protected from nuclease digestion. The isolated DNA-polypeptide complexes show ATPase (Km = 7.4 x 10(-4) M) and protein kinase activity. Antibodies reveal a parallel distribution of the complexes with chromatin, however, the complexes are retained in chromatin-depleted nuclei.

Uptake and metabolism of 2,4,6-trinitrotoluene in higher plants

The fate of the explosive 2,4,6-TNT in plants is of major interest. Therefore, a method was developed to analyse TNT and derivatives in plant tissue. The method was utilized to investigate the uptake and metabolism of TNT inMedicago sativa andAllium schoenoprasum grown in hydroponic cultures containing TNT levels of 0.1 to 10 mg/1. Detectable concentrations of nitrotoluenes were significantly higher inAllium schoenoprasum than inMedicago sativa. The uptake of TNT in plants was directly related to the initial TNT level. The principal nitroaromatic components in roots and shoots of both plant species were identified as 4-ADNT and 2-ADNT in equal amounts, with substantially less TNT.

Third colloquium on cellular signal transduction: cell-cycle signalling. German Cancer Research Centre Heidelberg, 14 January 1994

The annual meeting of the DKFZ research programme Tumor Cell Regulation was originally conceived by its members as an internal forum for mutual information and progress discussion with their cooperating groups. However, because the attractive topics and contributions, these colloquia receive increasing attention also from non-members of the Tumor Cell Regulation programme and, this year, the number of the external participants exceeded even that of the internal members. We therefore anticipate this activity becoming a traditional event of wide interest.

Expression of mitochondrial genes and DNA-repair-related nuclear genes is altered in xeroderma pigmentosum fibroblasts

Differential hybridization was used to detect repair defects in xeroderma pigmentosum (XP) that are not amenable to current analyses. cDNA libraries were constructed from cytoplasmic RNA of normal and XP fibroblast strains (complementation groups A and D) and analyzed for differential gene expression. More than 40,000 lambda gt10 cDNA clones were differentially screened with in vitro transcripts made from cDNA in the pBluescript vector. Six differential clones were detected in the libraries of the XP group A and D strains which caused stronger or weaker signals when probed with transcripts from XP strains than with those from the normal strains. Two clones coded for mitochondrial genes: mitochondrial 16 S rRNA and ATPase 6L. Overexpression of mitochondrial genes in XP may indicate that functions of the ATP-generating system are impaired since such functions are intensified whenever they become insufficient, for example as a consequence of DNA damage. It is tempting to assume that abnormal mitochondria are one of the causes for the neurological malfunctions in XP. Furthermore, densitometric analysis of Northern blots revealed that mRNA of lactate dehydrogenase, chain M, was less abundant in four XP group A strains (extent of reduction: 70%) and in two XP group D strains (extent of reduction: 58%). Enzyme activity was also diminished. In addition, mRNA of the gene for glyceraldehyde-3-phosphate dehydrogenase was less expressed in the same XP group A and D fibroblast strains investigated (reduction in both complementation groups: 50%). Both glycolytic enzymes have nuclear functions apart from their role in sugar metabolism. Lactate dehydrogenase, chain M, is identical to a helix-destabilizing protein; it is closely associated with chromatin and unfolded DNA, suggesting a role in DNA synthesis and transcription. The 37-kDa subunit of glyceraldehyde-3-phosphate dehydrogenase is involved in transcription and was shown to be identical to uracil-DNA glycosylase, a base-excision repair enzyme. We presume that the nuclear functions of these glycolytic enzymes may be thwarted in the XP strains investigated and may account for malfunctions in XP, particularly for neurological disturbances.

Urate transport in brush-border membrane of human kidney

Mechanisms of urate transport were investigated in human renal brush-border membrane vesicles. The imposition of an outwardly directed Cl- gradient, in voltage-clamp and pH-clamp conditions, stimulated [14C]urate uptake. Organic anions, including pyrazinoate (PZA), probenecid, lactate, ketone bodies, succinate, and alpha-ketoglutarate in their monovalent forms, cis-inhibited [14C]urate uptake. The affinity order was PZA > urate > probenecid > other anions. Vesicle preloading with these anions trans-stimulated urate uptake. These observations demonstrate the presence of a urate/anion exchanger. p-Aminohippurate and OH- were not substrates for this exchanger. In the presence of an inwardly directed K+ gradient and valinomycin (intravesicular positive potential) [14C]urate uptake was stimulated. Voltage-sensitive [14C]urate uptake was cis-inhibited by organic anions in the following affinity order: urate > probenecid > PZA. The differences in affinity orders for the urate exchanger and the urate voltage-sensitive transport suggest different pathways for apical transport. The anion exchanger might be the main mechanism involved in urate tubular reabsorption in humans.

A human nuclear protein with sequence homology to a family of early S phase proteins is required for entry into S phase and for cell division

Molecular cloning and characterisation of a human nuclear protein designated BM28 is reported. On the amino acid level this 892 amino acid protein, migrating on SDS-gels as a 125 kDa polypeptide, shares areas of significant similarity with a recently defined family of early S phase proteins. The members of this family, the Saccharomyces cerevisiae Mcm2p, Mcm3p, Cdc46p/Mcm5p, the Schizosaccharomyces pombe Cdc21p and the mouse protein P1 are considered to be involved in the onset of DNA replication. The highest similarity was found with Mcm2p (42% identity over the whole length and higher than 75% over a conservative region of 215 amino acid residues), suggesting that BM28 could represent the human homologue of the S. cerevisiae MCM2. Using antibodies raised against the recombinant BM28 the corresponding antigen was found to be localised in the nuclei of various mammalian cells. Microinjection of anti-BM28 antibody into synchronised mouse NIH3T3 or human HeLa cells presents evidence for the involvement of the protein in cell cycle progression. When injected in G1 phase the anti-BM28 antibody inhibits the onset of subsequent DNA synthesis as tested by the incorporation of bromodeoxyuridine. Microinjection during the S phase had no effect on DNA synthesis, but inhibits cell division. The data suggest that the nuclear protein BM28 is required for two events of the cell cycle, for the onset of DNA replication and for cell division.

The human gene for nuclear protein BM28 (CDCL1), a new member of the early S-phase family of proteins, maps to chromosome band 3q21

BM28, a newly recognized human nuclear protein, possibly plays an important role in two crucial steps of the cell cycle e.g. the onset of DNA replication and cell division. It shows significant similarity to members of a recently defined family of early S-phase proteins. Using total plasmid DNA containing the complete coding sequence of the BM28 gene (CDCL1, for cdc-like 1) as a probe for fluorescence in situ hybridization, we have mapped the gene to chromosome band 3q21. This region is involved in specific structural chromosome aberrations found in acute myeloid leukemia (AML). Based on the function of BM28 and the chromosomal location of its gene, CDCL1 might prove to be a candidate for an oncogene affected by the chromosomal breaks and playing a pathogenetic role in AML.

Sequence of a complete murine cDNA reflecting an S phase-prevalent transcript encoding a protein with two types of nucleic acid binding motifs

Differential screening of a murine RNA-based lambda gt10 cDNA library with cell cycle phase-specific probes released a cDNA clone (lambda GS1) to a mRNA (1.8 kb) which is prevalent in the S phase of the cell cycle. The nucleotide sequence of the cDNA predicts a protein (RNPS1, 41 x 10(3) M(r) with two nucleic acid-binding domains separated by a proline-rich spacer. The N-terminal nucleic acid binding domain, about 80 amino acid residues in length, meets the requirements of an RNA recognition motif (RRM) including a perfect 'RNP-1 octamer'. The C-terminal nucleic acid binding domain spanning over 26 amino acid residues is prominent because it comprises three copies of the RRRS peptide. Domains of the latter type are considered to be involved in RNA and DNA-binding because comprised in many RNA and DNA-binding proteins.

Enhanced expression of mitochondrial genes in xeroderma pigmentosum fibroblast strains from various complementation groups

cDNA libraries constructed from cytoplasmic RNA of normal and xeroderma pigmentosum (XP) fibroblast strains were screened for differential gene expression. XP fibroblast strains included one representative of the complementation groups A, C, D, and one XP variant strain. The XP lambda gt10 cDNA libraries were differentially screened with in vitro transcripts made from cDNA in the pBluescript vector using both the same XP strain and the normal fibroblast strain. Eight differential clones were detected in the libraries of the XP group A, D, and C strains, which caused stronger signals when probed with transcripts from XP strains than with those from the normal strain. The cDNA clones were sequenced. Seven of the eight clones detected coded for three mitochondrial genes: subunit I of cytochrome c oxidase (complex IV of the respiratory chain), apocytochrome b (subunit of complex III), and 16-S rRNA. Two clones representing essentially (a) subunit I of cytochrome c oxidase and (b) 16-S rRNA diverged from the sequence of the human mitochondrial genome present in the data-base libraries. Clone a exhibited a transition mutation, clone b reflected a transcript of a mitochondrial genome rearranged in the 16-S rRNA gene, including four nucleotides of the adjacent tRNA(Leu) gene. The apparently enhanced expression of mitochondrial genes in XP cells, together with the changes in DNA sequence, seem to indicate that functions of the ATP-generating system were impaired. This defect may have originated from mutations due to lack of DNA repair. The data can be interpreted in the light of mitochondrial changes that cause human neuromyopathies to occur. In analogy to these diseases the neurological symptoms in XP might be explained by abnormal mitochondria.

Glutathione reductase in human and murine lung tumors: high levels of mRNA and enzymatic activity

The enzyme glutathione reductase (GR) (GSSG+NADPH+H+-->2 GSH+NADP+) plays a key role in the cellular defense against oxidative stress. High levels of GR activity are often associated with tumor growth and/or resistance mechanisms against drug and radiation therapy. In order to investigate the molecular basis of elevated glutathione reductase activities we studied the enzyme at the DNA, mRNA and protein levels in murine experimental tumor cell lines and in human lung tumors. A modified ultracentrifugation procedure was developed which allowed the simultaneous isolation of DNA and total cellular RNA. Out of 11 human bronchial carcinomas obtained from patients without prior chemotherapy, five tumors showed a GR activity which was 2.4 to 3.8 times higher than in the respective control tissues. In each case the elevated enzyme activity was accompanied by an elevated GRmRNA levels. For none of the tumors, GR gene rearrangement or amplification was observed by Southern blot analyses. The mouse tumor cell lines ASB XIV, Lewis lung carcinoma and EAT cells, also showed high levels of GRmRNA whereas this mRNA was hardly detectable in normal mouse lung tissue.

Folding of the four domains and dimerization are impaired by the Gly446-->Glu exchange in human glutathione reductase. Implications for the design of antiparasitic drugs

Glutathione reductase (NADPH+GSSG+H+-->NADP(+) + 2GSH) is a homodimeric flavoenzyme of known geometry. Each subunit contains four well-defined domains and contributes essential residues to the active sites; consequently, the monomer is expected to be inactive. As part of our program to develop dimerization inhibitors of human glutathione reductase (hGR) as antimalarial agents, we mutagenized the residues 446 and 447 which, together with their counterparts on the other subunit, represent the tightest contact between the subunits [Karplus, P. A., & Schulz, G. E. (1987) J. Mol. Biol. 195, 701-729]. Wild-type human glutathione reductase and mutants of this protein were produced in plasmid-transformed Escherichia coli SG5 cells. Active enzyme species, namely, wild-type hGR, N-terminally truncated delta(1-15)hGR, and the point mutant F447P-hGR, were purified by 2',5'-ADP-Sepharose chromatography and crystallization. Inactive mutants such as G446E-hGR or the double mutants G446E/F447P-hGR and G446P/F447P-hGR were isolated by immunoadsorption chromatography. G446E/F447P-hGR was studied in detail. This mutant behaved like a poorly folded monomeric protein, as indicated by the following properties: absence of the intersubunit disulfide bridge, Cys90-Cys90'; failure to bind FAD; failure to bind NADPH and analogues thereof; a short half-life (< 4 min) in E. coli cells; and high susceptibility to trypsin in vitro. The results suggest that the sequence around G446 can control dimerization as well as domain folding. This is unexpected since the FAD-binding domain and the NADPH-binding domain occur in many different enzymes and have been regarded as autonomous folding units.(ABSTRACT TRUNCATED AT 250 WORDS)

Phosphorylation of Soybean (Glycine max L.) Nodule Phosphoenolpyruvate Carboxylase in Vitro Decreases Sensitivity to Inhibition by L-Malate

Phosphoenolpyruvate carboxylase (PEPC) from soybean (Glycine max L.Merr.) nodules was purified 187-fold to a final specific activity of 56 units mg-1 of protein. Sodium dodecyl sulfate (SDS) polyacrylamide gel electrophoresis (PAGE) revealed one major polypeptide band, with a molecular mass of 110 kD, after the final purification step. Two-dimensional PAGE resolved four isoelectric forms of the purified enzyme. Antibodies raised against the purified enzyme immunoprecipitated PEPC activity from a desalted nodule extract. Two cross-reacting bands were obtained when protein immunoblots of crude nodule extracts subjected to SDS-PAGE were probed with the antiserum. One of these corresponded to the 110-kD subunit of PEPC, and the other had a molecular mass of about 60 kD. PEPC was shown to be activated in a time-dependent manner when desalted soybean nodule extracts were preincubated with Mg.ATP in vitro. Activation was observed when PEPC was assayed at pH 7 in the absence of glycerol but not at pH 8 in the presence of glycerol. When o.5 mM L-malate was included in the assay, activation was much more pronounced than without malate. Maximal activation was 30% in the absence of L-malate and 200% in its presence. The L-malate concentrations producing 50% inhibition of PEPC activity were o.35 and 1.24 mM, respectively, before and after preincubation with Mg.ATP. The antiserum against soybean nodule PEPC was used to immunoprecipitate PEPC from a desalted nodule extract that had been preincubated with Mg.[[gamma]-32P]ATP. The immunoprecipitate was then subjected to SDS-PAGE, followed by autoradiography. The autoradiograph revealed intense labeling of the 110-kD subunit of PEPC following preincubation with [[gamma]-32P]ATP. The data suggest that soybean nodule PEPC becomes phosphorylated by an endogenous protein kinase, resulting in decreased sensitivity of the enzyme to inhibition by L-malate in vitro. The results are discussed in relation to the proposed functions of PEPC in legume nodules.

cDNA-derived molecular characteristics and antibodies to a new centrosome-associated and G2/M phase-prevalent protein

Differential screening of a murine RNA-based cDNA library with cell cycle phase-specific transcripts released a cDNA clone (lambda CCD41) to a mRNA (1.349 kb) which, according to the mode of its detection, increases as expected during the cell cycle. The molecular characteristics of the protein (27 × 10(3) M(r)) encoded by this mRNA were deduced from the cDNA sequence and antibodies were prepared against the recombinant protein. Immunofluorescence studies performed with PtK2 cells revealed that the amount of the antigen specified by the CCD41 sequence increases during the cell cycle out of proportion with the DNA content. In G1 phase cells, the antigen is exclusively located at the site of the centrosome. During cell cycle progression the antigen becomes also detectable in perinuclear vesicles that increase in number and size, reaching a maximum in G2 phase cells. The centrosomal location of the CCD41 antigen was investigated in relation to another centrosomal antigen, centrosomin A. Since the latter antigen is detected by a monoclonal antibody reacting specifically and permanently with the centrosomes in PtK2 cells throughout the cell cycle it was possible to investigate the relative positions of the two proteins at the site of the centrosome and to add new information about the general architecture of the organelle and its changes during the cell cycle. While the centrosomin A antibody detects the pronounced cell cycle stage-dependent shape changes of the centrosome, the CCD41-encoded protein appears to be localized as a compact structure inside the centrosome. Its epitopes are exposed throughout the cell cycle except during a brief period immediately after the formation of the daughter centrosome.

Identification of human satellite DNA sequences associated with chemically resistant nonhistone polypeptide adducts

A fraction of DNA fragments of highly purified and completely unfolded eukaryotic DNA inevitably remains associated with chemically resistant nonhistone DNA-polypeptide complexes. This fraction can be isolated by nitrocellulose filtration because the polypeptide-associated DNA fragments are retained on nitrocellulose filters while bulk DNA passes through the filters. The fraction of AluI-fragmented DNA from human placenta retained on filters as a result of the binding factors (R-DNA, approximately 12%) represents a subset of genomic sequences with a sequence complexity different from unfractionated DNA and DNA recovered in the filtrate (F-DNA). DNA sequences prevalent in the retained fraction were detected by differential plaque hybridization of a recombinant lambda gt10 library with radiolabeled F- and R-DNA fractions. Several recombinant phages showing much stronger hybridization signals with the R-DNA probe than with the F-DNA probe were selected, plaque-purified and analyzed. Analysis of the inserts of such clones showed that repetitive DNA sequences of the alphoid dimeric and tetrameric family, satellite III and satellite III-like sequences are highly enriched in the retained fraction, which indicates that these sequences specifically attract the polypeptides involved in the tightly bound and resistant complexes. This property of repetitive sequences is of interest since tandemly repetitive sequences have been suggested to code for locus-specific fixation and stabilization of the chromatin fiber in the cell nucleus.

Generating compatible translation initiation regions for heterologous gene expression in Escherichia coli by exhaustive periShine-Dalgarno mutagenesis. Human glutathione reductase cDNA as a model

Adaptation of eucaryotic cDNA to heterologous expression was studied by mutating the translation initiation (TI) region upstream (mTI) and downstream (MTI) of the start codon. In the mTI subregion the 8 bases flanking the invariant Shine-Dalgarno motif GG-AG were mutagenized exhaustively, while the MTI subregion was subjected to random silent mutations at the wobble positions. The quality of a given TI sequence was judged on the basis of expressed enzyme activity. Low-yield and high-yield mutants of both TI subregions were selected and recombined systematically. The analysis of these double cartridges gave the following results: 1. As a rule, an unfavourable MTI subregion can be compensated for by mutations in the mTI subregion and vice versa. 2. The compatibility between mTI and MTI subregion is explainable at least in part by a low interaction tendency; a delta G(o)'-value of -10.7 kcal/mol appears to be a physical threshold for heterologous cDNA expression. 3. On the basis of periShine-Dalgarno mutations, the expression yield for different cDNA sequences could be increased by 1 to 2 orders of magnitude. One of these sequences encoded delta(1-15)human glutathione reductase, a mutant lacking the flexible N-terminal extension of the protein. In conclusion, to study and overcome TI region-based expression problems it is worthwhile to start out with a versatile vector containing exhaustive mutations in the periShine-Dalgarno sequences; as a rule the coding MTI subregion can be kept unchanged.

Isoliquiritigenin, a strong nod gene- and glyceollin resistance-inducing flavonoid from soybean root exudate

Isoflavonoid signal molecules from soybean (Glycine max (L.) Merr.) seed and root exudate induce the transcription of nodulation (nod) genes in Bradyrhizobium japonicum. In this study, a new compound with symbiotic activity was isolated from soybean root exudate. The isolated 2',4',4-trihydroxychalcone (isoliquiritigenin) is characterized by its strong inducing activity for the nod genes of B. japonicum. These genes are already induced at concentrations 1 order of magnitude below those required of the previously described isoflavonoid inducers genistein and daidzein. Isoliquiritigenin is also a potent inducer of glyceollin resistance in B. japonicum, which renders this bacterium insensitive to potentially bactericidal concentrations of glyceollin, the phytoalexin of G. max. No chemotactic effect of isoliquiritigenin was observed. The highly efficient induction of nod genes and glyceollin resistance by isoliquiritigenin suggests the ecological significance of this compound, although it is not a major flavonoid constituent of the soybean root exudate in quantitative terms.

Detection of the 125-kDa nuclear protein mitotin in centrosomes, the poles of the mitotic spindle, and the midbody

Mitotin is a nuclear protein detectable in all proliferating cells investigated so far, including human and plant cells. In interphase cells the protein is localized mainly in the nucleoplasm. In G2/M phase it displays a characteristic redistribution and a marked increase which initiated the name mitotin. This study presents the precise localization of mitotin in cytoplasmic structures in two cell types, the potoroo rat kangaroo PtK2 cell and the human lung cancer EPLC 65 cell. In addition to its nuclear localization the antigen is detectable in centrosomes, in the poles of the mitotic spindle, and along spindle fibers. During the last mitotic stages, cytokinesis and reconstitution of nuclei, mitotin displays a rapid decrease and another redistribution. A significant amount of the antigen is retained in the bridge connecting the dividing cells, the midbody.