A possibility to achieve genetic transformation in the platyfish-swordtail system (Platypoecilus maculatus — Xiphophorus helleri)

Summary In order to determine how informative homologous donor DNA might be made available to propigment cells of the recipientXiphophorus helleri for transformation, labelled heterologous DNA fromE. coli was injected into the neural crest region or the yolk sac of embryos of the recipient. On the basis of the degradation rate of the donor DNA and the incorporation rate of radioactivity into the recipient DNA, it is concluded that injection into the neural crest region may be a suitable method to make available informative homologous donor DNA for transformation.Supported by DFG through SFB No. 103, and by Stiftung Volkswagenwerk.     

Zur Wirkung von Zn++ auf die Nukleinsäurebiosynthese von Aszites-Tumorzellen

Summary Ascites tumour cells have been employed to study the reactivity of Zn⁺⁺ on nucleic acid biosynthesis. 10^–4 M Zn⁺⁺ caused a selective inhibition of DNA synthesis of intact cells. The rate of RNA- and protein-biosynthesis, however, remained unchanged. The activity of DNA polymerase as well as DNA dependent RNA polymerase was strongly affected by Zn⁺⁺ in vitro.     

Host cell reactivation of ozone-treated T3 bacteriophage by different strains ofEscherichia coli

Summary Host cell reactivation capacity for ozone T3 phage was determined for differentE. coli strains deficient in one or more of the DNA repair mechanisms. The results indicate that DNA polymerase I appears to play a key role in the repair of damage produced on the DNA by ozone while thelexA gene product seems to play a minor one.This research was sponsored by the National Sciences and Engineering Council of Canada. One of us (PLH) acknowledges a scholarship from the NSERCof Canada.     

Homologies ofNeurospora homothallic species using repeated and nonrepeated DNA sequences

Summary DNA:DNA hybridization studies of the homothallic species ofNeurospora showed that the repeated DNA sequences provided no means of distinction among them. Hybridization with nonrepeated DNA sequences, however, showed that theN. terricola species was quite unlike the others. These studies suggest that heterothallism might have evolved from homothallism inNeurospora.Supported in part by a contract with the US Department of Energy. We are grateful to Dr Lafayette Frederick of this Department for helping us with the cultures ofN. terricola andN. galapagosensis.     

Satellite DNA from the beetleTenebrio molitor

Summary A 142 base-pair satellite DNA from the mealworm beetle,Tenebrio molitor, has been cloned and sequenced. The satellite DNA is revealed by making a restriction digest of genomic DNA with either EcoRI or Hinfl, and constitutes approximately 49% of the genomic DNA. The presence of huge amounts of satellite DNA correlates well with the prominent blocks of heterochromatin found in tenebrionid beetles. A similar restriction digest ofXanthogaleruca luteola genomic DNA does not release a prominent satellite component.     

Alkyltransferase-like proteins: molecular switches between DNA repair pathways

Alkyltransferase-like proteins (ATLs) play a role in the protection of cells from the biological effects of DNA alkylation damage. Although ATLs share functional motifs with the DNA repair protein and cancer chemotherapy target O ⁶-alkylguanine-DNA alkyltransferase, they lack the reactive cysteine residue required for alkyltransferase activity, so its mechanism for cell protection was previously unknown. Here we review recent advances in unraveling the enigmatic cellular protection provided by ATLs against the deleterious effects of DNA alkylation damage. We discuss exciting new evidence that ATLs aid in the repair of DNA O ⁶-alkylguanine lesions through a novel repair cross-talk between DNA-alkylation base damage responses and the DNA nucleotide excision repair pathway.     

Cytochemischer Nachweis phasen- und regionsspezifischer Veränderungen des DNS-Gehaltes während der Embryogenese vonTriturus vulgaris

Summary The DNA content of isolated cells ofTriturus vulgaris embryos (morula through early tail-bud) was measured cytophotometrically. In various regions (entoderm, chordamesoderm, neuroectoderm, presumptive epidermis) considerable differences occur. In particular, some phase-specific DNA increases (approximately 11%) of short duration were detected, which are correlated with the onset of cyto- and organodifferentiation, respectively, and which are caused independent of the interphase DNA reduplication.     

PCR jumping in clones of 30-million-year-old DNA fragments from amber preserved termites (Mastotermes electrodominicus)

DNA from 30-million-year-old amber preserved termites (Mastotermes electrodominicus) was PCR amplified with nuclear ribosomal RNA small subunit primers and cloned into the TA vector (INVITROGEN). We obtained several classes of recombinant clones as a result. AuthenticMastotermes electrodominicus clones were identified. The source of other classes of clones was identified as contaminants of the ancient DNA template. Several of the clones appeared to be chimeric in structure with half of the clone identical to the termite sequence and the other half identical to contaminant sequences. The phenomenon of PCR jumping was identified as a possible source for the chimeric clones.     

Sequence organization in the DNA of three Selachians

Summary The DNA interspersion pattern in 3 Selachians (R. asterias, T. marmorata andS. stellaris) has been studied through the reassociation kinetics of short (0.3 Kb) and long (2.5 Kb) DNA fragments. Preliminary results show that most of the DNA (approximately 80%) of these organisms is arranged according to a short-period interspersion pattern. A notable resemblance to the pattern previously described in the teleosteanSalmo trutta has been observed.     

Application de méthodes d'analyse biochimique à une étude taxonomique: les corégones du lac de Neuchâtel

Summary Two closely related forms ofCoregonus from Lake Neuchatel were examined cytologically and biochemically, in order to ascertain the chromosome number and the DNA content of haploid and diploid nuclei.Coregonus fera has 2N=78 ± 2 chromosomes, and a DNA content (diploid) of 5.8 × 10⁻⁹ mg;Coregonus macrophthalmus, 2N=78⁺ ± 3, DNA content of 6.1 × 10⁻⁹ mg. The difference between the two DNA constants is statistically significant. These results do not support the hypothesis which postulates that polyploidy may be a determining factor in the speciation of these fishes.      

Emerging connections between DNA methylation and histone acetylation

Modifications of both DNA and chromatin can affect gene expression and lead to gene silencing. Evidence of links between DNA methylation and histone hypoacetylation is accumulating. Several proteins that specifically bind to methylated DNA are associated with complexes that include histone deacetylases (HDACs). In addition, DNA methyltransferases of mammals appear to interact with HDACs. Experiments with animal cells have shown that HDACs are responsible for part of the repressive effect of DNA methylation. Evidence was found in Neurospora that protein acetylation can in some cases affect DNA methylation. The available data suggest that the roles of DNA methylation and histone hypoacetylation, and their relationship with each other, can vary, even within an organism. Some open questions in this emerging field that should be answered in the near future are discussed.     

The karyotype and genome structure of the pirate perchAphredoderus sayanus (Aphredoderidae: Teleostei)

Summary The standard karyotype, genome size (DNA content), and genomic DNA base composition and distribution of the relict paracanthopterygian fish,Aphredoderus sayanus, were investigated. Several features of theA. sayanus genome appear to be derived rather than primitive conditions. These include a large number (at least 10 pairs) of bi-armed chromosomes, a low genome size, and high DNA asymmetry. This may indicate thatA. sayanus is not a typical paracanthopterygian fish in terms of its genome structure.     

Genome size in the green toad (Bufo viridis) group

Summary Specimens of the green toad,Bufo viridis, from Morocco to Kirgizistan, have identical DNA amounts per erythrocyte nucleus. 1 specimen from Kirgizistan is a tetraploid. Of 3 closely related species,B. calamita andB. brongersmai have about the same DNA amount asB. viridis, whileB. latastii from Afghanistan has 36% more DNA per nucleus.     

Teneur des gamètes mâles et femelles d'Allomyces en acides nucléiques et composition comparée d'une fraction saline de l'acide ribonucléique des gamétanges

Summary Estimation of RNA and DNA by gamete in the unisexual strains ofAllomyces showed the amount of RNA to be twice as much in the female as in the male. The amount of DNA was only slightly, though consistently, higher in the female. Comparison of NaCl-soluble RNA from young gametangia of the unisexual strains showed no appreciable difference in the nucleotide composition, although a tendency for a higher purine pyrimidine ratio was noticed in the males.     

Changes in the thermal denaturation profiles of DNA from different developmental stages of the newtTriturus vulgaris

Summary The melting profiles of DNA samples from the early gastrula and early neurula ofTriturus vulgaris are essentially the same, whereas DNA from mid to late gastrula possesses higher T_m values and shows a deviation from the regular sigmoidal shape at temperatures above T_m. The plot on normal probability paper indicates a second DNA fraction which melts at higher temperatures and, consequently, it has a higher GC-content than the bulk DNA. These facts confirm our idea that differential DNA replication occurs during gastrulation.     

Preferential destruction of chloroplast nucleoids in zygotes in green algaeDictyosphaeria cavernosa andAcetabularia calyculus

Summary The preferential destruction of chloroplast nucleoids in young zygotes in the coenocytic algaDictyosphaeria cavernosa and the giant unicellular algaAcetabularia calyculus was studied by high resolution epifluorescent microscopy. The chloroplast nucleoids (DNA) in the chloroplast from one of the parents were preferentially destroyed soon after the mating of male and female gametes.     

1Alpha,25-dihydroxyvitamin D3 inhibits hepatic chromosomal aberrations, DNA strand breaks and specific DNA adducts during rat hepatocarcinogenesis

The possible promoting effect of streptozotocin (STZ; 65 mg/kg body weight, intraperitoneal)-induced diabetes during 2-acetylaminofluorene (2-AAF; 0.04% in basal diet)-initiated hepatocarcinogenesis and modulatory effect of 1α,25-dihydroxyvitamin D₃ (VD₃; 0.3 μg/0.1 ml in propylene glycol, per os) were investigated by monitoring chromosomal aberrations (CAs), DNA strand breaks and specific DNA adducts in rat liver. VD₃ treatment (twice a week) was started 4 weeks before the 2-AAF regimen and continued throughout the study. Aberrant metaphase chromosomes were counted from the regenerating hepatocytes 15, 30 or 45 weeks after STZ injection, while DNA strand break and adduct assays were performed 45 days post-STZ treatment. Dietary exposure to 2-AAF elicited a substantial increase in CAs and elevated the extent of DNA strand breaks and formation of N-(deoxyguanosin-8-yl)-2-aminofluorene. A promoting effect of STZ was evident from CAs coupled with DNA strand break analysis. VD₃ treatment substantially reducted 2-AAF+STZ-induced CAs as well as DNA strand breaks and adducts. Thus, VD₃ appears to be effective in suppressing liver-specific early chromosomal as well as DNA damage during the process of rat hepatocarcinogenesis initiated with 2-AAF and promoted by STZ contributing to its promise as a cancer chemotherapeutic agent. Received 27 April 2001; accepted 22 May 2001     

Kelletinin I and kelletinin A from the marine molluscBuccinulum corneum are inhibitors of eukaryotic DNA polymeraseα

Summary The inhibitory effect of esters of p-hydroxybenzoic acid (kelletinins I and A), extracted from the marine gastropodBuccinulum corneum, have been tested on eukaryotic and prokaryotic enzymes of DNA metabolism such as DNA polymerases and , DNA polymerase I, Exo III, pancreatic DNAse I, micrococcal DNAse andE. coli RNA polymerase. Kelletinin I and kelletinin A inhibit preferentially DNA polymerase. The inhibitory effect of kelletinin I involves the hydroxyl group of p-hydroxybenzoic acid.     

EGF-induced programmed cell death of human mammary carcinoma MDA-MB-468 cells is preceded by activation of AP-1

MDA-MB-468 is a human mammary adenocarcinoma cell line that overexpresses the epidermal growth factor (EGF) receptor and undergoes programmed cell death (apoptosis) in response to EGF treatment. Programmed cell death was shown to be greatly enhanced when cells were growth-arrested prior to EGF treatment. Apoptosis was characterized by an initial rounding up and detachment of the cells from their substrate starting about 12 h after EGF treatment, followed by chromatin condensation, nuclear fragmentation and oligonucleosomal fragmentation of the DNA at about 24 to 48 h. Cell death was dependent on de novo protein synthesis. We found a rapid induction of c-fos, c-jun and junB at the mRNA level after about 30 min of EGF treatment and a more delayed upregulation of fosB and fra-1. The junD gene was expressed in the absence of EGF, and it was moderately induced within 30 min of growth factor addition. The increase of the different fos and jun mRNAs were paralleled by an increase of activator protein-1 (AP-1) DNA binding activity. A characterization of the AP-1 complex revealed similar levels of several Fos and Jun proteins. Based on the kinetics of AP-1 accumulation and cell death, it seems likely that AP-1 contributes to the apoptotic cell death of EGF receptor-overexpressing MDA-MB-468 cells. Received 21 July 1997; received after revision 6 November 1997; accepted 6 November 1997     

A rhodopsin-like protein in Cyanophora paradoxa: gene sequence and protein immunolocalization

Here, we report the DNA sequence of the rhodopsin gene in the alga Cyanophora paradoxa (Glaucophyta). The primers were designed according to the conserved regions of prokaryotic and eukaryotic rhodopsin-like proteins deposited in the GenBank. The sequence consists of 1,272 bp comprised of 5 introns. The correspondent protein, named Cyanophopsin, showed high identity to rhodopsin-like proteins of Archea, Bacteria, Fungi, and Algae. At the N-terminal, the protein is characterized by a region with no transmembrane α-helices (80 aa), followed by a region with 7α-helices (219 aa) and a shorter 35-aa C-terminal region. The DNA sequence of the N-terminal region was expressed in E. coli and the recombinant purified peptide was used as antigen in hens to obtain polyclonal antibodies. Indirect immunofluorescence in C. paradoxa cells showed a marked labeling of the muroplast (aka cyanelle) membrane.