PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Extrachromosomal Inheritance”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 901 records · Page 50Linked to original sources
PubMed1995

Giant linear plasmids of beta-lactam antibiotic producing Streptomyces.

A survey of the total cellular DNA from five beta-lactam antibiotic-producing Streptomyces spp. by pulsed field gel electrophoresis was conducted to investigate the presence of linear plasmids. Streptomyces clavuligerus NRRL 3585 contained two giant linear plasmids of 120 and 430 kb, in addition to the well-characterized 11.7 kb linear plasmid. Streptomyces griseus NRRL 3851 contained a single giant linear plasmid of 120 kb, and Streptomyces jumonjinensis NRRL 5741 contained two giant linear plasmids (220 and 280 kb), and two smaller linear plasmids. No plasmids were identified in Streptomyces cattleya NRRL 3841 or Streptomyces lipmannii NRRL 3584. Southern hybridization did not reveal any homology shared by these plasmids, and beta-lactam antibiotic synthesis gene clusters were located on the chromosome.

Anti-Bacterial Agents↗
PubMed1980

3 micron DNA - an extrachromosomal ribosomal DNA in the yeast Saccharomyces cerevisiae.

A new class of extrachromosomal DNA which consists predominantly of covalently closed molecules with lengths around 3 micron, has been detected in Saccharomyces cerevisiae strain 6-1G-P188 from the Peterhof collection. Restriction analysis of the 3 micron DNA as well as of recombinant plasmids carrying HindIII fragments of the 3 micron DNA permitted construction of a physical map of the new extrachromosomal DNA species, and detection of two types differing by one EcoRI restriction site. Molecular hybridization, as well as comparison of the restriction maps, revealed the complete structural identity of the 3 micron DNA with a chromosomal repetitive unit of rDNA containing the genes for 25 S, 18 S, 5.8 S and 5 S rRNAs.

Chromosome Mapping↗
PubMed1980

Cloning and expression of Trypanosoma brucei kinetoplast DNA in Escherichia coli.

The kinetoplast DNA of Trypanosoma brucei is made of two components: mini-circles (1 kb, 90% of total kDNA) and maxi-circles (20 kb, 10%) of total kDNA). These are interlocked to form a network of about 10 000 kb. In order to analyse the components of such a network structure, we have cloned individual mini-circle molecules and two of the three EcoRI maxi-circle fragments in E. coli. Cloned mini-circles are somewhat heterogeneous in size and their restriction patterns are completely different. Despite this heterogeneity all are found to contain a homologous region(s) defined by DNA/DNA hybridization. The maxi-circles probably correspond to the mitochondrial DNA of other organisms and, in contrast to mini-circles, do not show sequence heterogeneity. One of the two cloned maxi-circle EcoRI fragments is able to direct the synthesis of two polypeptides of 10 300 and 13 500 daltons in E. coli mini-cells. Detailed analysis of this phenomenon shows that both structural genes and promoter(s) are located within the cloned maxi-circle fragment.

Animals↗
PubMed1981

Extrachromosomal rDNA of Tetrahymena thermophila is not a perfect palindrome.

We have determined the restriction-endonuclease-cleavage map and the nucleotide sequence of the central 1.4 kb fragment of the macronuclear extrachromosomal rDNA of Tetrahymena thermophila. These data demonstrate that this molecule is not a perfect palindrome, having a 29 bp AT-rich non-palindromic sequence at its center. This observation is important in determining the mechanism by which a single chromosomally integrated rRNA gene in the micronucleus is rearranged and amplified during sexual development to yield multiple copies of extrachromosomal rDNA in the macronucleus.

Animals↗
PubMed1985

Two mammalian cell systems for propagation of the hepatitis B virus genome in extrachromosomal and chromosomally integrated states: production of the surface and e antigens.

A recombinant plasmid consisting of (i) the entire genome of hepatitis B virus (HBV) DNA, (ii) the replication origin of SV40 virus, and (iii) a deletion derivative of pBR322 was introduced either into COS cells of monkey origin which constitutively express SV40 large T antigen, or into thymidine kinase(TK)-deficient mouse L cells together with the TK DNA of Herpes simplex virus. In the COS cell system, the transfecting recombinant DNA replicates via SV40 origin and is maintained in an autonomously replicating state. The cells carrying these extrachromosomal elements express the hepatitis B surface antigen gene at moderate rate, and release the products into the culture medium. However, neither core antigen nor e antigen expression was detected in this system. In the L cell system, the transformed L cells carry the recombinant DNA in a chromosomally integrated state. Such cells express the surface antigen gene at high rate, and release the products into the culture medium. This system also excretes the e antigen into the culture medium. The core antigen was not detected.

Animals↗
PubMed1994

Structure and organization of a stable extrachromosomal element in human cells.

We have determined the structure and organization of a 630-kb extrachromosomal element (amplisome) containing the dihydrofolate reductase-encoding gene (DHFR) in a methotrexate (MTX)-resistant human cell line, HeLa-Bu25-10B3. The size and copy number of amplisomes have previously been found to remain remarkably stable with or without selection. Both linear and open circular 630-kb amplisomes are present in these cells. We have been able to isolate the linear amplisomes after pulsed-field gel electrophoresis (PFGE), and transfect the amplisomes into MTX-sensitive recipient cells by electroporation, thus demonstrating that DNA as large as 630 kb can be transfected into mammalian cells. The NotI restriction site immediately upstream from DHFR on the circular amplisome is devoid of methylation, suggesting that it is transcriptionally active. Restriction mapping by PFGE reveals that there is only one copy of DHFR per amplisome and no repetitive structure is observed. The small size of the amplisomes, their stability and our ability to transfect large DNA molecules provide the necessary ingredients for the development of mammalian cloning vectors for large DNA fragments.

Azacitidine↗
PubMed1994

Structural analysis of the chloroplastic and cytoplasmic aldolase-encoding genes implicated the occurrence of multiple loci in rice.

The genes AldP and AldC-a, encoding the rice chloroplastic (cp) and cytoplasmic (ct) types of aldolase, respectively, were isolated and sequenced, and their transcription start points (tsp) were determined. Organization of the two genes was found to differ greatly; AldP consisted of six exons while AldC-a consisted of two exons. The deduced amino acid (aa) sequence of AldP contained a cp stromal targeting signal, followed by a sequence that matches the experimentally determined N-terminal sequence of mature AldP. The two enzymes share only 55% aa identity. However, rice AldP had about 73% homology with the cp aldolase of spinach. Also, the homology of AldC-a with maize, spinach and Arabidopsis thaliana cytoplasmic aldolases ranged from 70 to 90%. Southern blot analyses indicated that AldP is encoded at a single locus, whereas the gene encoding the ct counterpart is distributed at three loci on the genome. This feature is quite different from those of maize and spinach, in which only one locus was found for the ct aldolase.

Amino Acid Sequence↗
PubMed1996

Leigh syndrome associated with mitochondrial DNA 8993 T-->G mutation and ragged-red fibers.

We report a 6-month-old girl with episodic hyperventilation, myoclonus, disturbed consciousness, and lactic acidosis. Brain sonogram revealed progressive ventriculomegaly, and MRI showed symmetric low densities over the putamen bilaterally with diffuse cortical cystic lesions. Ragged-red fibers were noted in the muscle biopsy. Molecular analysis revealed a heteroplasmic T-->G mutation at nucleotide position (np) 8993 of mitochondrial DNA (mtDNA). The proportion of the mutant mtDNA in the muscle of the proband was estimated to be 86%. Her mother and maternal uncle also harbored the same mutant mtDNA (54 and 48% in their leukocytes, respectively). One of her sisters carried 64% mutant mtDNA in her leukocytes, but another sister did not. These results suggest that this mutant mtDNA is transmitted through the maternal lineage in this family in a randomly segregated manner. To our knowledge, this is the first report of a Chinese patient with Leigh syndrome associated with the T-->G substitution at np 8993 of mtDNA.

DNA, Mitochondrial↗
PubMed1991

A new multisequence family in human.

By hybridizing total human DNA with probes derived from the extrachromosomal circular DNA fraction of cultured cells, we detected a human multisequence family, called chAB4, previously unknown. Approximately 50 copies of this sequence are located in the haploid human genome. The repetition units of chAB4 are 35 kb long and the units are tandemly arranged. DNA sequence analysis of parts of the chAB4 unit revealed no direct evidence for a possible function of the family, but possibly chAB4 harbors a gene. Family members are located on human chromosomes 1, 3, and 9 and on the short arms of chromosomes 13-15, 21, and 22. Therefore, in addition to the rDNA, chAB4 is the second class of clustered repetitive sequences with a relatively long repetition unit localized on the short arms of all acrocentric chromosomes. Some evolutionary aspects arising from the structure of chAB4, the established parts of its DNA sequences, and the chromosomal localization of this new multisequence family are discussed.

Autoradiography↗
PubMed2005

"Protoplasm...is soft wax in our hands": Paul Kammerer and the art of biological transformation.

Paul Kammerer's career ended in scandal in 1926 over tampering with his evidence for "Lamarckian" evolution--the infamous midwife toad. But although Kammerer's conclusions proved false, his evidence was probably genuine. In any case his arguments were not simply for Lamarckism and against Darwinism, as the theories are understood today. If we look beyond the scandal, the Kammerer story shows us a great deal about early 20th-century biology: the range of new ideas about heredity and variation, competing theories of biological and cultural evolution and their applications in eugenics, new kinds of laboratories and professional roles for biologists, and changing standards for documenting experimental results.

Adaptation, Physiological↗
PubMed2004

The mitochondrial plasmid pAL2-1 reduces calorie restriction mediated life span extension in the filamentous fungus Podospora anserina.

Calorie restriction is the only life span extending regimen known that applies to all aging organisms. Although most fungi do not appear to senesce, all natural isolates of the modular filamentous fungus Podospora anserina have a limited life span. In this paper, we show that calorie restriction extends life span also in Podospora anserina. The response to glucose limitation varies significantly among 23 natural isolates from a local population in The Netherlands, ranging from no effect up to a 5-fold life span extension. The isolate dependent effect is largely due to the presence or absence of pAL2-1 homologous plasmids. These mitochondrial plasmids are associated with reduced life span under calorie restricted conditions, suggesting a causal link. This has been substantiated using three combinations of isogenic isolates with and without plasmids. A model is proposed to explain how pAL2-1 homologues influence the response to calorie restriction.

Caloric Restriction↗
PubMed2006

Prion proteins as genetic material in fungi.

Prions are infectious proteins. Several prions have been identified in fungi where they behave as non-Mendelian cytoplasmic genetic elements. Most of these prions propagate as self-perpetuating amyloid aggregates thus providing an example of structural heredity. In yeast, prion propagation requires the Hsp104 disaggregase presumably to sheer amyloid assemblies and generate more fiber ends. Recent work in yeast shows that amyloid structure polymorphism underlies the prion strain phenomenon and influences species barriers. Structural models for the amyloid form of several fungal prion proteins are now available. All propose a cross beta-organization with parallel beta-sheets. Whether or not some of the fungal prions might be beneficial to their host is still a debated issue.

Amino Acid Sequence↗
PubMed2005

Catarrhine primate divergence dates estimated from complete mitochondrial genomes: concordance with fossil and nuclear DNA evidence.

Accurate divergence date estimates improve scenarios of primate evolutionary history and aid in interpretation of the natural history of disease-causing agents. While molecule-based estimates of divergence dates of taxa within the superfamily Hominoidea (apes and humans) are common in the literature, few such estimates are available for the Cercopithecoidea (Old World monkeys), the sister taxon of the hominoids in the primate infraorder Catarrhini. To help fill this gap, we have sequenced the entire mitochondrial DNA (mtDNA) genomes from a representative of three cercopithecoid tribes, Cercopithecini (Chlorocebus aethiops), Colobini (Colobus guereza), and Presbytini (Trachypithecus obscurus), and analyzed these new data together with other catarrhine mtDNA genomes available in public databases. Molecular divergence date estimates are dependent on calibration points gleaned from the paleontological record. We defined criteria for the selection of good calibration points and identified three points meeting these criteria: Homo-Pan, 6.0 Ma; Pongo-hominines, 14.0 Ma; hominoid/cercopithecoid, 23.0 Ma. Because a uniform molecular clock does not fit the catarrhine mtDNA data, we estimated divergence dates using a penalized likelihood and a Bayesian method, both of which take into account the effects of rate differences on lineages, phylogenetic tree structure, and multiple calibration points. The penalized likelihood method applied to the coding regions of the mtDNA genome yielded the following divergence date estimates, with approximate 95% confidence intervals: cercopithecine-colobine, 16.2 (14.4-17.9) Ma; colobin-presbytin, 10.9 (9.6-12.3) Ma; cercopithecin-papionin, 11.6 (10.3-12.9) Ma; and Macaca-Papio, 9.8 (8.6-10.9) Ma. Within the hominoids, the following dates were inferred: hylobatid-hominid, 16.8 (15.0-18.5) Ma; Gorilla-Homo+Pan, 8.1 (7.1-9.0) Ma; Pongo pygmaeus pygmaeus-P. p. abelii, 4.1 (3.5-4.7) Ma; and Pan troglodytes-P. paniscus, 2.4 (2.0-2.7) Ma. These dates were similar to those found using penalized likelihood on other subsets of the data, but slightly younger than several of the Bayesian estimates.

Africa↗
PubMed2005

Fisherian and Wrightian perspectives in evolutionary genetics and model-mediated imposition of theoretical assumptions.

I investigate how theoretical assumptions, pertinent to different perspectives and operative during the modeling process, are central in determining how nature is actually taken to be. I explore two different models by Michael Turelli and Steve Frank of the evolution of parasite-mediated cytoplasmic incompatility, guided, respectively, by Fisherian and Wrightian perspectives. Since the two models can be shown to be commensurable both with respect to mathematics and data, I argue that the differences between them in the (1) mathematical presentation of the models, (2) explanations, and (3) objectified ontologies stem neither from differences in mathematical method nor the employed data, but from differences in the theoretical assumptions, especially regarding ontology, already present in the respective perspectives. I use my "set up, mathematically manipulate, explain, and objectify" (SMEO) account of the modeling process to track the model-mediated imposition of theoretical assumptions. I conclude with a discussion of the general implications of my analysis of these models for the controversy between Fisherian and Wrightian perspectives.

Adaptation, Physiological↗
PubMed2006

The role of DNA polymerase iota in UV mutational spectra.

UVB (280-320 nm) and UVC (200-280 nm) irradiation generate predominantly cyclobutane pyrimidine dimers (CPDs) and (6-4) photoproducts in DNA. CPDs are thought to be responsible for most of the UV-induced mutations. Thymine-thymine CPDs, and probably also CPDs containing cytosine, are replicated in vivo in a largely accurate manner by a DNA polymerase eta (Pol eta) dependent process. Pol eta is a DNA damage-tolerant and error-prone DNA polymerase encoded by the POLH (XPV) gene in humans. Another member of the Y family of error-prone DNA polymerases is POLI encoding DNA polymerase iota (Pol iota). In order to clarify the specific role of Pol iota in UV mutagenesis, we have used an siRNA knockdown approach in combination with a supF shuttle vector which replicates in mammalian cells, similar as we have previously done for Pol eta. Synthetic RNA duplexes were used to efficiently inhibit Pol iota expression in 293 T cells. The supF shuttle vector was irradiated with 254 nm UVC and replicated in 293 T cells in presence of anti-Pol iota siRNA. Surprisingly, there was a consistent reduction of recovered plasmid from cells with Pol iota knockdown and this was independent of UV irradiation of the plasmid. The supF mutant frequency was unchanged in the siRNA knockdown cells relative to control cells confirming that Pol iota does not play an important role in UV mutagenesis. UV-induced supF mutants were sequenced from siRNA-treated cells and controls. Neither the type of mutations nor their distribution along the supF gene were significantly different between controls and siRNA knockdown cells and were predominantly C to T and CC to TT transitions at dipyrimidine sites. These results show that Pol iota has no significant role in UV lesion bypass and mutagenesis in vivo and provides some initial data suggesting that this polymerase may be involved in replication of extrachromosomal DNA.

Base Sequence↗