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Results for “Extrachromosomal DNA”

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PubMed2001

Effect of overexpression of LAS17 on stress tolerance and the stability of extrachromosomal DNA in Saccharomyces cerevisiae.

The effects of the overexpression of LAS17/BEE1, which encodes a yeast protein exhibiting sequence homology to the Wiscott-Aldrich syndrome protein, on the cell growth of Saccharomyces cerevisiae were examined. Sake yeast strain UT-1 grows at a faster rate as a result of the overexpression of LAS17 than control cultures under various stresses such as high temperature, high ethanol concentration, and oxidative stress, and the tolerance to these stresses was increased compared with the control. Moreover, a high cell survival rate was attained with overexpression of LAS17, when cells in the stationary phase of the growth cycle were subjected to heat killing (48 degrees C) or ethanol killing (20% v/v). In addition, the rate of induction of rho- was markedly reduced by overexpression of LAS17 when serine, tyrosine, and aspartic acid were used as N sources and the yeast was cultured at 35 degrees C, while rho- strains in control cultures were induced at a high frequency. After the incubation of cells harboring a multicopy vector in YPD or synthetic complete medium, almost all of the cells inherited the vector at about 15 copies per cell as a result of the overexpression of LAS17, whereas the cells harboring the control vector accounted for only 15% of the total number of cells. These results suggest that Las17p might be a multifunctional protein involved in cell growth regulation, extrachromosomal DNA transportation and stress responses.

Journal Article↗
PubMed1984

Slow virus visna: reproduction in vitro of virus from extrachromosomal DNA.

Under permissive conditions of growth in tissue culture, the retrovirus visna multiples over the course of a few days to high titer and kills the host cell. We show that in this lytic life cycle, viral DNA is tightly associated with, but not covalently linked to, chromosomal DNA. This finding provides explanations for a number of the unusual properties of the lentivirus subfamily of retroviruses, and suggests potential mechanisms for the block in virus gene expression in vivo responsible for the slow infection in nature.

DNA Replication↗
PubMed2000

Detection of same sized 4.3 Kb extrachromosomal DNA elements in weakly beta-haemolytic human intestinal spirochaetes and Serpulina pilosicoli of swine origin.

Agarose gel electrophoresis of total DNA from Italian strains of weakly beta-haemolytic human intestinal spirochaetes (w beta HIS) and porcine Serpulina pilosicoli reference strain P43/6/78 showed an extrachromosomal band having the same size and migrating at 4.3 Kb. The same results were observed after agarose gel electrophoresis of DNA obtained from the supernatant fluids of the spirochaetal cultures analysed. Swine Serpulina hyodysenteriae reference strain P18A was comparatively analysed and a 6.5 Kb extrachromosomal DNA element was found, as expected. Furthermore, S. hyodysenteriae reference strain P18A differed from all the other spirochaetes tested and had a higher number of flagella (8-12) at each cell end and was strongly beta-haemolytic. To the best of our knowledge, this is the first report on the detection of a band of extrachromosomal DNA having the same size in w beta HIS and S. pilosicoli from swine origin.

Animals↗
PubMed1985

The linear extrachromosomal DNA of Physarum polycephalum replicates and is maintained under non-selective conditions in two different lower eukaryotes.

The slime mould Physarum polycephalum contains 100 to 200 molecules of extrachromosomal linear DNA (PeDNA). Two sets of the 19S and 26S ribosomal genes are located on each molecule of PeDNA. In the nonmitotic phase of the cell cycle PeDNA is localised in the nucleolus. The molecules are maintained throughout vegetative growth. In order to study the signals responsible for its maintenance, PeDNA was purified and introduced into the two distantly related yeasts Saccharomyces cerevisiae and Schizosaccharomyces pombe. Surprisingly, intact PeDNA transforms both yeasts with high frequency and PeDNA sequences are maintained in the absence of selective pressure.

Chromosomes↗
PubMedDate not supplied

Amplification of inter-Alu extrachromosomal DNA during cellular ageing: retraction and explanation.

We reported previously the age-dependent appearance of extrachromosomal circular DNA bands hybridizing to a human DNA fragment ('inter-Alu'), isolated from a genomic cluster of AluI repeats. Such bands appeared or increased at late passage in four out of six human fibroblast strains (six out of nine cell expansions); moreover, all DNAs (9/9) obtained from peripheral lymphocytes of aged donors, but none (0/8) from young donors, revealed a non-genomic inter-Alu band at congruent to 4.8 kilobases (kb). Subsequent data extended these numbers to 16/24 aged donors compared with 0/18 young donors. These results were interpreted as evidence of age-dependent DNA rearrangement in normal human cells. We now report that the 'extra' bands were of microbial origin, although clearly occurring in an age-dependent manner.

Aged↗
PubMed1993

Evidence for binding of extrachromosomal DNA sequences to nuclear matrix proteins in multidrug-resistant KB-V1 cells.

Multidrug-resistant KB-V1 cells carry amplified mdrl gene sequences located in an extrachromosomal compartment (on episomes). Since episomes do not contain centromeric or telomeric sequences it is unclear whether they are able to bind to nuclear matrix proteins that may regulate episomal gene expression. Using high salt treatments followed by in situ hybridization and dot blot analyses we found evidence for direct binding of episomal DNA to nuclear matrix proteins. This binding could only be reversed after incubation with trypsin or proteinase K as determined by contour-clamped homogeneous electric field (CHEF) electrophoresis. Our findings are consistent with the concept that circular extrachromosomal DNA may not only reintegrate into nuclear DNA but may also be subject to functional control by regulatory proteins within the nuclear matrix.

Cell Line↗
PubMed2001

Granulocytic differentiation of HL-60 cells, both spontaneous and drug-induced, might require loss of extrachromosomal DNA encoding a gene(s) not c-MYC.

Treatment of HL-60 cells with drugs induces granulocytic differentiation and c-MYC down-regulation that is irreversible and associated with loss of DNase I-hypersensitive sites in c-MYC promoter. The expression of these phenotypes requires a slow process that appears to accompany a loss of c-MYC copies in double minutes via micronuclei. However, the drug treatment induced c-MYC down-regulation very early, though only reversibly. Here we show that we can resolve this paradox by assuming a gene(s) in other extrachromosomal, acentromeric DNA. Treatment with drugs might induce no down-regulation of this gene, but its complete elimination via micronuclei might be necessary and sufficient for the expression of the above phenotypes. Loss of c-MYC copies is unavoidable because the exclusion of extrachromosomal DNAs via micronuclei is at random. This conclusion is based on the observation of a substantial number of c-MYC copies in certain differentiated cells, irrespective of whether the differentiation was induced with drugs or without.

Cell Differentiation↗
PubMed1999

The "small" polydisperse cytoplasmic extrachromosomal DNA of chicken leukaemic myeloblasts and the avian myeloblastosis virus core-bound DNA seem to descend from origin regions of chromosomal DNA replication.

Nucleotide sequences are presented for 12, 7 and 12 cloned extrachromosomal DNAs by nature harbored in nucleoprotein (NP) complexes forming chicken leukaemic myeloblast (CHLM) post microsomal sediment (POMS) components A, B and C, respectively, and for 11 cloned avian myeloblastosis virus (AMV) DNAs. Analysis of the abundance of sequence motifs significant for eukaryotic chromosomal DNA replication origin (ori) regions (and their initiation zones) has shown that these DNAs are reminiscent of cell DNA fragments enriched in ori sequences (Rao et al., 1990) and/or sequence features of several eukaryotic chromosomal oris containing clusters of modular sequence elements (Dobbs et al., 1994). Accordingly, these DNAs, with an (A + T) content prevalently higher than that of the total cell DNA, revealed the presence of asymmetrically distributed (A + T)-rich stretches, scaffold attachment region (SAR) T consensuses, polypyrimidine nucleotide (poly(Py)) tracts and minimal Saccharomyces cerevisiae autonomously replicating sequence (ARS) consensus, in abundance comparable with that of these sequences of DNA fragments enriched in oris. All these DNAs were found to be enriched also in sequence elements held as primase (Pr) attachment sites. Moreover, DNAs of POMS component B and those of AMV DNA were found to be enriched in the asymmetric pyrimidine (Py) heptanucleotide motif of Waltz et al. (1996) occurring in the initiation zones of ori region. Consequently, these extrachromosomal DNAs, portion of which represents a precursor of AMV DNA, seem to descent from initiation zones of various ori regions of an early replicating chromosomal myeloblast DNA. In addition, a possible explanation of the inclination of these DNAs to form multimers is presented.

Animals↗
PubMed1997

An additional mechanism of ribosome-inactivating protein cytotoxicity: degradation of extrachromosomal DNA.

Inhibition of protein synthesis by cleavage of the N-glycosidic bond of a specific adenine of 28 S rRNA has been accepted as the mechanism by which plant ribosome-inactivating proteins (RIPs) cause cytotoxicity. The cytotoxic action of gelonin on Plasmodium falciparum malaria parasites appears to occur by a different mechanism. Parasite intoxication, which is manifested by mitochondrial dysfunction and lack of nucleic acid synthesis in the erythrocytic cycle following exposure to the toxin, is caused by the elimination of the parasite 6 kb extrachromosomal (mitochondrial) DNA. This is the first report which demonstrates that the DNA-damaging activities of RIPs observed in vitro can contribute to their cytotoxicity.

Animals↗
PubMed1991

Cloning and detection of chromosomal and extrachromosomal DNA from mycoplasmalike organisms that cause yellow dwarf disease of rice.

DNA was extracted from rice plants infected with mycoplasmalike organisms (MLOs) causing yellow dwarf disease. DNA of the causal agent was separated from the host DNA by repeated bisbenzimide-CsCl equilibrium density gradient centrifugations. MLO DNA cut by HindIII was ligated into plasmid Bluescript II and cloned in Escherichia coli NM522. The DNA inserts were labeled with peroxidase and employed as probes in hybridization. Southern analysis revealed that the insert in pRYD-12 consisted of one, presumably chromosomal, piece of MLO DNA, whereas the insert in pRYD-19, another recombinant plasmid, consisted of one, presumably extrachromosomal, piece of MLO DNA. Cloned DNA probes were successfully applied in dot blot hybridization for the detection of rice yellow dwarf disease MLOs in rice plants and in an insect vector, the green rice leafhopper (Nephotettix cincticeps).

Journal Article↗
PubMed2006

Extrachromosomal DNA isolated from tomato big bud and Candidatus Phytoplasma australiense phytoplasma strains.

The nucleotide sequences of two extrachromosomal elements from tomato big bud (TBB) and one extrachromosomal element from Candidatus Phytoplasma australiense (Ca. P. australiense) phytoplasmas were determined. Both TBB plasmids (3319 and 4092 bp) contained an open reading frame ( approximately 570 bp) with homology to the rolling circle replication initiator protein (Rep). This gene was shorter than the rep genes identified from other phytoplasma plasmids, geminiviruses and bacterial plasmids. Both TBB extrachromosomal DNAs (eDNAs) encoded a putative DNA primase (dnaG) gene, a chromosomal gene required for DNA replication and which contains the conserved topoisomerase/primase domain. We speculate that the replication mechanism for the TBB phytoplasma eDNA involves the dnaG gene instead of the rep gene. The Ca. P. australiense eDNA (3773 bp) was shown to be circular and contained four open reading frames. The rep gene was encoded on ORF 1 and had homology to both plasmid (pLS1) and geminivirus-like domains.

Amino Acid Sequence↗