Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Mitochondrial DNA replication”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

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

At least 109 records · Page 6Linked to original sources
PubMed1975

Probable synchronous replication of mitochondrial DNA in cultures of chick embryo fibroblasts.

Cultures of chick embryo fibroblasts were synchronized using a procedure previously described. The profile of incorporation of tritiated thymidine showed a main peak of nuclear DNA replication followed by a small peak between 18 and 24 hr after induction of the cell division, and representing 10 to 25% of the main peak. To identify this small peak, cells were treated with ethidium bromide(EB) chloramphenicol (CAP) or 9-B-D arabinofuranosyl adenine (Ara-A). When EB (1 mug ml-1) and CAP(25mug ml-1) were added at time of induction of mitosis (T0) or 14 hr later (T14) the small peak was suppressed whereas the main peak was not decreased. On the contrary, only the main peak was suppressed when Ara-A was added at T0 or T14. These results suggest that the peak might correspond to the synchronous replication of the mitochondrial DNA during the G2 and M phases of the cell division cycle.

Animals↗
PubMed2005

Oxygen-induced mitochondrial biogenesis in the rat hippocampus.

The hypothesis that damage to mitochondrial DNA by reactive oxygen species increases the activity of nuclear and mitochondrial transcription factors for mitochondrial DNA replication was tested in the in vivo rat brain. Mitochondrial reactive oxygen species generation was stimulated using pre-convulsive doses of hyperbaric oxygen and hippocampal mitochondrial DNA content and neuronal and mitochondrial morphology and cell proliferation were evaluated at 1, 5 and 10 days. Gene expression was subsequently evaluated to assess nuclear and mitochondrial-encoded respiratory genes, mitochondrial transcription factor A, and nuclear respiratory transcription factors-1 and -2. After 1 day, a mitochondrial DNA deletion emerged involving Complex I and IV subunit-encoding regions that was independent of overt neurological or cytological O(2) toxicity, and resolved before the onset of cell proliferation. This damage was attenuated by blockade of neuronal nitric oxide synthase. Compensatory responses were found in nuclear gene expression for manganese superoxide dismutase, mitochondrial transcription factor A, and nuclear respiratory transcription factor-2. Enhanced nuclear respiratory transcription factor-2 binding activity in hippocampus was accompanied by a nearly three-fold boost in mitochondrial DNA content over 5 days. The finding that O(2) activates regional mitochondrial DNA transcription, replication, and mitochondrial biogenesis in the hippocampus may have important implications for maintaining neuronal viability after brain injury.

Animals↗
PubMed1972

Replication of mitochondrial DNA in mouse L cells and their thymidine kinase - derivatives: displacement replication on a covalently-closed circular template.

Thymidine kinase(-) lines of mouse L cells incorporate thymidine exclusively into mitochondrial DNA. This fact permits assessment of labeled mitochondrial DNA components in ethidium bromide-cesium chloride gradients. Contaminating nuclear DNA is unlabeled and need not be removed. Elimination of the DNase treatment of purified mitochondria reveals that the replicative forms that exhibit displacement replication up to full genome size are covalently-closed circular molecules. Denaturation followed by brief renaturation of these larger replicating molecules produces closed-circular DNA with a deficiency of Watson-Crick turns, appearing as single-strand loops. This result suggests that displacement replication proceeds with nicking and rapid closure of the covalently-closed circular template.

Animals↗
PubMed2006

Replication of vertebrate mitochondrial DNA entails transient ribonucleotide incorporation throughout the lagging strand.

Using two-dimensional agarose gel electrophoresis, we show that mitochondrial DNA (mtDNA) replication of birds and mammals frequently entails ribonucleotide incorporation throughout the lagging strand (RITOLS). Based on a combination of two-dimensional agarose gel electrophoretic analysis and mapping of 5' ends of DNA, initiation of RITOLS replication occurs in the major non-coding region of vertebrate mtDNA and is effectively unidirectional. In some cases, conversion of nascent RNA strands to DNA starts at defined loci, the most prominent of which maps, in mammalian mtDNA, in the vicinity of the site known as the light-strand origin.

5' Flanking Region↗
PubMed1986

Both the conserved stem-loop and divergent 5'-flanking sequences are required for initiation at the human mitochondrial origin of light-strand DNA replication.

Mammalian mitochondrial DNAs contain a conserved origin of light-strand replication that supports accurate initiation of DNA synthesis in vitro. This provides an opportunity to examine the sequence requirements for initiation through in vitro analysis of a series of deleted and mutagenized DNA templates. These assays use enzymes isolated from human mitochondria and single-stranded DNA templates containing deletions or substitutions in the known origin region. The data indicate that accurate and efficient light-strand replication in vitro requires the previously identified stem-loop structure located within a tRNA cluster. In addition, the template sequence 3'-GGCCG-5', located immediately adjacent to the stem, is necessary for efficient replication. This sequence, the complement of which encodes the 3' end of tRNACys, may be the site of transition from RNA primer synthesis to DNA synthesis. Surprisingly, substitutions within a region located in the loop of this origin do not reduce levels of replication.

Base Sequence↗
PubMed2003

Endonuclease G is required for early embryogenesis and normal apoptosis in mice.

Endonuclease G (EndoG) is a nuclear-encoded mitochondrial protein reported to be important for both nuclear DNA fragmentation during apoptosis and mitochondrial DNA replication. To evaluate the in vivo function of EndoG, we have investigated the effects of EndoG deficiency in cells and mice. We found that EndoG homozygous mutant embryos die between embryonic days 2.5 and 3.5. Mitochondrial DNA copy numbers in ovulated oocytes from EndoG heterozygous mutant and wild-type mice are similar, suggesting that EndoG is involved in a cellular function unrelated to mitochondrial DNA replication. Interestingly, we found that cells from EndoG heterozygous mutant mice exhibit increased resistance to both tumor necrosis factor alpha- and staurosporine-induced cell death. Moreover, spontaneous cell death of spermatogonia in EndoG heterozygous mutant mice is significantly reduced compared with wild-type mice. DNA fragmentation is also reduced in EndoG+/- thymocytes and splenocytes compared with wild-type cells, as well as in EndoG+/- thymus in vivo compared with that of the wild-type mice, on activation of apoptosis. These findings indicate that EndoG is essential during early embryogenesis and plays a critical role in normal apoptosis and nuclear DNA fragmentation.

Animals↗
PubMed1994

Peripheral benzodiazepine stimulates secretion of growth hormone and mitochondrial proliferation in pituitary tumour GH3 cells.

High affinity receptors for peripheral benzodiazepines (PBD) are present within the pituitary gland. Whether these receptors influence cell growth, mitochondrial morphology and secretion of growth hormone was examined in pituitary tumour GH3 cells. Cells were incubated in medium with either 10% calf serum, or serum free medium, or serum free medium plus 10 nM of selective PBD ligands (PK11195 or Ro5-4864) or a central benzodiazepine ligand (clonazepam). Peripheral or central ligands had no effect on cell growth. Quantitative electron micrography, however, revealed that cells treated with PBDs had a 2.5-fold increase in the total mitochondrial area within cells, a 1.6-fold increase in the number of mitochondria, and a 2.0 to 2.7-fold increase on the number of dividing mitochondria compared to serum free controls. The activity of DNA polymerase gamma, which replicates mitochondrial DNA, was increased approximately 3 times the initial value after 6 h exposure to PBDs. The number of nucleolar organizer regions (NORs), which relate to the ultimate synthesis of cellular protein, showed a 1.4-fold increase in PBDs treated cells. Secretion of growth hormone was stimulated (240% of serum free control) by exposure to PBDs for 12 h. The central benzodiazepine ligand, clonazepam, had little effect on mitochondrial morphology or secretion of growth hormone. These findings suggest that PBD receptors may be involved in mitochondrial proliferation and may affect the secretion of pituitary hormones.

Adenoma↗
PubMed1999

1-Methyl-4-phenylpyridinium ion (MPP+) selectively inhibits the replication of mitochondrial DNA.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine is known to cause Parkinsonism in its neurotoxic form, 1-methyl-4-phenylpyridinium ion (MPP+). We have previously reported that MPP+ decreases the content of mitochondrial DNA (mtDNA) independently of the inhibition of complex I in human cells [Miyako, K., Kai, Y., Irie, T., Takeshige, K., and Kang, D. (1997) J. Biol. Chem. 272, 9605-9608]. Here we study the mechanism causing the decrease in mtDNA. MPP+ inhibits the incorporation of 5-bromo-2'-deoxyuridine into mtDNA but not into nuclear DNA, indicating that MPP+ inhibits the replication of mtDNA but not that of the nuclear genome. The replication of mtDNA is initiated by the synthesis of the heavy strand switched from the transcription of the light strand. MPP+ decreases the nascent heavy strands per mtDNA and increases the transcript of the ND6 gene, encoded on light strand, per mtDNA. The amount of mitochondrial transcription factor A is not decreased. These data suggest that the transcription is not inhibited and therefore the transition from transcription to replication of mtDNA is lowered in the MPP+-treated cells. Electron microscopy shows that the number of mitochondria is not decreased in the MPP+-treated cells, suggesting that MPP+ does not affect the overall biogenesis of mitochondria. Thus, MPP+ selectively inhibits the replication of mtDNA.

1-Methyl-4-phenylpyridinium↗
PubMed1975

Replication of mitochondrial DNA. Selective inhibition of the H-strand synthesis in isolated mitochondria by sibiromycin.

Sibiromycin, an antitumour antibiotic forming a stable complex with the double-stranded DNA selectively inhibits the incorporation of [3H]thymidine into the H-strand of mtDNA during the incubation of isolated rat liver mitochondria in vitro. A model accounting for this result is presented. It is concluded that the H-strand is a leading strand throughout mtDNA replication adn consequently the replication of rat liver monomer mtDNA is unidirectional.

Animals↗
PubMed1988

Replication of mitochondrial DNA in the gonadotropin-primed corpus luteum of the rat.

The effect on mitochondria isolated from corpus luteal tissues following priming of immature female rats with pregnant mares serum gonadotropin (PMSG) and human chorionic gonadotropin (hCG) was studied. Ultrastructural studies showed intramitochondrial filamentous nucleic acid networks in situ following intense uranyl acetate staining. The intramitochondrial complexes were sensitive to nuclease treatment. Primed corpora lutea contained a 3.7-fold increase of mitochondrial DNA (mtDNA) per mg of mitochondrial protein when compared to unprimed ovaries. In subsequent experiments female rats were injected with 3H-thymidine 12 h before harvesting gonadotropin-primed corpora lutea from which mitochondria were isolated, purified and lysed. MtDNA was isolated and purified from the lysate by CsCl-ethidium bromide equilibrium buoyant density gradient centrifugation. Both the upper and lower bands of mtDNA as well as the intermediate region of the gradient contained radioactive label. When mtDNA from a fractionated gradient was mounted for electron microscopy and examined, replicative forms of mtDNA were observed. The mechanism of replication appears to be by the displacement-loop model of mtDNA replication. Ultrastructural as well as biochemical evidence indicate that a consequence of corpora lutea formation is the replication of mtDNA.

Animals↗
PubMed1974

Cleavage of replicating forms of mitochondrial DNA by EcoRI endonuclease.

Digestion of mouse L cell mitochondrial DNA with EcoRI restriction endonuclease produces two linear duplex fragments comprising 86.3 +/- 2.0% and 14.2 +/- 1.0% of the circular genome length (16,000 +/- 470 nucleotide pairs). Digestion of human HeLa cell mitochondrial DNA with EcoRI produces three linear duplex fragments comprising 49.2 +/- 1.0%, 44.4 +/- 0.9%, and 6.4 +/- 0.4% of the circular genome length (16,590 +/- 710 nucleotide pairs). These fragments are shown to be generated by cleavage in unique regions of the mouse and human mitochondrial DNAs. An electron microscopic analysis of partially replicated molecules cleaved by EcoRI establishes a unidirectional mode of DNA replication for L cell mitochondrial DNA. The origin for DNA replication is located on the larger EcoRI fragment at a position that is 1,890 +/- 250 nucleotide pairs (11.8 +/- 1.2% of the circular genome length) from the proximal restriction site. Replication proceeds unidirectionally away from this restriction site throughout the length of the larger EcoRI fragment. Analysis of L cell, D-loop mitochondrial DNA cleaved by EcoRI indicates that a unique sequence is synthesized in formation of the D-loop in these nonreplicating molecules. The origin of D-loop synthesis is located on the larger EcoRI fragment at a position 1,760 +/- 180 nucleotide pairs (11.0 +/- 1.1% of the circular genome length) from the proximal restriction site and is, therefore, the origin for unidirectional displacement replication.

Animals↗
PubMed1992

Structure and function of the mitochondrial genome.

It is now clear that molecular defects in human mitochondrial DNA play a significant role in human disease. Mitochondrial DNA mutations range from single base changes in the 16.5 kilobase-pair genome up to large deletions and rearrangements. Independently of the actual cause of a given mutation, it is possible to predict at least some of the consequences of changes in mitochondrial DNA sequence. This paper reviews our overall understanding of the mode and mechanism of mitochondrial DNA replication and transcription and how this relates to mitochondrial gene expression. This provides a background to anticipate the nature and extent of mitochondrial DNA sequence changes that might be of physiological consequence.

Animals↗
PubMed1993

Mitochondrial DNA of Chlamydomonas reinhardtii: the structure of the ends of the linear 15.8-kb genome suggests mechanisms for DNA replication.

The mitochondrial genome of Chlamydomonas reinhardtii is a linear double-stranded DNA of 15.8 kb. With the exception of the termini its DNA sequence has been published. Here we describe the unique structure of the two termini determined from cloned fragments or, for the very terminal sequences, by the Maxam and Gilbert method after 5' labeling of uncloned terminal fragments. The 15.8-kb DNA is characterized by terminal inverted repeats of 531 or 532 bp in length including long 3' extensions. The 3' single-stranded extensions of the left and right ends are non-complementary, identical in sequence, and comprise 39 to 41 nucleotides. Remarkably, the linear genome possesses in addition an internal 86-bp repeat of the two outermost sequences. The unusual structure of the 15.8-kb DNA termini is compared with those of other linear mitochondrial DNAs. Possible mechanisms of 15.8-kb DNA replication are discussed.

Animals↗