Showing papers on "Mitochondrial DNA replication published in 2002"
TL;DR: Transgenic mice that selectively express in skeletal muscle a constitutively active form of calcium/calmodulin–dependent protein kinase IV showed augmented mitochondrial DNA replication and mitochondrial biogenesis, up-regulation of mitochondrial enzymes involved in fatty acid metabolism and electron transport, and reduced susceptibility to fatigue during repetitive contractions.
Abstract: Endurance exercise training promotes mitochondrial biogenesis in skeletal muscle and enhances muscle oxidative capacity, but the signaling mechanisms involved are poorly understood. To investigate this adaptive process, we generated transgenic mice that selectively express in skeletal muscle a constitutively active form of calcium/calmodulin-dependent protein kinase IV (CaMKIV*). Skeletal muscles from these mice showed augmented mitochondrial DNA replication and mitochondrial biogenesis, up-regulation of mitochondrial enzymes involved in fatty acid metabolism and electron transport, and reduced susceptibility to fatigue during repetitive contractions. CaMK induced expression of peroxisome proliferator-activated receptor gamma coactivator 1 (PGC-1), a master regulator of mitochondrial biogenesis in vivo, and activated the PGC-1 gene promoter in cultured myocytes. Thus, a calcium-regulated signaling pathway controls mitochondrial biogenesis in mammalian cells.
664 citations
TL;DR: It is shown that bona fide replication intermediates from highly purified mitochondria are essentially duplex throughout their length, but contain widespread regions of RNA:DNA hybrid, as a result of the incorporation of ribonucleotides on the light strand which are subsequently converted to DNA.
288 citations
TL;DR: Evidence is presented that thymidine metabolism is altered in MNGIE and it is hypothesize that excessThymidine alters mitochondrial nucleoside and nucleotide pools leading to impaired mitochondrial DNA replication, repair, or both.
216 citations
TL;DR: Pol gamma was detected as one of the major oxidized mitochondrial matrix proteins, with a detectable decline in polymerase activity, which may result in a reduction in mitochondrial DNA replication and repair capacities.
Abstract: The mitochondrial respiratory chain is a source of reactive oxygen species (ROS) that are responsible for oxidative modification of biomolecules, including proteins. Due to its association with mitochondrial DNA, DNA polymerase gamma (pol gamma) is in an environment to be oxidized by hydrogen peroxide and hydroxyl radicals that may be generated in the presence of iron ions associated with DNA. We tested whether human pol gamma was a possible target of ROS with H2O2 and investigated the effect on the polymerase activities and DNA binding efficiency. A 1 h treatment with 250 microM H2O2 significantly inhibited DNA polymerase activity of the p140 subunit and lowered its DNA binding efficiency. Addition of p55 to the p140 catalytic subunit prior to H2O2 treatment offered protection from oxidative inactivation. Oxidatively modified amino acid residues in pol gamma resulting from H2O2 treatment were observed in vitro as well as in vivo, in SV40-transfected human fibroblasts. Pol gamma was detected as one of the major oxidized mitochondrial matrix proteins, with a detectable decline in polymerase activity. These results suggest pol gamma as a target of oxidative damage, which may result in a reduction in mitochondrial DNA replication and repair capacities.
181 citations
TL;DR: The structure of dNT-2 is solved, the first of a mammalian 5′ nucleotidase and reveals a relationship to the HAD family, members of which use an aspartyl nucleophile as their common catalytic strategy, with a phosphoserine phosphatase as the most similar neighbor.
Abstract: 5′ nucleotidases are ubiquitous enzymes that dephosphorylate nucleoside monophosphates and participate in the regulation of nucleotide pools. The mitochondrial 5′-(3′) deoxyribonucleotidase (dNT-2) specifically dephosphorylates dUMP and dTMP, thereby protecting mitochondrial DNA replication from excess dTTP. We have solved the structure of dNT-2, the first of a mammalian 5′ nucleotidase. The structure reveals a relationship to the HAD family, members of which use an aspartyl nucleophile as their common catalytic strategy, with a phosphoserine phosphatase as the most similar neighbor. A structure-based sequence alignment of dNT-2 with other 5′ nucleotidases also suggests a common origin for these enzymes. Here we study the structures of dNT-2 in complex with bound phosphate and beryllium trifluoride plus thymidine as model for a phosphoenzyme–product complex. Based on these structures, determinants for substrate specificity recognition and the catalytic action of dNT-2 are outlined.
80 citations
TL;DR: The N 6‐adenine DNA‐methyltransferase was isolated from the vacuolar vesicle fraction of wheat coleoptiles and seems to be responsible for mitochondrial DNA modification that might be involved in the regulation of replication of mitochondria in plants.
46 citations
TL;DR: It is established that dNT2 in vivo indeed is located in mitochondria and the native enzyme shows the same substrate specificity and affinity for inhibitors as the recombinant dNT1, and does not affect overall cellular deoxynucleotide turnover.
29 citations
TL;DR: Studies are discussed which may provide insight into the molecular mechanism for the stereochemical selectivity and differential toxicity of the isomeric 2',3'-dideoxy-3'-thiacytidine (3TC) and ddC compounds.
28 citations
TL;DR: Cybrid constructions revealed that the involvement of nuclear factor(s) in the generation of the length heteroplasmy is prominent in homopolymeric tract of eight cytosines.
Abstract: We have studied the genetic characteristics of a homopolymeric tract length heteroplasmy associated with the 16189C variant in the mtDNA D-loop control region to identify the factor(s) involved in the generation of the length heteroplasmy. The relative proportion of the various lengths of the polycytosines (i.e., the pattern of the length heteroplasmy) is maintained in an individual, and previous evidence shows that it is regenerated de novo following cell divisions. The pattern is maintained in maternally related individuals, suggestive of mtDNA determinants. Of the 38 individuals with the 16189C variant studied, 39% were found to exhibit the 16180AAACCCCCCCCCCC16193 variant associated with A16183C polymorphism [(11C)-group], while 53% showed the 16180AACCCCCCCCCCCC16193 variant associated with a further A16182C polymorphism [(12C)-group]. Haplotype analysis of the mtDNA revealed a specific association of the longer mean length of the poly[C] in the (12C)-group with haplogroup B. A similar association was also observed in the (11C)-group, but with a novel haplogroup. Cybrid constructions revealed that the involvement of nuclear factor(s) in the generation of the length heteroplasmy is prominent in homopolymeric tract of eight cytosines. The nuclearly coded factor(s) is/are presumably related to the fidelity of the nuclearly coded components of the mitochondrial DNA replication machinery.
26 citations
TL;DR: A 17-year-old male with neurologic and cardiovascular disorders characterized by complete atrioventricular block and a mitochondrial cytopathy with clinical, structural, biochemical, and molecular features shared by chronic progressive external ophthalmoplegia and Kearns-Sayre syndrome is described.
11 citations
TL;DR: RT-PCR experiments have demonstrated that this pseudogene (psi mtTFA) is transcribed in liver tissue and has a mosaic organization with six introns whose sizes the authors have calculated.
TL;DR: The computer modeling of the tertiary structure of P. lividus mtSSB shows a structure very similar to that experimentally determined for humanmtSSB, with the conservation of the main residues involved in protein tetramerization and in DNA binding.