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PubMed1975

Migration of ribosomes along the axons of the chick visual pathway.

The axoplasmic migration of ribosomes has been detected in the visual system of the chick. Monocular injection of radioactive uridine or an amino acid mixture was followed by sedimentation analysis in sucrose or cesium sulfate density gradients, of ribosomes prepared from the retinae of injected eyes and the left and right optic lobes. By this means both RNA and protein components of ribosomes were found to migrate from the retina to the innervated contralateral optic lobe. Following denervation of the distal nerve segment by eye removal, the stability of the transported RNA was reduced, suggesting its presynaptic location. The transport of RNA was not significantly imparied by intraocular injection of inhibitors of informational RNA or mitochondrial RNA synthesis prior to injection of radioactive uridine but was depressed by a low dose of actinomycin D.

Amanitins↗
PubMed1977

Quantitation of mitochondrial DNA, RNA, and protein in starved and starved-refed rat liver.

The purpose of this study was to investigate the problem of mitochondrial biogenesis in rat liver. The approach consisted of isolating mitochondria from control, 6 day starved and 6 day starved-5 day refed rats and comparing their DNA, RNA and protein content. This was performed by isolating the mitochondria by reorienting rate zonal centrifugation in sucrose gradients. It was found that six days of starvation resulted in a loss of 30% of the body weight, 55% of the liver weight, 40% of the mitochondrial protein, 60% of the mitochondrial RNA, but only 20% of the mitrochondrial DNA. It was also shown that refeeding of the rats for five days resulted in a restoration to normal or near normal levels in all the parameters measured. Further experiments employing the incorporation of 3H-TTP into into isolated mitochondria indicated that the maintenance of mitochondrial DNA was not the result of continuous DNA sythesis.

Animals↗
PubMed1979

Mitochondrial DNA, RNA, and protein synthesis in different regions of developing rat brain.

In vivo and in vitro (tissue slices) incorporation of labeled precursors into DNA, RNA, and proteins was measured in mitochondria obtained from cerebral hemispheres, cerebellum, and brain stem of rats at different days of postnatal development. To compare the synthesis of macromolecules in mitochondria with that in other subcellular fractions, the incorporation of labeled precursors into DNA, RNA, and proteins extracted from nuclei and into RNA and proteins extracted from microsomes and cytoplasmic soluble fractions was also measured. The results obtained showed that the incorporation of [3H]thymidine into DNA and of [14C]leucine into proteins of nuclei and mitochondria from the various brain regions examined decreased during postnatal development; however, at 30 days of age the specific radioactivity of mitochondrial DNA was higher than that of nuclear DNA. [3H]Uridine incorporation into RNA decreased from 10 to 30 days of age in nuclei while in mitochondria it was quite similar at both ages. This result may be due to a faster turnover of mitochondrial RNA compared to that of mitochondrial DNA and proteins. The results obtained suggest an active biosynthesis of macromolecules in brain mitochondria and might indicate an intense biogenesis of these organelles in rat brain during postnatal development.

Animals↗
PubMed1979

Fine structure of the 21S ribosomal RNA region on yeast mitochondria DNA. I. Construction of the physical map and localization of the cistron for the 21S mitochondrial ribosomal RNA.

1. We have used restriction enzyme analysis of petite mtDNAs to construct a detailed physical map of the 21S region on the mtDNA of the Saccharomyces cerevisiae strain JS1-3D. The map covers a segment of about 20,000 bp, on which the recognition sites of the enzymes HapII, HindII, HindIII, Sa1I, XhoI and HhaI have been localized (22 sites in total). This map has been checked in various ways against the independently constructed overall physical map of the mtDNA of strain JS1-3D. In addition, we have constructed a physical map with a resolution of about 200 bp of a HapII fragment of 1850 bp long, which carries the loci omega, RIB-1 and probably RIB-2. 2. The 21S rRNA hybridizes with the five adjacent HindII + III fragments TD9, DT19, TD15, DT14 and TT1, which lie in that order on the physical map of the 21S region. Of these, the two non-adjacent fragments TD9 and DT14 show a much stronger hybridization with 21S rRNA than DT19, TD15, and TT1. 3. The fragment DD5 (= DT19 + TD15) and part of DT14 belong to a sequence of about 1000 bp, which is absent from Saccharomyces carlsbergensis mtDNA. Although DD5 and DT14 show (very weak, respectively stronger) hybridization with 21S rRNA, the 1000 bp insert probably does not code for the 21S rRNA: the 21S rRNA of S. carlsbergensis comigrates with the 21S rRNA of JS1-3D on polyacrylamide gels under denaturing conditions. 4. Fragment DT14 hybridizes with the HindII + III fragment TD9, which shows the strongest hybridization with 21S rRNA. The presence of these sequence homologies has hampered the precise mapping of the 21S rRNA cistron. Our results are compatible, however, with the hypothesis that the sequences, coding for 21S rRNA, are located on HindII + III fragments that are not adjacent on JS1-3D mtDNA, namely TD9, DT14 and TT1.

DNA Restriction Enzymes↗
PubMed1979

Mapping and cloning of Neurospora crassa mitochondrial transfer RNA genes.

We have obtained collections of recombinant Escherichia coli plasmids containing restriction fragments of Neurospora crassa mitochondrial DNA cloned into pBR322. By hybridization of 32P end-labeled total mitochondrial tRNAs and seven different purified tRNAs to restriction digests of mitochondrial DNA and of recombinant plasmids carrying specific restriction fragments, we have located the tRNA genes on the mitochondrial DNA. We have found that the mitochondrial tRNA genes are present in two major clusters, one between the two ribosomal RNA genes and the second closely following the large rRNA gene. Only one of the two DNA strands within these clusters codes for tRNAs. All of the genes for the seven specific purified tRNAs examined--those for alanine, formylmethionine, leucine 1, leucine 2, threonine, tyrosine, and valine--lie within these clusters. Interestingly, the formylmethionine tRNA hybridizes to two loci within one of these gene clusters. We have obtained a fairly detailed restriction map of part of this cluster and have shown that the two "putative" genes for formylmethionine tRNA are not arranged in tandem but are separated by more than 900 base pairs and by at least two other tRNA genes, those for alanine and for leucine 1 tRNAs.

Base Composition↗
PubMed1977

Fine structure physical mapping of 4S RNA genes on mitochondrial DNA of Saccharomyces cerevisiae.

We have localized the genes for mitochondrial 4S RNA on the physical map of the mtDNA of several Saccharomyces cerevisiae strains by hybridization of iodinated 4S RNA to the restriction fragments obtained with endonucleases HindII + III, EcoRI and HapII. The data indicate that 5-8 of the 4S RNA genes are dispersed over a large area of the genome whereas the rest (about 18 genes) is located within an area of about 9000 bp in length (about 18 genes) is located within an area of about 9000 bp in length (about 12% of the genome) between the markers for chloramphenicol and paromomycin resistance (RIB 1 and PAR 1 loci). Within this region a cluster is present of 5 genes on a DNA fragment of 460 bp.

DNA↗
PubMed1975

Complex formation between nuclear RNA and mitochondrial proteins.

Specific proteins are present in mitochondria that are capable of forming complexes with nuclear RNA. Complex formation is time and temperature dependent and requires optimal conditions of Mg2+, K+ and H+ concentrations. The complexes are stable towards most denaturing agents and their component nucleic acids and proteins are resistant to nucleolysis and proteolysis respectively.

Animals↗
PubMedDate not supplied

[The regulator effect of fructose-1,6-diphosphate and cyclic adenosine monophosphate on protein and RNA synthesis by isolated mitochondria].

Effects of fructoso-1,6-diphosphate (FDP) and cyclic 3',5'-adenosine monophosphate (cAMP) on various steps of protein biosynthesis in isolated rat liver mitochondria were investigated. It was shown that FDP repressed and cAMP depressed the incorporation of both 14C-amino acid and [3H]uridine into mitochondrial polysomes. Cyclic 2',3'-adenosine monophosphate, a physiologically inactive analog of cAMP, had no depressing effect on the polysomes formation in mitochondria. Effects of FDP and cAMP on the synthesis of mitochondrial RNA at different periods of incubation (5, 10, 30 min) were studied. It was found that FDP repressed the high molecular weight mitochondrial RNA biosynthesis and prevented the mRNA formation. cAMP derepressed the FDP effect. Rifampicin prevented the derepressing action of cAMP. The rate of protein synthesis in the translation system isolated from mitochondria was affected neither by FDP nor by cAMP. Authors concluded that in the mammalian mitochondria the repression of protein synthesis by a glycolytic metabolite (FDP) and its derepression by cAMP represented regulatory mechanism acting at the transcription level like catabolite repression-derepression in microorganisms.

Animals↗
PubMed1977

Macromolecular synthesis and energy level in a mitochondrial conditional yeast mutant, tsm-8.

Mitochondrial DNA, protein and ATP syntheses persist at non-permissive temperature (35 degrees C) in the mitochondrial, conditionally rho- petites forming yeast mutant, tsm8. Protein and ATP syntheses, however, are diminished during prolonged incubation at 35 degrees C in non-fermentable substrate. Mitochondrial RNA synthesis decreases rapidly to a residual constant level of about 10% of the initial value after the shift to 35 degrees C. The decrease is reversed by returning to permissive conditions. Evidence is presented that this temperature-induced decrease in mitochondrial transcription rate is effected by a mutationally altered regulatory process rather than by temperature sensitivity of mitochondrial RNA polymerase. It is concluded that rho- petite formation in mutant tsm8 is not effected by complete inhibition of macromolecular and ATP syntheses but is correlated with a reduction in mitochondrial transcription.

Adenosine Triphosphate↗
PubMedDate not supplied

[Effect of hydrocortisone on the ribonucleic acid biosynthesis in the liver mitochondria, heart and spleen of rats with alloxan diabetes].

Mitochondrial RNA biosynthesis in diabetic rats under the influence of hydrocortisone (0.5 or 2 U per 100 g for 7 days) increased in the liver and decreased in the spleen. Heart mitochondrial RNA biosynthesis increased after hydrocortisone injection in a dose of 0.5 U per 100 g, but decreased after hormone administration in a dose of 2.5 U per 100 g. Thus, hydrocortisone played an important role in the changes of RNA biosynthesis in the liver, heart, and spleen mitochondria of diabetic animals.

Animals↗
PubMed1979

Regulation of the mitochondrial anabolism at low concentrations of thyroid hormones and by some of their structural analogues.

The Authors demonstrate that the in vitro stimulation of mitochondrial RNA synthesis produced by thyroid hormones takes place also at physiological levels, equal to those held in the liver cells of experimental animals. Two groups of male rats have been used: normal control animals (N) and animals surgically thyroidectomized on the 25th day of life (T). The animals were fed and kept in standard conditions and killed on the 85th day of life. The purification of mitochondrial samples and the determination of the mitochondrial RNA synthesis were carried out as previously described. The results suggest that the in vitro stimulation of mitocondrial RNA synthesis is already significant at the concentration of lnM. The trends are qualitatively comparable for either N or T animals. The structural analogues TRIAC (3,5,3'-triiodothyroacetic acid) and TRIPROP (3,5,3'-triiodothyropropionica acid) exhibit a clearly stimulatory effect on samples of N animals, while on samples of T animals is significant only for the first analogue. Similar trends are also observed on ADP/O ratio.

Adenosine Diphosphate↗
PubMed1976

Poly(A)-associated RNA from the mitochondrial fraction of the fungus Trichoderma.

Total RNA was extracted from purified mitochondrial and cytoplasmic fractions of germinating conidia of Trichoderma viride and bound to oligo(dT)-cellulose at 22 and 4 degrees C. Under chromatographic conditions which retained very short poly(A) segments (i.e., 4 degrees C), up to 10% of short-term 32PO4-lebeled RNA from the mitochondrial fraction were selectively bound. The poly(A)-associated RNAs from the mitochondrial and cytoplasmic fractions showed the following characteristics. (a) On polyacrylamide gels mitochondrial fraction RNA had a distinctive pattern with a major peak at about 22 S and a smaller one at about 29 S; in contrast, cytoplasmic fraction RNA was heterogenously distributed along the gel. (b) The poly(A) segment released by RNAase digestion of mitochondrial fraction poly(A)-associated RNA migrated on polyacrylamide gels as molecules 20-25-nucleotides long, while that of the cytoplasmic fraction showed an apparent size of 50-60 nucleotides. (c) Mitochondrial fraction RNA bound to oligo(dT)-cellulose in the cold had a guanine + cytosine content of 21% versus 34% for bulk mitochondrial RNA and 48% for cytoplasmic poly(A)-associated RNA; the oligo(dT)-bound RNAs were further identified by their high percentages of adenine residues (46% for the mitochondria and 30% for the cytoplasm). (d) The poly(A)-associated RNA fraction was translated, in vitro, in a cell-free protein-synthesizing system from wheat germ. The products induced by cytoplasmic RNA showed a complex pattern on polyacrylamide gels of many polypeptides ranging in molecular weights from 10000 to 40000. The pattern induced by mitochondrial fraction RNA however, was much simpler, revealing two discrete, main products: a major one at Mr approximately 13000 and a minor one at Mr approximately 20000.

Chromatography, Affinity↗
PubMed1975

Translation of RNA that contains polyadenylate from yeast mitochondria in an Escherichia coli ribosomal system.

RNA that contains poly(A) [poly(A)-RNA] has been isolated from yeast mitochondria by poly(U) Sepharose-4B column chromatography. Pulse-labeled poly(A)-RNA shows 8-10 discrete peaks by acrylamide gel electrophoresis. The specific activity of mitochondrial poly(A)-RAN is six to eight times greater than that of mitochondrial rRNA after pulse labeling of protoplasts with [3H-]uridine. Ethidium bromide inhibits incorporation by over 90%. The total mitochondrial RNA preparation was contaminated with 5-15% cytoplasmic rRNA as determined by gel electrophoresis, but RNA exhaustion hybridization experiments indicated little or no cytoplasmic contamination of the mitochondrial poly(A)-RNA. The poly(A)-RNA stimulates [3H]leucine incorporation into protein in an E. coli cell-free system. A fraction of the labeled product is precipitated with antibody directed toward yeast cytochrome oxidase, but not with antibody directed toward bovine serum albumin. Sodium dodecyl sulfate gel electrophoresis of the immunoprecipitated material reveals labeled peptides having the mobility of the three larger cytochrome oxidase peptides, which are known to be translated by mitochondrial ribosomes.

Cell-Free System↗
PubMed1977

RNA synthesis in mitochondria isolated from rat liver.

Mitochondrial RNA (mtRNA) was synthesized from purine and pyrimidine nucleosides in coupling with oxidative phosphorylation using isolated mitochondria. The in vivo synthesized mtRNA was adenine-uracil rich and sedimented at about 20 S by sucrose density gradient centrifugation. A major part of the newly synthesized mtRNA was shown to be poly (A)-containing RNA by the resistance to the digestion with pancreatic RNase and RNase T1 and the affinity to poly (U)-Sepharose columns or Millipore filters.

Animals↗
PubMed1976

Nucleic acids from subcellular fractions of N-nitrosodiethylamine-induced hepatoma in mice.

During eight successive isologous passages of hepatoma induced in male C3HA mice by N-nitrosodiethylamine, no common features of tumor progression were observed, although both the mitotic pattern and ploidy differed from generation to generation. These additional cytologic criteria allowed the biochemical examination of material least changed due to tumor progression. Tumor nDNA's were characterized by greater actinomycin D (AD)- and acridine orange (AO)-binding abilities than were normal nDNA's; this could have resulted from a higher proportion of double-stranded regions in tumor DNA. Isolated tumor deoxyribonucleoprotein had both lower template activity in an RNA polymerase system and fewer AD- and AO-binding sites, when compared with the activity and sites from normal mouse liver. RNA-DNA hybridization data with the above-mentioned findings showed that in hepatoma, part of the nuclear genome was repressed. Also, RNA "new classes" appeared and a certain proportion of nuclear genes controlling mitochondrial protein biosynthesis were derepressed in tumor mitochondria. The hybridization of mitochondrial RNA (mtRNA) and DNA revealed new classes of pulse-labeled RNA's in in vitro-incubated liver mitochondria that were absent from intact cell organelles; the hybridization properties of in vivo- and in vitro-formed hepatoma mtRNA's were similar. Competition and hybridization experiments demonstrated that in tumor mitochondria in vivo, some new classes of RNA existed. Hepatoma mitochondrial mRNA had a higher metabolic stability than did normal mRNA.

Acridines↗