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At least 361 records · Page 20Linked to original sources
PubMed1979

Isolation and partial characterization of the multiple forms of deoxyribonucleic acid-dependent ribonucleic acid polymerase in the fungus Podospora anserina.

Three DNA-dependent RNA polymerases have been isolated and partially purified from the mycelium of the fungus Podospora anserina. Separated by DEAE-Sephadex chromatography, they have been designated RNA polymerases I, II, and III according to their order of elution. Their catalytic properties and alpha-amanitin sensitivity are in agreement with those of the homologous enzymes found in other eukaryotic organisms. The three enzymes exhibit rather sharp monophasic ammonium sulfate dependence with optima which are, respectively, 0.035 M, 0.050 M, and 0.075 M. Enzyme I has the largest Mn2+/Mg2+ activity ratio, shows a marked preference for native DNA, and is insensitive to alpha-amanitin. Enzyme III uses poly(dA-dT) in preference to native DNA as template and is only partially sensitive to alpha-amanitin. Enzyme II is sensitive to alpha-amanitin, but high concentrations of the toxin are required for inhibition compared to other eukaryotic class II enzymes. Three similar RNA polymerases with comparable levels of activity were found in the temperature-dependent VR strain when cellular incompatibility, leading to a rapid cessation of RNA synthesis, was induced.

Amanitins↗
PubMed1982

Separate binding sites on rat liver ribosomal protein L6 for 5 S and 5.8 S ribosomal ribonucleic acids and for transfer ribonucleic acids.

The rat liver ribosomal protein L6 binds to 5 S and 5.8 S rRNAs, and to initiator and elongator tRNAs. Experiments were carried out to determine if the protein has separate domains for binding each of these nucleic acids. For that purpose, nucleic acid.L6 complexes were immobilized on Sepharose and their capacity to retain 32P-labeled nucleic acids was assessed. A 5 S rRNA.L6 affinity complex binds 5.8 S [32P]rRNA indicating that L6 has separate binding sites for 5 S and 5.8 S rRNAs. A 5 S rRNA.L6 affinity complex also binds [32P]tRNAPhe, and unlabeled 5.8 S rRNA does not compete with the radioactive tRNA for binding to L6, suggesting that the ribosomal protein has a third, distinct, nucleic acid-binding domain. To determine if L6 has separate sites for the binding of elongator and initiator tRNAs, tRNAPhe. L6 and tRNAfMet.L6 affinity columns were constructed. The tRNAPhe.L6 affinity complex binds [32P]tRNAfMet, and the tRNAfMet.L6 complex binds [32P]tRNAPhe, suggesting there are distinct sites on L6 for the interaction with initiator and elongator tRNAs; however, competition experiments imply that, while there are two sites for binding tRNAs to L6, the sites do not discriminate between initiator and elongator tRNAs.

Animals↗
PubMed1996

Human papillomavirus deoxyribonucleic acid and ribonucleic acid in seminal plasma and sperm cells.

OBJECTIVE: To investigate the possible presence and expression of human papillomavirus viruses (HPV) in human plasma and sperm cells. DESIGN: Controlled clinical study. SETTING: A major medical center affiliated with a medical college. PATIENTS: Twenty-four randomly selected patients who attended Fertility Clinics at the Chang Gung Memorial Hospital. INTERVENTIONS: Specimens of semen were collected from volunteered patients MAIN OUTCOME MEASURE: The presence of HPV types 16 and 18 DNA and RNA sequences were examined by polymerase chain reaction. RESULTS: Human papillomavirus type 16 E6 and E7 DNA and RNA sequences were found in two and zero seminal plasma specimens, respectively, and in six and two sperm cells specimens, respectively. Deoxyribonucleic acid and RNA sequences of HPV type 18 were found in eight and two seminal specimens and in 11 and 5 sperm cells specimens, respectively. CONCLUSION: These results seem to suggest that HPV cannot only infect human sperm cells, certain HPV genes are expressed actively in infected sperm cells. The virus-infected sperm cells conceivably can behave as vectors or carriers for the transmission of HPV, to sexual partner during sexual contact, to fetuses through fertilized eggs, or both.

Base Sequence↗
PubMed1976

Purification and subunit structure of deoxyribonucleic acid-dependent ribonucleic acid polymerase III from the posterior silk gland of Bombyx mori.

DNA-dependent RNA polymerase III was purified from the posterior silk gland of the moth Bombyx mori by chromatography on DEAE-cellulose, DEAE-Sephadex, CM-Sephadex, and phosphocellulose and by sedimentation in sucrose density gradients. The specific activity of this chromatographically homogeneous enzyme was comparable to that reported for other purified eukaryotic RNA polymerases. Sucrose gradient sedimentation analysis suggested a molecular weight of approximately 590,000 to 660,000 for B. mori RNA polymerase III. Analysis of subunit composition by polyacrylamide gel electrophoresis under denaturing conditions showed that the chromatographically purified RNA polymerase III contained subunits with molecular weights of 155,000 (IIIa), 136,000 (IIIb), 67,000 (IIIc), 62,000 (IIId), 49,000 (IIIe), 39,000 (IIIf), 36,000 (IIIg), 31,000 (IIIh), 28,000 (IIIi), and 18,000 (IIIj). Molar ratios were close to unity for all subunits except for IIIj, which was present in an approximate molar ratio of 2. As has been observed for mammalian class III enzymes, the B. mri RNA polymerase III can be resolved into two components upon electrophoresis under nondenaturing conditions. Comparative studies of the class III enzymes from B. mori and from higher eukaryotic cells show that many of the general chromatographic and catalytic properties, as well as the overall subunit compositions, are similar for the various enzymes. However, unlike the mammalian class III enzymes, B. mori RNA polymerase III is completely resistant to high concentrations of alpha-amanitin, and it does not contain an 89,000-dalton subunit. The data are discussed in terms of the function and regulation of RNA polymerase III in lower and higher eukaryotes.

Animals↗
PubMed1997

Seasonal dynamics of the tissue levels of total protein, free amino acid and ribonucleic acid in an Indian air-breathing teleost, Channa punctatus.

The tropical freshwater air-breathing teleost, Channa punctatus, reveals a seasonal metabolic reorganization with reference to its biochemical tissue compositions. The summer-adapted and winter-adapted C. punctatus seem to be two biochemically distinct populations. Besides, the different reproductive phases viz. prespawning, spawning, post-spawning, preparatory-I and preparatory-II are also biochemically distinct.

Acclimatization↗
PubMed1974

Non-continuous translation of coat protein and ribonucleic acid polymerase cistrons in MS2 bacteriophage ribonucleic acid.

In an MS2 phage ribonucleic acid (RNA)-directed in vitro protein-synthesizing system, the coat protein cistron and the adjacent RNA polymerase cistron are translated non-continuously. The ribosomes which have completed the synthesis of coat protein dissociate from the MS2 RNA and do not read through the intercistronic gap. Translation of the adjacent RNA polymerase cistron requires ribosomes other than those translating the coat protein cistron.

Amino Acids↗