RNA polymerases activation

Manganese ions enzyme activators, 6,578 probes, 6,563 RNA polymerases activation, 6, 585 transport microbes, 6, 569 plants, 6, 572 Manganese oxide colloidal... 

Escargueil AE, Poindessous V, Soares DG Sarasin A, Cook PR, Larsen AK. (2008) Influence of irofulven, a transcription-coupled repair-specific antitumor agent, on RNA polymerase activity, stability and dynamics in living mammalian cells. J Cell Sci 121 1275-1283. 

Pharmacology Rifampin inhibits DNA-dependent RNA polymerase activity in susceptible cells. Specifically, it interacts with bacterial RNA polymerase, but does not inhibit the mammalian enzyme. Cross-resistance has only been shown with other rifamycins. Rifampin at therapeutic levels has demonstrated bactericidal activity against intracellular and extracellular Mycobacterium tuberculosis organisms. Pharmacokinetics ... 

So far this class of carbazole alkaloids contains only two natural products, calothrixin A and its N-deoxy-derivative calothrixin B. These two pentacyclic metabolites with a quinolino[4,3- 7]carbazole-l,4-quinone framework displayed potent inhibitory effects on the in vitro growth of both human malarial parasites and human cancer cells and inhibition of RNA polymerase activity. Owing to this pharmaceutical potential, these natural products have attracted the synthetic interest of various research groups (8). 

Anabolic activities of testosterone, such as increases in amino acid incorporation into protein and in RNA polymerase activity, have been demonstrated in skeletal muscle. Apart from the direct anabolic effects in specific tissue, androgens antagonize the protein catabolic action of glucocorticoids. The androgen compounds with the greatest ratio of protein anabolic effects to virilizing effects are the 19-nortestosterone derivatives. Compounds that are used clinically (Table 63.3) include nandrolone phenpropionate (Durabolin), nandrolone decanoate... 

Mechanism of Action A synthetic nucleoside that inhibits influenza virus RNA polymerase activity and interferes with expression of messenger RNA. Therapeutic Effect Inhibits viral protein synthesis and replication of viral RNA and DNA. Pharmacokinetics Rapidly absorbed from the GI tract following oral administration. A small amount is systemically absorbed following inhalation. Primarily excreted in urine. Half-life 298 hr (oral) 9.5 hr (inhalation). 

Some E. coli bacteriophages, including f2, MS2, R17, and Qj8, as well as some eukaryotic viruses (including influenza and Sindbis viruses, the latter associated with a form of encephalitis) have RNA genomes. The single-stranded RNA chromosomes of these viruses, which also function as mRNAs for the synthesis of viral proteins, are replicated in the host cell by an RNA-dependent RNA polymerase (RNA replicase). All RNA viruses—with the exception of retroviruses—must encode a protein with RNA-dependent RNA polymerase activity because the host cells do not possess this enzyme. 

RNA polymerase activity is discovered in crude extracts of cells derived from an exotic fungus. The RNA polymerase initiates transcription only from a single, highly specialized promoter. As the polymerase is purified its activity declines, and the purified enzyme is completely inactive unless crude extract is added to the reaction mixture. Suggest an explanation for these observations. 

Core enzyme Four of the enzyme s peptide subunits, 2a, 1p, and 1p are responsible for the 5 ->3 RNA polymerase activity, and are referred to as the core enzyme (Figure 30.6). However, this enzyme lacks specificity, that is, it cannot recognize the promoter region on the DNA template. 

It was found that 1 acted as an antimitotic agent, not binding to tubulin, but by disorganizing the microtubule network in some fashion. In addition, it is a DNA minor groove guanine-specific alkylating agent [1]. The Et s showed potent inhibition of DNA and RNA synthesis and of RNA polymerase activity, but its inhibition of DNA polymerase activity is much less marked [75]. The potent activity of Et s was attributed, at least in part, to the unit C since the related saframycin A lacks this unit and has lower efficacy than Et 729 in comparable tumor models [74, 75]. More recent structural information on Et 743-DNA adduct was obtained by NMR spectroscopy [78]. An enantioselective total synthesis of Et 743 has been achieved by Corey et al. [79]. 

Nuclear extracts can be fractionated by chromatography on DEAE-cellulose to give three peaks of RNA polymerase activity (the use of column chromatography is explained in chapter 6). These three peaks correspond to three different RNA polymerases (I, II, and III), which differ in relative amount, cellular location, type of RNA synthesized, subunit structure, response to salt and divalent cation concentrations, and sensitivity to the mushroom-derived toxin a-amanitin. The three polymerases and some of their properties are summarized in table 28.4. 

ATP is converted to dinucleotide in magnesium-containing buffer without proteinoid in a yield of 0.7 %, but in the presence of basic proteinoid solution, acidic proteinoid microspheres, or acidic-basic proteinoid microspheres, the conversion to oligonucleotides is 2.2-2.3 %. With AMP instead of ATP no oligonucleotides result. The proteinoids are thus a model for proto-RNA polymerase activity, and ATP is reaffirmed as the source of energy for the synthesis of phosphodiester linkages 47). The microspheres of acidic proteinoid or of acidic-basic proteinoid synthesize di- and trinucleotides, while without proteinoid or basic proteinoid solution dinucleotide only results. Furthermore, the ratios of trinucleotides/dinucleotide are 0.5 for acidic-basic proteinoid microspheres, 0.2 for acidic proteinoid microspheres 47). 

Davidse, L.C., Hofman, A.E., Velthuis, G.C.M. 1983. Specific interference of metalaxyl with endogenous RNA polymerase activity in isolated nuclei of Phytophthora megasperma f.sp.medicaginis. Exp. Mycol. 344-361. 

Dzhokhadze, D. I. Goglidze, R. I. Comparative effect of gibberellic acid on RNA polymerase activity of cell nuclei in leaves and roots of pea. Fiziol. Rast., 1977, 24(4), 746-750. 

Bex, J. H. M. Effects of abscisic acid on the soluble RNA polymerase activity in maize of coleoptiles. Planta, 1972,... 

A high-throughput assay for bacterial RNA polymerase has been successfully developed and validated using a 96-well, automated format [70], The reaction mixture contained a DNA template, nucleotide substrates (NTPs), supplemented with a-33P-labeled CTP in Tris-acetate buffer (pH 6.8). The polymerase reaction was carried out at 34°C for 40 min (providing linear kinetics). The effect of dimethylsulfoxide (DMSO), the usual solvent for test compounds used in a screen, was taken into consideration. The radiolabeled RNA transcripts were allowed to bind diethyl aminoethyl (DEAE) beads, which were then separated via filtration, and radioactivity associated with the wells was quantitated to measure the RNA polymerase activity. The standard deviation of the measured activity was typically < 15% of the average. Use of this assay to screen for RNA polymerase inhibitors from chemical libraries and natural products led to the identification of DNA intercalators (known to inhibit RNA polymerase activity), rifampicin (a known inhibitors of RNA polymerase), and several derivatives of rifampicin from Actinomycetes extracts. Therefore this assay can be reliably utilized to detect novel inhibitors of bacterial RNA polymerase. 

Lineweaver-Burk plot of the kinetic data obtained by measuring the RNA polymerase activity at various concentrations of template (Fig, 5). Figure 5 depicts the... 

Figure 28.2. RNA Polymerase Active Site. A model of the transition state for phosphodiester-bond formation in the active site of RNA polymerase. The 3 -hydroxyl group of the growing RNA chain attacks the a -phosphate of the incoming nucleoside triphosphate. This transition state is structurally similar to that in DNA polymerase (see Figure 27.12).

Xia et have developed an activity-based selection method to evolve DNA polymerases with RNA polymerase activity. Stoffel fragment (SF) of Thermus aquaticus DNA polymerase is displayed on a filamentous phage by fusing it to a coat protein, and the substrate DNA template/primer duplexes are attached to other adjacent coat proteins. Phage particles displaying SF polymerases, which extend the attached primer by incorporating ribonucleoside triphosphates and biotinylated UTP, are immobilized on streptavidin-coated beads. After four rounds of screening a SF library, three mutants were isolated and shown to incorporate ribonucleoside triphosphates virtually as efficiently as the wild-type enzyme incorporates dNTP substrates. 

Anabolic steroids decrease catabolism and increase skeletal muscle protein synthesis. Whether this results in muscular hypertrophy or hyperplasia, or a combination of these, is unclear and probably depends upon the muscle studied. Different muscle types contain different cytosolic receptor numbers and, therefore, the response to anabolic steroids varies. Anabolic steroids initiate an increase in RNA polymerase activity and the synthesis of either structural or contractile proteins. In some muscles, anabolic steroids may increase the ratio of fast twitch to slow twitch fibers (Nimmo et al 1982, Snow et al 1982). Increased activity of enzymes involved in energy metabolism may also occur. However, the total glycogen content may remain unchanged (Hyyppa et al 1997). The effects are most profound in females and castrated males (Snow 1993). 

Factors, such as o-, affect RNA polymerase activity. These factors bind to the core RNA polymerase and increase its ability to bind to specific promoters. 

Shah GM, Bhattacharya RK. 1989. Alteration in hepatic nuclear RNA polymerase activity following benzo[a]pyrene administration in rat. In Vivo 3(2) 125-127. 

---