Purification and some properties of a soluble DNA-dependent RNA polymerase from nuclei of human placenta

Affinity Chromatographic Method for Determining Drug-Protein Interaction with Enhanced Speed Than Typical Frontal Analysis

Revealing drug-protein interaction is highly important to select a drug candidate with improved drug-like properties in the early stages of drug discovery. This highlights the urgent need to develop assays that enable the analysis of drug-protein interaction with high speed. Herein, this purpose was realized by the development of an affinity chromatographic method with a two-fold higher speed than typical assays like frontal analysis and zonal elution. The method involved synthesis of a stationary phase by immobilizing poly(ADP-ribose) polymerase-1 (PARP1) onto macroporous silica gel through a one-step bioorthogonal reaction, characterization of mutual displacement interaction of two canonical drugs to the immobilized PARP1, determination of the interaction between three (iniparib, rucaparib, and olaparib) drugs and the protein, and validation of these parameters by typical frontal analysis. The numbers of binding sites on the column were (2.85 ± 0.05) × 10-7, (1.89 ± 0.71) × 10-6, and (1.49 ± 0.06) × 10-7 M for iniparib, rucaparib, and olaparib, respectively. On these sites, the association constants of the three drugs to the protein were (9.85 ± 0.56) × 104, (2.85 ± 0.34) × 104, and (1.07 ± 0.35) × 105 M-1. The determined parameters presented a good agreement with the calculation by typical frontal analyses, which indicated that the current continuous competitive frontal analysis method was reliable for determining drug-protein interaction. Application of the methods was achieved by screening tubeimosides I and II as the bioactive compounds against breast cancer in Bolbostemma paniculatum. Their mechanism may be the interference of DNA repair via down-regulating PARP1 and meiotic recombination 11 expressions, thus leading to oncogene mutations and death of cancer cells. The method was high speed since it allowed simultaneous determination of binding parameters between two drugs and a protein with a smaller number of experiments to be performed. Such a feature made the method an attractive alternative for high-speed analysis of drug-protein interaction or the other bindings in a binary system.

Characterization of RNA polymerase type II from human term placenta

RNA polymerase type II from human term placenta has been isolated and characterized with respect to its template, ammonium sulfate, divalent cation, and buffer preferences. In addition, the apparent Michaelis constants for AMP and UMP incorporation have been determined. The enzyme was also analyzed by native and denaturing polyacrylamide gel electrophoresis, and evidence is presented that a single polypeptide is radiolabeled with azido purine nucleoside triphosphate photoprobes.

Low-speed purification of human placental nuclei

A simple method for the purification of human placental nuclei is described. Nuclei were isolated by homogenizing tissue in standard saline citrate solution in the presence of zinc chloride to stabilize the nuclear membranes, NP40 as non-ionic detergent and sodium bisulphite for inhibition of proteolytic activity. Nuclei purification was achieved by low-speed centrifugation through a discontinuous sucrose gradient. The purified nuclei were evaluated by morphological criteria using phase contrast and electron microscopy. The extent of contamination by cytoplasmic debris was estimated by Papanicolaou's staining technique. Biochemical criteria include measurements of alkaline phosphatase activity as a plasma membrane enzyme marker and DNA-dependent RNA polymerase activity for the functional integrity of nuclear components. Transcriptionally active nuclei were obtained but the yield of nuclei was low; however, this low yield is compensated by the high degree of purity, the simplicity of the method and the functional and morphological integrity of the purified nuclei.

[Free and template-bound RNA polymerase in normal and leukaemic human lymphocytes (author's transl)]

Specific activities are determined of two functional fractions of alpha-amanitin sensitive DNA-dependent RNA polymerases in nucleic from human normal and chronic lymphocytic leukemia lymphocytes. Specific activity of "free" RNA polymerase in CLL corresponds ot 0.133 pmoles (3H)-UMP/10(6) cells as compared to 0.209 in normals. Activities of the "engaged" enzymes are 0.139 in CLL and 0.132 in normals. "Free" enzymes in NL and CLL are completely inhibited by 400 ng/ml Rifamycin AF/013, while the "engaged" enzymes exhibit 70% of their original activity. 1.0 ng/ml alpha-amanitin suppress 50% of the activity of the "free" enzyme in CLL. The "free" enzyme in NL and the "engaged" enzymes in NL and CLL do not show any residual activity in the presence of 1.0 ng/ml alpha-amanitin.

Hormonal control of transcription in higher plants

1. Nucleolar RNA polymerase Ib obtained from auxin-treated lentil roots exhibits a higher transcriptional activity than the enzyme obtained from control roots. This difference is due to a change in the enzyme properties after auxin treatment. It is suggested that the hormonal effect is mediated by a factor that changes the molecular properties of nucleolar RNA polymerase. 2. Four fractions, alpha, beta, gamma and delta, that stimulate the activity of RNA polymerase Ib, have been extracted from lentil roots. Two of them, gamma and delta have been studied. Factor delta can stimulate nucleolar polymerase Ib and the nucleoplasmic enzyme II equally well, while factor gamma is specific for polymerase Ib. 3. The curve of UMP incorporation in vitro, with and without factors gamma or delta suggests that they are initiation factors. This conclusion is reinforced by the analysis of simultaneous incorporation of [gamma-32P]ATP and [3H]UMP in the RNAs synthesized in vitro. 4. Although the level of factor delta is independent of auxin treatment, that of factor gamma is doubled in auxin-treated roots. These results suggest that factor gamma is an auxin-induced protein that modulates the specific activity of the nucleolar RNA polymerase. 5. A general model of the mode of action of auxins at the molecular level is proposed. It integrates into a unified scheme the above results as well as those obtained by other workers.

Changes in chick brain RNA polymerase associated with an imprinting procedure

The specific activity of RNA polymerase was measured in nuclei from 3 brain regions of 1-day-old chicks which had been exposed for different periods to either an imprinting stimulus or diffuse light and compared to that in birds kept in the dark. Several differences were observed, all of which were short-lived. After 15 min treatment there was a decrease in enzyme activity in the forebrain base of both stimulus- and diffuse light-exposed birds as compared to dark birds, which disappeared by 30 min treatment. After 30 min treatment there was increased activity of the enzyme in the forebrain roof of the stimulus-exposed as compared to both diffuse light-exposed and dark-maintained birds. There were no differences in activity in any region from 45 min up to 120 min of treatment. These changes in RNA polymerase activity were in general accord with the altered uracil incorporation into RNA measured in previous experiments where birds were exposed to 38 or 76 min of treatment, and also with our earlier report on RNA polymerase activity after 30 min treatment.

[DNA-dependent RNA polymerases in human leukocytes. II different specific activities of the polymerases A and B in acute and chronic leukemia and their prognostic relevance (author's transl)]

Specific Activities of DNA-dependent RNA polymerases A and B have been determined in nuclei from leukocytes in acute and chronic leukemia. Enzyme activities, dependent on exogenous DNA template, were determined in homogenates of nuclei from isolated mononuclear cells or from isolated granulocytes. Activities of polymerases A and B have been found significantly elevated in homogenates of nuclei from mononuclear cells in acute myelocytic leukemia, while they were found subnormal in corresponding cell fractions from chronic myelocytic leukemia and chronic lymphatic leukemia. During cytostatic treatment polymerase activities were approaching normal values. The prognostic relevance of these data for the course of human leukemia is discussed.

Protein synthesis in the liver of rats injected with cholesteryl 14-methylhexadecanoate

1. Rats were injected intraperitoneally with cholesteryl 14-methylhexadecanoate and killed after various intervals of time up to 3 days; ribosomes and cell sap were isolated from their liver tissue. These fractions were tested for their ability to participate in protein synthesis. 2. Protein synthesis in complete systems containing ribosomes, cell sap and all necessary cofactors was significantly enhanced at 12 and 72h after the injection and significantly inhibited at 24h. At early times after injection isolated ribosomes had a slightly enhanced ability to bind nRNA. Peptide-elongation processes (i.e. binding of aminoacyl-tRNA to ribosomes, peptidyl transfer and polyphenylalanine synthesis) showed significant stimulation or inhibition depending on the time after injection of the ester. 3. A correlation was found between the ability of cell sap to stimulate polyphenylalanine synthesis and the relative cholesteryl 14-methylhexadecanoate content in the postmicrosomal supernatant at different time-intervals after administration of the ester. No significant changes were found in its content in the whole liver tissue. 4. Since the injected ester has previously been shown to accumulate in some enzymic fractions, the changes in its relative content may represent a regulatory mechanism modulating the rate of protein synthesis.

Reinitiation of RNA synthesis on transcription of chromatin DNA by Escherichia coli RNA polymerase

The transcription of DNA in chromatin by Escherichia coli RNA polymerase resembles that of isolated DNA in two important respects: the release of nascent RNA and reinitiation of RNA synthesis is dependent on the salt concentration, and RNA synthesis is markedly stimulated by the addition of ribosomes.

Solubilized DNA-dependent RNA polymerase from human placenta: A Mn(2+)-dependent enzyme

The 100-fold purified RNA polymerase activity from human placenta is completely dependent upon added DNA. The enzyme is most active at 3 mM Mn(2+) in the presence of 100 mM (NH(4))(2)SO(4). Denatured DNA is a better template than native DNA. alpha-Amanitin completely inhibits the incorporation of 3H-UMP, while rifampicin has no influence upon the enzymatic activity.