Low-speed purification of human placental nuclei

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.

Nuclear localization and molecular partners of BIG1, a brefeldin A-inhibited guanine nucleotide-exchange protein for ADP-ribosylation factors

Brefeldin A-inhibited guanine nucleotide-exchange protein 1 (BIG1) is an approximately 200-kDa brefeldin A-inhibited guanine nucleotide-exchange protein that preferentially activates ADP-ribosylation factor 1 (ARF1) and ARF3. BIG1 was found in cytosol in a multiprotein complex with a similar ARF-activating protein, BIG2, which is also an A kinase-anchoring protein. In HepG2 cells growing with serum, BIG1 was primarily cytosolic and Golgi-associated. After incubation overnight without serum, a large fraction of endogenous BIG1 was in the nuclei. By confocal immunofluorescence microscopy, BIG1 was localized with nucleoporin p62 at the nuclear envelope (probably during nucleocytoplasmic transport) and also in nucleoli, clearly visible against the less concentrated overall matrix staining. BIG1 was also identified by Western blot analyses in purified subnuclear fractions (e.g., nucleoli and nuclear matrix). Antibodies against BIG1, nucleoporin, or nucleolin coimmunoprecipitated the other two proteins from purified nuclei. In contrast, BIG2 was not associated with nuclear BIG1. Also of note, ARF was never detected among proteins precipitated from purified nuclei by anti-BIG1 antibodies, although microscopically the two proteins do appear sometimes to be colocalized in the nucleus. These data are consistent with independent intracellular movements and actions of BIG1 and BIG2, and they are also evidence of the participation of BIG1 in both Golgi and nuclear functions.

Regulation of interleukin-1-stimulated GMCSF mRNA levels in human endothelium

The regulation of interleukin-1 (IL-1)-mediated increases in GMCSF mRNA levels in human endothelium was examined and determined to occur in a time- and protein kinase C (PKC)-dependent manner. IL-1beta induced the early activation and translocation of PKC isotypes alpha and beta2 to the nucleus and PKC inhibition attenuated the IL-1-mediated increase in GMCSF mRNA levels. PKC activation by PMA alone, in the absence of IL-1beta activation, however, was insufficient to allow GMCSF mRNA detection. Increasing cyclic adenosine nucleotide (cAMP) levels suppressed IL-1beta-induced increases in GMCSF mRNA levels. In contrast, botulinum toxin C, which mediates the ADP ribosylation of a 21 kD ras-related G protein, augmented IL-1beta-induced GMCSF mRNA expression. Inhibition of protein synthesis (with cycloheximide) raised basal GMCSF mRNA transcripts to detectable levels, augmented IL-1-induced increases in GMCSF mRNA levels, and exhibited negative regulation by cAMP. Finally, disruption of either microtubules (with colchicine) or microfilaments (with cytochalasin B) resulted in reduced GMCSF mRNA expression in response to IL-1beta. These results are compatible with a model wherein IL-1-mediated increases in human endothelial cell GMCSF mRNA may be linked to both nuclear protein kinase C activation and activation of a low molecular weight G-protein, although neither activity alone is sufficient to increase the levels of GMCSF mRNA.

Detection of benzo[a]pyrene diol epoxide-DNA adducts in human placenta

Human placenta is a readily available organ that responds to maternal environmental insult and has been previously used to investigate metabolism and bioactivation of procarcinogens, for example, benzo[a]pyrene. HPLC in combination with synchronous fluorescence spectroscopy was used to examine 28 placentas for the presence of benzo[a]pyrene diol epoxide-DNA adducts, and 10 of these were found to be positive. DNA samples from these placentas were subsequently pooled and subjected to partial enzymatic digestion to oligonucleotide fragments. Concentration of those DNA fragments containing benzo[a]pyrene diol epoxide-DNA adducts was achieved by immunoaffinity chromatography with polyclonal antibodies raised against these adducts. Column eluates were hydrolyzed under mild acid conditions and extracted with an organic solvent. The presence of benzo[a]pyrene-7,10/8,9-tetrahydrotetrol residues in the extracts was determined by HPLC and synchronous fluorescence spectroscopy and was confirmed by GC/MS. The results unequivocally confirm bioactivation and formation of DNA adducts from benzo[a]pyrene in human placenta in vivo and establish a methodological approach to direct measurement of carcinogen-DNA adducts that are formed as a result of human environmental exposure.

Analysis of chromatin proteins from human placenta

Low-salt extracts of chromatin from human term placenta have been examined for the presence of the high mobility group (HMG) proteins. Based upon salt-dissociation characteristics, solubilities in trichloroacetic acid and electrophoretic behaviour on sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and non-equilibrium pH gradient gel electrophoresis (NEPHGE), each of the HMG proteins is present, including HMG-1, -2, -E, -14, and -17. A remarkably large amount of HMG-E is present in term human placenta. Additionally, a protein not previously recognized, which we designate HMG-PL, is present in term placenta. Electrophoretic comparison of the HMG proteins from placentae of varying gestational age, using NEPHGE, demonstrates that all of the placental HMG proteins exhibit multiplicity, reminiscent of chicken erythrocyte HMG proteins. Specifically, we found HMG-E to be unaltered in amounts relative to HMG-1 and -2 in placentae varying from 20 to 40 weeks of gestation. HMG-PL, however, is differentially expressed, increasing in amounts as gestation proceeds past 34 weeks. HMG-PL was purified and subjected to amino acid analysis. Its composition supports the notion that HMG-PL is a member of the HMG-1 family.