Effects of genistein on growth and development of aquatic vertebrates.
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Animals↗
Biomedical subjects
C R Toth
Publications and source records attributed to C R Toth.
alpha5 subunit in Trypanosoma brucei proteasome can self-assemble to form a cylinder of four stacked heptamer rings.
The proteasomes have a central role in catalysing protein degradation among both prokaryotes and eukaryotes. The 20 S proteasome constitutes their catalytic core. In studying the structure of Trypanosoma brucei 20 S proteasomes, we isolated by two-dimensional (2D) gel electrophoresis a 27 kDa subunit protein with an estimated pI of 4.7 and subjected it to mass spectrometric analysis. A tryptic peptide sequence from the protein was found identical with that of the rat alpha5 subunit. With the use of antiserum against T. brucei 20 S proteasomes to screen a T. b. rhodesiense lambda expression cDNA library, we obtained a cDNA clone encoding a full-length protein of 246 amino acid residues with a calculated molecular mass of 27174 Da and a pI of 4.71. It bears 50. 0% and 46.3% sequence identity with rat and yeast proteasome subunit alpha5 respectively, and matches all the peptide sequences derived from MS of the 2D gel-purified protein. The protein is thus designated the alpha5 subunit of T. brucei 20 S proteasome (TbPSA5). The recombinant protein, expressed in plasmid-transformed Escherichia coli, was found in a 27 kDa monomer form as well as polymerized forms with estimated molecular masses ranging from 190 to 800 kDa. Under the electron microscope, the most highly polymerized forms bear the appearance of cylinders of four-stacked heptamer rings with an estimated outer diameter of 14.5 nm and a length of 18 nm, which were immunoprecipitable by anti-(T. brucei 20 S proteasome) antiserum. In view of the documented self-assembly of the archaeon proteasome alpha subunit into double heptamer rings and the spontaneous assembly of the two alpha subunits from the 20 S proteasome of Rhodococcus erythropolis, the self-assembly of the T. brucei alpha subunit might reflect a common feature of proteasome biogenesis shared by prokaryotes and primitive eukaryotes such as the trypanosomes but apparently lost among the higher forms of eukaryote such as the yeast and the mammals.
Amino Acid Sequence↗
Binding and cooperative interactions between two B cell-specific transcriptional coactivators.
The class II transactivator (CIITA) and B cell octamer-binding protein 1/octamer-binding factor 1/Oct coactivator from B cells (Bob1/OBF-1/OCA-B) represent two B cell-specific transcriptional coactivators. CIITA and Bob1 interact with proteins that bind to conserved upstream sequences in promoters of class II major histocompatibility genes and octamer-binding transcription factors Oct-1 and Oct-2, respectively. Both CIITA and Bob1 increase the expression from the DRA promoter, which is a prototypic class II promoter. Moreover, in the presence of CIITA, interactions between class II promoters and Bob1 are independent of the octamer-binding site. Using in vivo and in vitro binding assays, we confirm that Bob1 binds to CIITA. Thus, CIITA not only activates the expression of class II genes but recruits another B cell-specific coactivator to increase transcriptional activity of class II promoters in B cells.
B-Lymphocytes↗
Members of the nuclear factor kappa B family transactivate the murine c-myb gene.
Expression of the c-myb proto-oncogene is primarily detected in normal tissue and tumor cell lines of immature hematopoietic origin, and the down-regulation of c-myb expression is associated with hematopoietic maturation. Cell lines that represent mature, differentiated hematopoietic cell types contain 10-100-fold less c-myb mRNA than immature hematopoietic cell types. Differences in steady-state c-myb mRNA levels appear to be primarily maintained by a conditional block to transcription elongation that occurs in the first intron of the gene. The block to transcription elongation has been mapped, using nuclear run-on analysis, to a region of DNA sequence that is highly conserved between mouse and man. Two sets of DNA-protein interactions, flanking the site of the block to transcription elongation, were detected that exhibited DNA-binding activities that strongly correlated with low steady-state c-myb mRNA levels. Several criteria demonstrated that members of the nuclear factor kappa B (NF-kappa B) family of transcription factors were involved in the DNA-protein interactions identified in these two sets. Surprisingly, cotransfection experiments demonstrated that coexpression of members of the NF-kappa B family, specifically p50 with p65 and p65 with c-Rel, transactivated a c-myb/chloramphenicol acetyltransferase reporter construct that contained 5'-flanking sequences, exon I, intron I, and exon II of the c-myb gene. Transactivation by these heterodimer combinations was dependent on regions of the c-myb first intron containing the NF-kappa B-binding sites. These findings suggest that NF-kappa B family members may be involved in either modifying the efficiency of transcription attenuation or acting as an enhancer-like activity to increase transcription initiation. Thus, the regulation of c-myb transcription may be quite complex, and members of the NF-kappa B family likely play an important role in this regulation.
Animals↗
Cation-dependence of the self-association behavior of guanylyl-(3'-5')-guanosine.
The aggregation behavior of guanylyl-(3'-5')-guanosine, GpG, in the form of the tetramethylammonium (TMA), Li, Na, and K salts in aqueous solution has been investigated by NMR and FTIR techniques. The salts were prepared by a cation-exchange method. The ability of the cations to induce aggregate formation is TMA+ < Li+ < Na+ < K+, where TMA+ has only a weakly promoting action and K+ has a very strong effect. Three types of aggregates have been observed: (a) small aggregates which are in rapid exchange with respect to the NMR time scale; (b) intermediate-sized aggregates which are slow to exchange; (c) very large aggregates which can only be observed by FTIR. In all cases the aggregated species are held together by base stacking and guanine-guanine hydrogen bonding. A stoichiometry of 2 GpG per K+ has been determined by a 1H NMR titration of TMAGpG with KCl. Models have been proposed for the various-sized species. These include stacked dimers, stacked tetramers (similar to G-tetrads), and species in which K+ ion bridges between phosphates in separate tetramers.
Cations, Monovalent↗
Constitutive and cell cycle regulated expression of c-myc mRNA is related to the state of differentiation in murine B-lymphoid tumors.
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Animals↗
The preparation and spectroscopic characterization of a weakly self-associating salt of guanylyl-(3'-5')-guanosine.
The tetramethylammonium salt of guanylyl-(3'-5')-guanosine has been prepared by a cation-exchange technique and it has been found that the tetramethylammonium ion drastically reduces the self-association of GpG in solution. This has allowed the characterization of GpG by FTIR and 1-D and 2-D NMR spectroscopy. A complete, well-resolved 1H NMR spectrum in D2O has been obtained and all resonances have been assigned. A weak, essentially non-cooperative intermolecular association is observed in solution (15-20 mM) below 40 degrees C. The association occurs via base stacking and base-base hydrogen bonding.
Chemical Phenomena↗