Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.26.9 (ribonuclease)
 6,589 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Ferritin synthesis is regulated at the translational level by iron, but it is likely that transcriptional regulation of H and L genes is responsible for tissue-specific distribution of H and L mRNAs. In order to define the regions important for transcriptional regulation of the mouse ferritin H gene, we have linked the promoter, including the transcription start site, and 5 kilobases of upstream sequence to a reporter gene (human growth hormone). This construct and a series of 5' deletion mutants have been used to transfect erythroid (K562, mouse erythroleukemia (MEL)) and hepatoma (HepG2) cell lines. Measurement of growth hormone in the culture medium and analysis of ferritin-growth hormone transcripts by a ribonuclease protection assay revealed that a 140-base pair minimal promoter is sufficient to confer a high level of expression to the reporter gene in both cell types. In addition, a 180-base pair fragment, lying 4.5 kilobases upstream of the ferritin transcription start site, functions like an inducible enhancer during N,N'-hexamethylene-bis-acetamide-induced differentiation of MEL cells. A perfect match to a consensus binding motif to the erythroid transcription factor NF-E2 is present in this regulatory element, but the mutant NF-E2 enhancer retains the inducible activity in stably transfected MEL cells, and the results from gel retardation assays suggest that protein-DNA complexes that form in vitro between the ferritin enhancer and MEL nuclear extracts do not contain NF-E2. Thus, nuclear factors that mediate inducibility of the ferritin enhancer remain to be identified.
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PMID:Mouse ferritin H subunit gene. Functional analysis of the promoter and identification of an upstream regulatory element active in erythroid cells. 805 Nov 21

Reaction of terbium triflate with a heptadentate ligand derivative of cyclen, L1 = 2-[7-ethyl-4,10-bis(isopropylcarbamoylmethyl)-1,4,7,10-tetraazacyclododec-1-yl]-N-isopropyl-acetamide, produced a new synthetic ribonuclease, [Tb(L1)(OTf)(OH(2))](OTf)(2).MeCN (C1). X-ray crystal structure analysis indicates that the terbium(III) center in C1 is 9-coordinate, with a capped square-antiprism geometry. While the terbium(III) center is tightly bound by the L1 ligand, two of the coordination sites are occupied by labile water and triflate ligands. In water, the triflate ligand is likely to be displaced, forming [Tb(L1)(OH(2))(2)](3+), which is able to effectively promote RNA cleavage. This complex greatly accelerates the rate of intramolecular transesterification of an activated model RNA phosphodiester, uridine-3'-p-nitrophenylphosphate (UpNP), with k(obs) = 5.5(1) x 10(-2) s(-1) at 21 degrees C and pH 7.5, corresponding to an apparent second-order rate constant of 277(5) M(-1) s(-1). By contrast, the analogous complex of an octadentate derivative of cyclen featuring only a single labile coordination site, [Tb(L2)(OH(2))](OTf)(3) (C2), where L2 = 2-[4,7,10-tris(isopropylcarbamoylmethyl)-1,4,7,10-tetraazacyclododec-1-yl]-N-isopropyl-acetamide, is inactive. [Tb(L1)(OH(2))(2)](3+) is also capable of hydrolyzing short transcripts of the HIV-1 transactivation response (TAR) element, HIV-1 dimerization initiation site (DIS) and ribosomal A-site, as well as formyl methionine tRNA (tRNA(fMet)), albeit at a considerably slower rate than UpNP transesterification (k(obs) = 2.78(8) x 10(-5) s(-1) for TAR cleavage at 37 degrees C, pH 6.5, corresponding to an apparent second-order rate constant of 0.56(2) M(-1)s(-1)). Cleavage is concentrated at the single-stranded "bulge" regions of these RNA motifs. Exploiting this selectivity, [Tb(L1)(OH(2))(2)](3+) was successfully employed in footprinting experiments, in which binding of the Tat peptide and neomycin B to the bulge region of the TAR stem-loop was confirmed.
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PMID:New macrocyclic terbium(III) complex for use in RNA footprinting experiments. 1911 12