Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.27.4 (ribonuclease)
 6,621 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Inability to culture the disease-producing amastigote form of Leishmania has greatly hampered its study. We have biochemically characterized an axenically cultured amastigote-like form of Leishmania pifanoi. This form closely resembles amastigotes in proteinase, ribonuclease, adenine deaminase and peroxidase activity. It also exhibits comparable rates of growth, transformation, synthesis of DNA, RNA and protein, and metabolism of glucose and linoleic acid. It is distinct from promastigotes in these characteristics. The expression of the genes for beta-tubulin and the P100/11E reductase is developmentally regulated in this axenic form as in amastigotes. These results, combined with previous demonstrations of amastigote morphology and antigenicity in the culture form, confirm that Leishmania amastigotes have been successfully propagated in axenic media. This strain should serve as an excellent model for the study of amastigote biochemistry, pharmacology and immunology, and the molecular genetics of the transformation between amastigote and promastigote forms.
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PMID:Biochemical and molecular characterization of Leishmania pifanoi amastigotes in continuous axenic culture. 177 52

Using an in vitro ribonuclease protection assay, it was shown that synthetic antisense transcripts from the 5'-upstream region of the beta-tubulin gene are efficiently imported into isolated Leishmania mitochondria. Import occurred after a lag of about 30 min at 25 degrees C and was dependent on ATP. Preincubation experiments suggested that import consists of a slow interaction of mitochondria with RNA, followed by rapid ATP-dependent uptake. Import was saturable with antisense RNA at about 1 nM concentration, and sequence-specific, as shown by lack of import of other labelled transcripts. Deletion analysis demonstrated a correlation between efficiency of import and the number of oligopurine motifs on the antisense RNA. Several small ribosomal RNAs (srRNAs) and Leishmania tRNA competed with antisense RNA for import. Incubation of mitochondria with srRNAs and tRNA in the presence of radiolabelled UTP resulted in the ribonuclease-resistant labelling of these RNAs by the mitochondrial terminal uridylyl transferase. Extracts of isolated mitochondria contain a factor binding to antisense RNA, as shown by gel retardation assay. These observations indicate the presence of a receptor-mediated import pathway for srRNAs and tRNA in Leishmania mitochondria.
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PMID:Import of small RNAs into Leishmania mitochondria in vitro. 807 74

A Chinese hamster alpha-tubulin cDNA was modified to encode an 11-amino acid carboxyl-terminal extension containing the immunodominant epitope from influenza hemagglutinin antigen (to create HA alpha 1-tubulin) and was cloned into a vector for expression in mammalian cells. 12 stable CHO cell lines expressing this HA alpha 1-tubulin were isolated and characterized. HA alpha 1-tubulin incorporated into all classes of microtubules, assembled to the same extent as the endogenous tubulin, and did not perturb the growth of the cells in which it was expressed. However, overexpression of HA alpha 1-tubulin strongly repressed the synthesis of endogenous alpha-tubulin while having little or no effect on the synthesis of beta-tubulin. Treatment of transfected cells with sodium butyrate to induce even greater expression of HA alpha 1-tubulin led to a further decrease in synthesis of endogenous alpha-tubulin that was fully reversible upon removal of the inducer. Decreased synthesis of alpha-tubulin in transfected cells did not result from decreased levels of alpha-tubulin mRNA, as demonstrated by ribonuclease protection assays. On the other hand, colchicine, a drug previously shown to destabilize the tubulin message, caused a clear reduction in both protein synthesis and mRNA levels for transfected HA alpha 1-tubulin and endogenous alpha-tubulin, thus indicating that the decreased alpha-tubulin synthesis observed as a result of HA alpha 1-tubulin overexpression is distinct from the previously described autoregulation of tubulin. The results are consistent with a mechanism in which free alpha-tubulin inhibits the translation of its own message as a way of ensuring stoichiometric synthesis of alpha- and beta-tubulin.
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PMID:alpha-Tubulin limits its own synthesis: evidence for a mechanism involving translational repression. 897 20

The structure of isotype-specific regions of classes 1, II, III, IVa and IVb of canine beta-tubulin was characterized by 3'-RACE and the expression of these isotypes in canine tissues was examined by ribonuclease protection assay (RPA). Furthermore, a malignant mammary tumor-derived osteosarcoma-like cell line was established and the altered expression of beta-tubulin isotypes in taxol-resistant sublines was analyzed. The deduced amino acid sequences in isotype-specific regions corresponding to classes I, II and IVb were identical to those of humans and mice, but those in classes III and IVa showed slight differences among species. RPA revealed that classes I and IVb were widely distributed, but classes II, III and IVa were restricted to the brain. Because RPA could clearly distinguish the expression of class IVa from that of class IVb, it was thought to be more useful than northern blot for analysis of beta-tubulin isotype expression. In vitro, taxol-resistant sublines displayed a significant increase in class IVa as compared with taxol-sensitive cells, suggesting that altered expression of class IVa was associated with taxol resistance in these cell lines.
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PMID:Characterization of isotype-specific regions of five classes of canine beta-tubulin and their expression in several tissues and cell culture. 1178 7

Estradiol has been shown to act in the central nervous system to promote neuronal growth, differentiation, and synaptic plasticity. Recent evidence indicates that estrogens exert these effects by enhancing the expression of genes that encode key proteins of the neuronal cytoskeleton and synaptic membranes. In a previous report, we demonstrated a sex-related difference in the developmental expression of Class II beta-tubulin (RBT(1)) mRNA, which encodes a neural-specific tubulin isotype. This difference, not shared by Class IV beta-tubulin mRNA or the mRNAs encoding neurofilament proteins, was restricted to the hypothalamus. RBT(1) mRNA levels were found to decrease in both sexes during postnatal development, but significantly earlier in females than in males, suggesting that the difference is steroid-dependent. The present experiments demonstrate that 17beta-estradiol increases, in a stereospecific manner, RBT(1) mRNA levels in the hypothalamus of developing female rats. The effect was also region-specific, us it was not detected in either the cerebral cortex or the cerebellum. The increase in RBT(1) mRNA levels was observed after either in vivo administration of 17beta-estradiol or in vitro exposure of the hypothalamus to the steroid, and it was evident during both neonatal-infantile development (4 to 12 days of age) and near the time of puberty (29 days of age). The effect was detected by RNA blot hybridization and verified by a sensitive, sequence-specific ribonuclease (RNase) protection assay. In vitro exposure of hypothalamic fragments containing the arcuate/ventromedial nucleus-median eminence region of 28-day-old animals to 17beta-estradiol prevented the decline in RBT(1) mRNA levels that follows selective blockade of mRNA synthesis via pharmacological inhibition of RNA polymerase II. The results suggest that the neurotrophic effects exerted by 17beta-estradiol during early postnatal development of the hypothalamus and in the arcuate/ventromedial nuclei at the time of puberty are, at least in part, mediated by an increase in RBT(1) mRNA levels, the consequence of an estradiol-dependent increase in RBT(1) mRNA stability.
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PMID:Estradiol Increases Neural-Specific Class II-beta-Tubulin mRNA Levels in the Developing Female Hypothalamus by Regulating mRNA Stability. 1991 49