Identification of a chemical inhibitor for nuclear speckle formation: implications for the function of nuclear speckles in regulation of alternative pre-mRNA splicing.

Nuclear speckles are subnuclear structures enriched with RNA processing factors and poly (A)(+) RNAs comprising mRNAs and poly (A)(+) non-coding RNAs (ncRNAs). Nuclear speckles are thought to be involved in post-transcriptional regulation of gene expression, such as pre-mRNA splicing. By screening 3585 culture extracts of actinomycetes with in situ hybridization using an oligo dT probe, we identified tubercidin, an analogue of adenosine, as an inhibitor of speckle formation, which induces the delocalization of poly (A)(+) RNA and dispersion of splicing factor SRSF1/SF2 from nuclear speckles in HeLa cells. Treatment with tubercidin also decreased steady-state MALAT1 long ncRNA, thought to be involved in the retention of SRSF1/SF2 in nuclear speckles. In addition, we found that tubercidin treatment promoted exon skipping in the alternative splicing of Clk1 pre-mRNA. These results suggest that nuclear speckles play a role in modulating the concentration of splicing factors in the nucleoplasm to regulate alternative pre-mRNA splicing.

Quality and safety issues related to traditional animal medicine: role of taurine.

BACKGROUND: Calculus Bovis (:C.Bovis) is one of the most precious and commonly-used medicinal materials in Japan and China. As the natural occurrence is very rare, a source of supply for C. Bovis is far behind the actual need and great efforts have been taken for some substitutes of natural C. Bovis. Unfortunately, very little information is available on the quality and/or clinical efficacy of medication based on C. Bovis. To ensure sustainable use of traditional therapeutic agents derived from C. Bovis, we felt that several issues needed to be addressed: 1) the source of the C. Bovis materials and quality control; 2) the role of taurine in the efficacy of C. Bovis. METHODS: Nine samples of natural C. Bovis and its substitutes were collected. ICP-MS was used for elemental analysis and the characterization was performed by principal component analysis (PCA) and soft independent modeling of class analogy (SIMCA) as multivariate approaches. The efficacy of C. Bovis was evaluated for morphology, viability and beating pattern on cultured cardiac myocytes and/or fibroblasts. RESULTS: PCA and multi-elemental focus was effective in discriminating C. Bovis samples derived from different habitats. A satisfactory classification using SIMCA was obtained among Australia C. Bovis, other habitats and the substitutes. Australian samples had better batch uniformity than other habitats and were composed of fewer elements. We have used Australian C. Bovis for assessment on its bioactive compounds. Rat cardiac cells incubated with C. Bovis extract (0.01-0.1 mg/ml) maintained normal morphology, viability and beating pattern. Cardiac myocytes and fibroblasts treated for 48 h with CA (0.5 mM) or DCA (0.1 mM) caused cell injury, as reflected by changes in appearance and a reduction of viability detected by the MTS assay. In cardiomyocytes, 0.5 h exposure of CA (0.5 mM) markedly decreased the velocity ratio of beating, whereas the simultaneous addition of 1 mM taurine largely prevented the decrease. CONCLUSIONS: The multi-elemental focus provided some references for the quality control and the efficacy of C. Bovis. Taurine partly attenuated the harmful actions of bile acids. It is plausible that the relationship between taurine and the bile acids contributes to therapeutic effect of C. Bovis.

Tool from traditional medicines is useful for health-medication: Bezoar Bovis and taurine.

Bezoar Bovis (BB:dried cattle gallbladder stones) has been used empirically in Asia for over 3000 years to treat heart and liver disorders. Yet its therapeutic potential remains unexplored by Western researchers. The aim of this study has been to clarify the actions of BB on cultured cardiomyocytes and to identify its active component(s). BB is a component of 98.7% of the Japanese over the counter (OTC) cardioactive drugs. The water-extract of BB exhibits protection action against arrhythmias produced by low Ca2+ and high Ca2+ in the medium. On the other hand, the Ca(2+)-antagonist, verapamil, did not suppress arrhythmias that developed in cell culture. Rather, it aggravated the beating status of the cardiomyocytes. The major constituents of the BB extract are bile salts (cholate, deoxycholate, taurocholate) and amino acids (taurine, cysteine, leucine, isoleucine). Most cells incubated with bile salts developed morphological damage. However, one of the major constituents of the BB extract, taurine, was effective in protecting against the abnormal beating pattern induced by high Ca2+. Since beta-alanine, an inhibitor of taurine transport, antagonized the protective effects of both BB and taurine, it is likely that the effect of BB is partly mediated by taurine.

Robust stimulation of TrkB induces delayed increases in BDNF and Arc mRNA expressions in cultured rat cortical neurons via distinct mechanisms.

In cultures of rat cortical neurons, we found that stimulation of tyrosine receptor kinase B (TrkB) with brain-derived neurotrophic factor (BDNF) induced a biphasic expression of BDNF exon IV-IX mRNA, which became obvious 1-3 h (primary induction) and 24-72 h (delayed induction) after the stimulation, and characterized the delayed induction in relation to the mRNA expression of activity-regulated cytoskeleton-associated protein (Arc). Withdrawal of BDNF from the medium after stimulation for 3 h allowed the delayed induction, which was caused at the transcriptional level and dependent upon the initial contact between exogenously added BDNF and TrkB, the effect of which was time- and dose-dependent. The primary induction was controlled by the extracellular signal-regulated kinase/mitogen-activated protein kinase (ERK/MAPK) whereas the secondary induction by the calcium (Ca(2+)) signaling pathway. The enhanced Arc or Zif268 mRNA expression was controlled by activation of the ERK/MAPK pathway, both of which were repressed by blocking the binding of endogenously synthesized BDNF to TrkB. Thus, robust stimulation of TrkB autonomously induces delayed BDNF mRNA expression in an activity-dependent manner in rat cortical neurons, resulting in the stimulation of Arc mRNA expression through endogenously synthesized BDNF, the process being orchestrated by the Ca(2+) and ERK/MAPK signaling pathways.