Differential expression of RNA exosome subunits in the amphibian Lithobates catesbeianus during reproductive and non-reproductive periods.

OBJECTIVE: The RNA exosome is an evolutionarily conserved 3'-5' exoribonucleolytic protein complex involved in processing and degradation of different classes of nuclear and cytoplasmic RNAs, and, therefore, important for the posttranscriptional control of gene expression. Despite the extensive in vivo functional studies and the structural data on the RNA exosome, few studies have been performed on the localization and expression of exosome subunits during gametogenesis, process during which gene expression is largely controlled at the posttranscriptional level. RESULTS: We report the identification of exosome subunits in Lithobates catesbeianus and analysis of the differential subcellular localization of RNA exosome core and catalytic subunits in testis cells. In addition, we show seasonal differences in the expression levels of four exosome subunits in different organs. In addition to being part of the RNA exosome complex, its subunits might participate independently of the complex in the control of gene expression during seasonal variation in bullfrog tissues. These results may be relevant for other eukaryotic species.

Effects of nemorosone, isolated from the plant Clusia rosea, on the cell cycle and gene expression in MCF-7 BUS breast cancer cell lines.

BACKGROUND: Breast cancer is the cause of considerable morbidity and mortality in women. While estrogen receptor antagonists have been widely used in breast cancer treatment, patients have increasingly shown resistance to these agents and the identification of novel targeted therapies is therefore required. Nemorosone is the major constituent of the floral resin from Clusia rosea and belongs to the class of polycyclic polyisoprenylated benzophenones of the acylphloroglucinol group. The cytotoxicity of nemorosone in human cancer cell lines has been reported in recent years and has been related to estrogen receptors in breast cancer cells. METHODS: Changes induced by nemorosone in the cell cycle and gene expression of the MCF-7 BUS (estrogen-dependent) breast cancer cell line were analyzed using flow cytometry and the RT(2) Profiler PCR array, respectively. RESULTS: In comparison to breast cancer cells without treatment, nemorosone induced discrete cell cycle arrest in the G1 phase and significant depletion in the G2 phase. Moreover, the compound altered the expression of 19 genes related to different pathways, especially the cell cycle, apoptosis and hormone receptors. CONCLUSION: These promising results justify further studies to clarify mechanisms of action of nemorosone, in view of evaluate the possible use of this benzophenone as adjuvant in the treatment of breast cancer.