Coronavirus nucleocapsid protein is abundant in infected cells and participates in viral RNA replication and transcription. The central domain of the nucleocapsid protein contains several arginine/serine (RS) dipeptides, the biological significance of which has not been well investigated. In the present study, we demonstrate that the severe acute respiratory syndrome coronavirus nucleocapsid protein is phosphorylated primarily within the RS‐rich region in cells and by SR protein kinase 1 in vitro. The nucleocapsid protein could suppress translation and its RS motif is essential for such an activity. Moreover, phosphorylation of the RS motif could modulate the translation inhibitory activity of the nucleocapsid protein. We further found that RS motif phosphorylation did not significantly affect RNA binding of the nucleocapsid protein but impaired its multimerization ability. We observed that the nucleocapsid protein could translocate to cytoplasmic stress granules in response to cellular stress. Deletion or mutations of the RS motif enhanced stress granule localization of the nucleocapsid protein, whereas overexpression of SR protein kinase 1 inhibited nucleocapsid protein localization to stress granules. The nucleocapsid protein lacking the RS motif formed high‐order RNP complexes, which may also account for its enhanced stress granule localization. Taken together, phosphorylation of the severe acute respiratory syndrome‐CoV nucleocapsid protein modulates its activity in translation control and also interferes with its oligomerization and aggregation in stress granules.

BackgroundFlavones found in plants display various biological activities, including anti-allergic, anti-viral, anti-inflammatory, anti-oxidation, and anti-tumor effects. In this study, we investigated the anti-tumor effects of flavone, apigenin and luteolin on human breast cancer cells.MethodsThe anti-cancer activity of flavone, apigenin and luteolin was investigated using the MTS assay. Apoptosis was analyzed by Hoechst 33342 staining, flow cytometry and western blot. Cell migration was determined using the culture inserts and xCELLigence real-time cell analyzer instrument equipped with a CIM-plate 16. Real-time quantitative PCR and western blot were used to determine the signaling pathway elicited by flavone, apigenin and luteolin.ResultsFlavone, apigenin and luteolin showed potent inhibitory effects on the proliferation of Hs578T, MDA-MB-231 and MCF-7 breast cancer cells in a concentration and time-dependent manner. The ability of flavone, apigenin and luteolin to inhibit the growth of breast cancer cells through apoptosis was confirmed by Hoechst33342 staining and the induction of sub-G1 phase of the cell cycle. Flavone, apigenin and luteolin induced forkhead box O3 (FOXO3a) expression by inhibiting Phosphoinositide 3-kinase (PI3K) and protein kinase B (PKB)/Akt. This subsequently elevated the expression of FOXO3a target genes, including the Cyclin-dependent kinase inhibitors p21Cip1 (p21) and p27kip1 (p27), which increased the levels of activated poly(ADP) polymerase (PARP) and cytochrome c.ConclusionTaken together, these data demonstrated that flavone, apigenin and luteolin induced cell cycle arrest and apoptosis in breast cancer cells through inhibiting PI3K/Akt activation and increasing FOXO3a activation, which suggest that flavone, apigenin and luteolin will be the potential leads for the preventing and treating of breast cancer.

Tumor metastasis is an important biological characteristic, which involves multiple genetic changes and cumulation. This genome-wide information contributes to an improved understanding of molecular alterations during lymph node metastasis in HCC. It may help clinicians to predict metastasis of lymph nodes and assist researchers in identifying novel therapeutic targets for metastatic HCC patients.

A series of lanostane-type triterpenes isolated from Ganoderma lucidum were identified as pairs of positional or stereo-isomers. Comparison of the 13C chemical shifts among these structurally related compounds allowed several empirical rules to be formulated. The correlation between 13C chemical shifts and stereochemical features was evident based on this empirical analysis.The fungus Ganoderma lucidum (Fr.) Karst (Polyporaceae), used in traditional Chinese medicine, has attracted great attention recently because of production of many highly oxygenated triterpenes and sterols with various biological activities (1-5). Biogenetically, the majority of the approximately 100 oxygenated triterpenes are derived from the lanostanoid skeleton with oxygenated functionalities mainly at the C-3, C-7, C-15, C-22, C-23, and C-26 carbons. Most interestingly from the structural and biosynthetic point of view, many triterpenes have been identified as pairs of stereoor positional isomers, particularly at C-3 (Figure 1). Accumulating 13C-and 'H-nmr spectroscopic information about these structurally related compounds allowed us to formulate several empirical rules for 13C-nmr signal assignments. Both for the characterization of new, related compounds and future biosynthetic studies, we report here the empirical rules which correlate stereochemical features and 13C chemical shifts.

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