Genomic, transcriptomic, and metabolomic analysis of Oldenlandia corymbosa reveals the biosynthesis and mode of action of anti-cancer metabolites.

Plants accumulate a vast array of secondary metabolites, which constitute a natural resource for pharmaceuticals. Oldenlandia corymbosa belongs to the Rubiaceae family, and has been used in traditional medicine to treat different diseases, including cancer. However, the active metabolites of the plant, their biosynthetic pathway and mode of action in cancer are unknown. To fill these gaps, we exposed this plant to eight different stress conditions and combined different omics data capturing gene expression, metabolic profiles, and anti-cancer activity. Our results show that O. corymbosa extracts are active against breast cancer cell lines and that ursolic acid is responsible for this activity. Moreover, we assembled a high-quality genome and uncovered two genes involved in the biosynthesis of ursolic acid. Finally, we also revealed that ursolic acid causes mitotic catastrophe in cancer cells and identified three high-confidence protein binding targets by Cellular Thermal Shift Assay (CETSA) and reverse docking. Altogether, these results constitute a valuable resource to further characterize the biosynthesis of active metabolites in the Oldenlandia group, while the mode of action of ursolic acid will allow us to further develop this valuable compound.

Coordination of chromosome alignment and mitotic progression by the chromosome-based Ran signal.

Mitotic spindle assembly and chromosome segregation are controlled by the cell cycle machinery and by the guanosine triphosphatase Ran (RanGTPase). We developed a spatial model that allowed us to simulate RanGTP production with different degrees of chromosome alignment in mitosis. Aided by this model, we defined three factors that modulate mitotic RanGTP gradients and mitotic progression in somatic cells. First, the completion of chromosome alignment at the metaphase plate could generate highest local RanGTP concentrations on chromosomes that could lead to spindle checkpoint silencing and metaphase-anaphase transition. Second, the concentration of RanGTP-transport-receptor (represented by RanGTP-importin beta) and its spatial distribution are very sensitive to the level of RanBP1. Reduction of RanBP1 leads to an elevated RanGTP-transport-receptor concentration throughout the cell, which disrupts spindle assembly and weakens spindle checkpoint control. Finally, chromosomal RanGTP production could be dampened by a reduction of RCC1 phosphorylation by Cdc2 in mitosis. Our spatial simulation of RanGTP production using individual chromosomes should provide means to further understand how the Ran system and the cell cycle machinery coordinately regulate mitosis.

Chromosome alignment and segregation regulated by ubiquitination of survivin.

Proper chromosome segregation requires the attachment of sister kinetochores to microtubules from opposite spindle poles to form bi-oriented chromosomes on the metaphase spindle. The chromosome passenger complex containing Survivin and the kinase Aurora B regulates this process from the centromeres. We report that a de-ubiquitinating enzyme, hFAM, regulates chromosome alignment and segregation by controlling both the dynamic association of Survivin with centromeres and the proper targeting of Survivin and Aurora B to centromeres. Survivin is ubiquitinated in mitosis through both Lys(48) and Lys(63) ubiquitin linkages. Lys(63) de-ubiquitination mediated by hFAM is required for the dissociation of Survivin from centromeres, whereas Lys(63) ubiquitination mediated by the ubiquitin binding protein Ufd1 is required for the association of Survivin with centromeres. Thus, ubiquitinaton regulates dynamic protein-protein interactions and chromosome segregation independently of protein degradation.