Magic™ Anti-CDC25A (Phospho S124) polyclonal antibody

Bioassay-guided fractionation led to the discovery of a novel rieo-clerodane diterpenoid, scutebarbalactone VN (Ba1A: 8,13-epoxy-3-en-7-hydroxy-6,11-O-dibenzoyl-15,16-clerodanolide), from the methanol extract of the whole-plant of Vietnamese Scutellaria barbata D. Don. A microarray technique combined with bioinformatic analyses showed that Ba1A could inhibit cell cycle pathways by downregulating genes such as CDC25A and AURKA. Ba1A also showed the potential to reactivate downregulated genes in hepatocellular carcinoma cells and genes in antioxidant pathways such as HMOX1 and HSPA1A. Querying Connectivity map 2.0 resulted in a match of the Ba1A-modulated gene signature with that of 10 known compounds, most of which are currently marketed chemotherapy drugs. The highest matching scores belonged to lomustine, semustine, and withaferin A. Lomustine and semustine were found to alkylate DNA and RNA, while withaferin A inhibits nuclear factor kappa B (NF-kappa B) activity. A luciferase reporter assay was also conducted on 293/NF-kappa B human embryonic kidney cells that had been transfected with the NF-kappa B-luciferase plasmid to verify the anticancer activity of Ba1A. The assay showed that Ba1A effectively blocked NF-kappa B with an IC50 of 38.6 +/- 0.05 mu M.

Shelterin component TRF2 prevents ATM activation, while POT1 represses ATR signalling at telomeres. Here, we investigate the mechanism of G2/M arrest triggered by telomeres uncapped through TRF2 or POT1 inhibition in human cells. We find that telomere damage-activated ATR and ATM phosphorylate p53, as well as CHK1 and CHK2, thus activating two independent pathways to prevent progression into mitosis with uncapped telomeres. Surprisingly, telomere damage targets the CDC25C phosphatase for proteasome degradation in G2/M. CHK1/CHK2-dependent phosphorylation of CDC25C at Ser 216 is required for CDC25C nuclear export and destruction, which in turn acts to sustain the G2/M arrest elicited by TRF2- or POT1-depleted telomeres. In addition, CDC25C is transcriptionally downregulated by p53 in response to telomere damage. These mechanisms are distinct from the canonical DNA damage response to ionizing radiation, which triggers cell-cycle arrest through CDC25A destruction. Thus, dysfunctional telomeres promote ATM/ATR-dependent degradation of CDC25C phosphatase to block mitotic entry, thereby preventing telomere dysfunction-driven genomic instability. The EMBO Journal (2012) 31, 3398-3410. doi:10.1038/emboj.2012.191; Published online 27 July 2012