Description

• A naturally occurring cell-permeable Chaetomium fungal epi-dithio-diketopiperazine that potently inhibits the H3K9 histone methyltransferase activity of Drosophila melanogaster SU(VAR)3-9 and its human homologue SUV39H1 (IC 50 = 600 and 800 nM, respectively) in a SAM-competitive manner, while exhibiting much reduced potency against murine G9a or Neurospora crassa DIM5 H3K9 HMT (IC 50 = 2.5 and 3μM, respectively) and no activity against the H3K27 HMTase activity of Drosophila E(z), the H3K4 activity of bacterial SET7/9, or the H4K20 activity of bacterial PRSET7
• Although the reduction of intramolecular disulfide bonds of Chaetocin does not affect its HMTase inhibitory activity in cell-free enzymatic assays, the integrity of the disulfide bonds is shown to be essential for its cellular uptake
• Myeloma cell lines as well as myeloma cells isolated from patients are shown to be especially susceptible to death upon H 2 O 2 or Chaetocin treatment due to their heightened sensitivity to cellular oxidative stress induced by these agents.