Visualization of the dynamic interaction between nucleosomal histone H3K9 tri-methylation and HP1α chromodomain in living cells.

Histone lysine methylation is an epigenetic mark that can control gene expression. In particular, H3K9me3 contributes to transcriptional repression by regulating chromatin structure. Successful mitotic progression requires correct timing of chromatin structure changes, including epigenetic marks. However, spatiotemporal information on histone modifications in living cells remains limited. In this study, we created an FRET-based probe for live-cell imaging based on the HP1α chromodomain (HP1αCD), which binds to H3K9me3. The probe was incorporated into chromatin and the emission ratio decreased after treatment with histone methyltransferase inhibitors, indicating that it successfully traced dynamic changes in H3K9me3. Upon entry into mitosis, the probe's emission ratio transiently increased with a concomitant increase in H3K9me3, then exhibited a stepwise decrease, probably due to loss of HP1αCD binding caused by phosphorylation of H3S10 and demethylation of H3K9me3. This probe will be a useful tool for detecting dynamic changes in chromatin structure associated with HP1α.

Unveiling epidithiodiketopiperazine as a non-histone arginine methyltransferase inhibitor by chemical protein methylome analyses.

We present a chemical methylome analysis platform to evaluate the inhibitory activity of small molecules towards poorly characterized protein methyltransferases (PMTs), facsilitating to identify syn-HyPA-ETP-2 as a non-histone arginine methyltransferase inhibitor.

Epidithiodiketopiperazine as a pharmacophore for protein lysine methyltransferase G9a inhibitors: reducing cytotoxicity by structural simplification.

Chaetocin (1), a structurally complex epidithiodiketopiperazine (ETP) alkaloid produced by Chaetomium minutum, is a potent inhibitor of protein lysine methyltransferase G9a, which plays important roles in many biological processes. Here we present our synthetic investigations to identify a simple prototype G9a inhibitor structure based on structure-activity relationship (SAR) studies on chaetocin derivatives. The simple derivative PS-ETP-1 (14) was found to be a potent G9a inhibitor with greatly reduced cytotoxicity.

Unnatural enantiomer of chaetocin shows strong apoptosis-inducing activity through caspase-8/caspase-3 activation.

Chaetocin, a natural product isolated from Chaetomium species fungi, was reported to have various biological activities, including antitumor and antifungal activities. Recently, we reported the first total synthesis of chaetocin and its derivatives. Here, we examined the cell-death-inducing activity of these compounds in human leukemia HL-60 cells. The unnatural enantiomer of chaetocin (ent-chaetocin) was more potent than chaetocin, and was found to induce apoptosis through the caspase-8/caspase-3 activation pathway.

Total synthesis of (+)-chaetocin and its analogues: their histone methyltransferase G9a inhibitory activity.

The first total synthesis of (+)-chaetocin has been accomplished in nine steps starting from known N-Cbz-N-Me-serine using radical alpha-bromination reaction of diketopiperazine 10 and Co(I)-mediated reductive dimerization reaction of 12 as key reactions. The enantiomers show comparable inhibitory activity toward histone methyltransferase (HMT) G9a, but analogues without the sulfur functionality are inactive.