On the Histone Lysine Methyltransferase Activity of Fungal Metabolite Chaetocin

Abstract

Histone lysine methyltransferases (HKMTs) are an important class of targets for epigenetic therapy. 1 (chaetocin), an epidithiodiketopiperazine (ETP) natural product, has been reported to be a specific inhibitor of the SU(VAR)3-9 class of HKMTs. We have studied the inhibition of the HKMT G9a by 1 and functionally related analogues. Our results reveal that only the structurally unique ETP core is required for inhibition, and such inhibition is time-dependent and irreversible (in the absence of DTT), ultimately resulting in protein denaturation. Mass spectrometric data provide a molecular basis for this effect, demonstrating covalent adduct formation between 1 and the protein. This provides a potential rationale for the selectivity observed in the inhibition of a variety of HKMTs by 1 in vitro and has implications for the activity of ETPs against these important epigenetic targets.

Inhibition of Histone Methyltransferases SUV39H1 and G9a Leads to Neuroprotection in an in vitro Model of Cerebral Ischemia

“…33 The exclusive inhibitory specificity toward SUV39 family members as well as the exact mechanism of action of chaetocin are a matter of debate; its inhibitory potency against SUV39H1 and G9a, however, has been confirmed by several research groups. 22,23,34,35 In the present study, chaetocin was for the first time employed in neurons. We could hence identify it as a novel neuroprotective agent, which might promote survival not only in models of cerebral ischemia but also in other models of neurodegeneration.…”

Adolescent THC exposure in female rats leads to cognitive deficits through a mechanism involving chromatin modifications in the prefrontal cortex

“…It is therefore possible that the increase of Suv39H1 we observed in our study could be a potential mechanism through which THC acts on chromatin to induce longlasting effects. Indeed, daily coadministration of THC and chaetocin, an inhibitor of the HMTs acting on H3K9, 34,35 prevented the increase in H3K9me3 as well as the large gene downregulation induced by THC in the PFC. Specifically, chaetocin prevented the re pression of 19 of 29 genes, suggesting that their expression could be mediated by H3K9me3 levels.…”

“…To investigate the possible role of H3K9me3 increase induced by adolescent THC exposure, [8][9][10][11][12][13] we administered chaetocin, an inhibitor of the HMTs SUV39H1 and G9a, 34,35 simultane ously with THC treatment. To establish the active dose of chaetocin in vivo, we first tested 2 different intraperitoneal doses (0.05 mg/kg and 0.1 mg/kg), and 24 hours after the in jection, we investigated H3K9me3 levels.…”

Resistance is not futile: gliotoxin biosynthesis, functionality and utility

“…23,No. 7 Histone H3 lysine 9 (H3K9) methyltransferase inhibition Gliotoxin, and indeed other ETPs (e.g., chetomin and chaetocin), are inhibitors of H3K9 methyltransferases, which has been demonstrated using recombinant enzymes [45,46]. The disulfide bond of ETP molecules is crucial for this inhibition because ETPs in which the thiols are rendered unreactive (e.g., bis-dethiobisacetylgliotoxin and chaetocin with methylated sulfur groups) do not display inhibitory abilities [45,46].…”

“…7 Histone H3 lysine 9 (H3K9) methyltransferase inhibition Gliotoxin, and indeed other ETPs (e.g., chetomin and chaetocin), are inhibitors of H3K9 methyltransferases, which has been demonstrated using recombinant enzymes [45,46]. The disulfide bond of ETP molecules is crucial for this inhibition because ETPs in which the thiols are rendered unreactive (e.g., bis-dethiobisacetylgliotoxin and chaetocin with methylated sulfur groups) do not display inhibitory abilities [45,46]. While direct investigations of the effects of gliotoxin on histone H3K9 methyltransferases in A. fumigatus or other filamentous fungi have not been performed to the best of our knowledge, functional studies of histone-modifying enzymes have been carried out (reviewed in [47]).…”