Helenalin Acetate, a Natural Sesquiterpene Lactone with Anti-inflammatory and Anti-cancer Activity, Disrupts the Cooperation of CCAAT Box/Enhancer-binding Protein β (C/EBPβ) and Co-activator p300.
Recent work has demonstrated pro-oncogenic functions of the transcription factor CCAAT box/enhancer-binding protein β (C/EBPβ) in various tumors, implicating C/EBPβ as an interesting target for the development of small-molecule inhibitors. We have previously discovered that the sesquiterpene lactone helenalin acetate, a natural compound known to inhibit NF-κB, is a potent C/EBPβ inhibitor. We have now examined the inhibitory mechanism of helenalin acetate in more detail. We demonstrate that helenalin acetate is a significantly more potent inhibitor of C/EBPβ than of NF-κB. Our work shows that helenalin acetate inhibits C/EBPβ by binding to the N-terminal part of C/EBPβ, thereby disrupting the cooperation of C/EBPβ with the co-activator p300. C/EBPβ is expressed in several isoforms from alternative translational start codons. We have previously demonstrated that helenalin acetate selectively inhibits only the full-length (liver-enriched activating protein* (LAP*)) isoform but not the slightly shorter (LAP) isoform. Consistent with this, helenalin acetate binds to the LAP* but not to the LAP isoform, explaining why its inhibitory activity is selective for LAP*. Although helenalin acetate contains reactive groups that are able to interact covalently with cysteine residues, as exemplified by its effect on NF-κB, the inhibition of C/EBPβ by helenalin acetate is not due to irreversible reaction with cysteine residues of C/EBPβ. In summary, helenalin acetate is the first highly active small-molecule C/EBPβ inhibitor that inhibits C/EBPβ by a direct binding mechanism. Its selectivity for the LAP* isoform also makes helenalin acetate an interesting tool to dissect the functions of the LAP* and LAP isoforms.
From the Institute for Biochemistry and.
Anke
A
Jakobs
From the Institute for Biochemistry and.
Simone
S
Steinmann
From the Institute for Biochemistry and.
Sarah Marie
SM
Henrich
the Institute for Pharmaceutical Biology and Phytochemistry, Westfälische Wilhelms-Universität, D-48149 Münster, Germany.
Thomas J
TJ
Schmidt
From the Institute for Biochemistry and klempna@uni-muenster.de.
Karl-Heinz
KH
Klempnauer
D041721:3T3-L1 Cells; D000818:Animals; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000493:pharmacokinetics / Q000494:pharmacology*; D000972:Antineoplastic Agents, Phytogenic / Q000493:pharmacokinetics / Q000494:pharmacology*; D022782:CCAAT-Enhancer-Binding Protein-beta / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D051379:Mice; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism; D020033:Protein Isoforms / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D012717:Sesquiterpenes / Q000493:pharmacokinetics / Q000494:pharmacology*; D045789:Sesquiterpenes, Guaiane; D050880:p300-CBP Transcription Factors / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism
D000894:Anti-Inflammatory Agents, Non-Steroidal; D000972:Antineoplastic Agents, Phytogenic; D022782:CCAAT-Enhancer-Binding Protein-beta; C545013:Cebpb protein, mouse; D016328:NF-kappa B; D020033:Protein Isoforms; D012717:Sesquiterpenes; D045789:Sesquiterpenes, Guaiane; C001329:helenalin; D050880:p300-CBP Transcription Factors
CCAAT-enhancer-binding protein (C/EBP); E1A-binding protein p300 (P300); NF-kappa B (NF-KB); adipocyte; helenalin acetate; inhibitor; small-molecule