title: Allyl mercaptan, a garlic-derived organosulfur compound, inhibits histone deacetylase and enhances Sp3 binding on the P21WAF1 promoter.
abstract: Histone deacetylase (HDAC) inhibitors have the potential to derepress epigenetically silenced genes in cancer cells, leading to cell cycle arrest and apoptosis. In the present study, we screened several garlic-derived small organosulfur compounds for their ability to inhibit HDAC activity in vitro. Among the organosulfur compounds examined, allyl mercaptan (AM) was the most potent HDAC inhibitor. Molecular modeling, structure activity and enzyme kinetics studies with purified human HDAC8 provided evidence for a competitive mechanism (K(i) = 24 microM AM). In AM-treated human colon cancer cells, HDAC inhibition was accompanied by a rapid and sustained accumulation of acetylated histones in total cellular chromatin. Chromatin immunoprecipitation assays confirmed the presence of hyperacetylated histone H3 on the P21WAF1 gene promoter within 4 h of AM exposure, and there was increased binding of the transcription factor Sp3. At a later time, 24 h after AM treatment, there was enhanced binding of p53 in the distal enhancer region of the P21WAF1 gene promoter. These findings suggest a primary role for Sp3 in driving P21 gene expression after HDAC inhibition by AM, followed by the subsequent recruitment of p53. Induction of p21Waf1 protein expression was detected at time points between 3 and 72 h after AM treatment and coincided with growth arrest in G(1) of the cell cycle. The results are discussed in the context of other anticarcinogenic mechanisms ascribed to garlic organosulfur compounds and the metabolic conversion of such compounds to potential HDAC inhibitors in situ.
authors.affiliation: Linus Pauling Institute, Oregon State University, 571 Weniger Hall, Corvallis, OR 97331-6512, USA.
authors.forename: Hui
authors.initials: H
authors.lastname: Nian
authors.forename: Barbara
authors.initials: B
authors.lastname: Delage
authors.forename: John T
authors.initials: JT
authors.lastname: Pinto
authors.forename: Roderick H
authors.initials: RH
authors.lastname: Dashwood
mesh_terms: D000107:Acetylation; D000498:Allyl Compounds / Q000494:pharmacology*; D001667:Binding, Competitive; D002453:Cell Cycle / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D047369:Chromatin Immunoprecipitation; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000235:genetics* / Q000378:metabolism; D005434:Flow Cytometry; D005737:Garlic; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects*; D019073:HT29 Cells; D056284:Histone Deacetylase 1; D056572:Histone Deacetylase Inhibitors; D006655:Histone Deacetylases / Q000378:metabolism; D006657:Histones / Q000378:metabolism; D006801:Humans; D015151:Immunoblotting; D008958:Models, Molecular; D011401:Promoter Regions, Genetic / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016329:Sp1 Transcription Factor / Q000378:metabolism; D051705:Sp3 Transcription Factor / Q000378:metabolism*; D014158:Transcription, Genetic / Q000187:drug effects; D015533:Transcriptional Activation; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism
chemical_list: D000498:Allyl Compounds; C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; D056572:Histone Deacetylase Inhibitors; D006657:Histones; D012333:RNA, Messenger; D016329:Sp1 Transcription Factor; D016159:Tumor Suppressor Protein p53; D051705:Sp3 Transcription Factor; C110550:HDAC1 protein, human; D056284:Histone Deacetylase 1; D006655:Histone Deacetylases