Sp1 acetylation is associated with loss of DNA binding at promoters associated with cell cycle arrest and cell death in a colon cell line.
Butyrate, a known histone deacetylase inhibitor (HDACi) and product of fibre fermentation, is postulated to mediate the protective effect of dietary fibre against colon cancer. The transcription factor Sp1 is a target of acetylation and is known to be associated with class I HDACs, including HDAC1. Sp1 is a ubiquitous transcription factor and Sp1-regulated genes include those involved in cell cycle regulation, apoptosis and lipogenesis: all major pathways in cancer development. The only known acetylated residue of Sp1 is lysine703 which resides in the DNA binding domain. Here we show that acetylated Sp1 loses p21- and bak-promoter -binding function in vitro. Furthermore treatment with a panel of HDAC inhibitors showed clustering of activities for a subset of inhibitors, causing G2 cell cycle arrest, Sp1 acetylation, p21 and Bak over-expression, all with very similar EC50 concentrations. These HDACi activities were not distributed according to the molecular class of compound. In order to mimic loss of binding, an siRNA strategy was used to reduce Sp1 expression. This resulted in altered expression of multiple elements of the p53/p21 pathway. Taken together our data suggest a mechanistic model for the chemopreventive actions of butyrate in colon epithelial cells, and provide new insight into the differential activities some classes of HDAC inhibitors.
Department of Oncology, University of Sheffield, Medical School, Beech Hill Road, Sheffield, UK.
Jennifer S
JS
Waby
Haridasan
H
Chirakkal
ChenWei
C
Yu
Gareth J
GJ
Griffiths
Roderick S P
RS
Benson
Colin D
CD
Bingle
Bernard M
BM
Corfe
D000107:Acetylation / Q000187:drug effects*; D015153:Blotting, Western; D002087:Butyrates / Q000494:pharmacology; D002453:Cell Cycle / Q000187:drug effects*; D016923:Cell Death / Q000187:drug effects; D003106:Colon / Q000166:cytology*; D019295:Computational Biology; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000235:genetics / Q000378:metabolism; D004247:DNA / Q000378:metabolism*; D045325:HCT116 Cells; D056572:Histone Deacetylase Inhibitors / Q000494:pharmacology; D006801:Humans; D020411:Oligonucleotide Array Sequence Analysis; D016133:Polymerase Chain Reaction; D011485:Protein Binding / Q000187:drug effects; D034741:RNA, Small Interfering; D016329:Sp1 Transcription Factor / Q000235:genetics / Q000378:metabolism*; D050998:bcl-2 Homologous Antagonist-Killer Protein / Q000235:genetics / Q000378:metabolism
D002087:Butyrates; D050759:Cyclin-Dependent Kinase Inhibitor p21; D056572:Histone Deacetylase Inhibitors; D034741:RNA, Small Interfering; D016329:Sp1 Transcription Factor; D050998:bcl-2 Homologous Antagonist-Killer Protein; D004247:DNA