PMID- 23047008
OWN - NLM
STAT- MEDLINE
DCOM- 20130326
LR  - 20161125
IS  - 1090-2104 (Electronic)
IS  - 0006-291X (Linking)
VI  - 428
IP  - 1
DP  - 2012 Nov 9
TI  - A possible gene silencing mechanism: hypermethylation of the Keap1 promoter 
      abrogates binding of the transcription factor Sp1 in lung cancer cells.
PG  - 80-5
LID - S0006-291X(12)01934-1 [pii]
LID - 10.1016/j.bbrc.2012.10.010 [doi]
AB  - Hypermethylation often leads to gene silencing; however, the mechanism 
      responsible for the low expression resulting from hypermethylation of the tumor 
      suppressor gene Kelch-like ECH-associating protein 1 (Keap1) in human lung cancer 
      cell lines remains unclear. In this study, using promoter deletion and site 
      mutagenesis assays, we determined that one transcription factor stimulating 
      protein-1 (Sp1) regulatory element in the Keap1 promoter region was important for 
      the transcription of Keap1 in A549 cells. We demonstrated that the transcription 
      factor Sp1 can directly bind to this element in the normal bronchial epithelial 
      BEAS-2B cell line but not in A549 cells, as assessed with chromatin 
      immunoprecipitation (ChIP). EMSAs and supershift assays also showed that CpG 
      island methylation could abrogate Sp1 binding to the Keap1 promoter. Moreover, 
      Keap1 mRNA decreased by 50% after the knock-down of Sp1 with siRNA in BEAS-2B 
      cells, whereas the over-expression of Sp1 led to a dramatic increase in Keap1 
      promoter activity. The treatment of A549 cells with 5-aza-2'-deoxycytidine 
      restored the binding of Sp1 to the promoter and Keap1 expression. Our results 
      indicate that Sp1 is essential for Keap1 expression and that promoter methylation 
      blocks Sp1 binding in A549 cells. These results demonstrate that hypermethylation 
      may act as an epigenetic gene silencing mechanism, i.e., the inhibition of Sp1 
      binding to the hypermethylated Keap1 promoter in lung cancer cells, which 
      suggests new approaches to lung cancer treatment.
CI  - Copyright (c) 2012 Elsevier Inc. All rights reserved.
FAU - Guo, Duo
AU  - Guo D
AD  - Department of Histology and Embryology, School of Basic Medical Sciences, Capital 
      Medical University, Beijing 100069, China.
FAU - Wu, Bo
AU  - Wu B
FAU - Yan, Jihong
AU  - Yan J
FAU - Li, Xiaoshuang
AU  - Li X
FAU - Sun, Haimei
AU  - Sun H
FAU - Zhou, Deshan
AU  - Zhou D
LA  - eng
PT  - Journal Article
PT  - Research Support, Non-U.S. Gov't
DEP - 20121006
PL  - United States
TA  - Biochem Biophys Res Commun
JT  - Biochemical and biophysical research communications
JID - 0372516
RN  - 0 (Intracellular Signaling Peptides and Proteins)
RN  - 0 (KEAP1 protein, human)
RN  - 0 (Kelch-Like ECH-Associated Protein 1)
RN  - 0 (Sp1 Transcription Factor)
SB  - IM
MH  - Binding Sites
MH  - Cell Line, Tumor
MH  - *DNA Methylation
MH  - *Gene Expression Regulation, Neoplastic
MH  - Gene Knockdown Techniques
MH  - *Gene Silencing
MH  - Humans
MH  - Intracellular Signaling Peptides and Proteins/*genetics
MH  - Kelch-Like ECH-Associated Protein 1
MH  - Lung Neoplasms/*genetics
MH  - Promoter Regions, Genetic
MH  - Sp1 Transcription Factor/genetics/*metabolism
EDAT- 2012/10/11 06:00
MHDA- 2013/03/27 06:00
CRDT- 2012/10/11 06:00
PHST- 2012/09/21 00:00 [received]
PHST- 2012/10/02 00:00 [accepted]
PHST- 2012/10/11 06:00 [entrez]
PHST- 2012/10/11 06:00 [pubmed]
PHST- 2013/03/27 06:00 [medline]
AID - S0006-291X(12)01934-1 [pii]
AID - 10.1016/j.bbrc.2012.10.010 [doi]
PST - ppublish
SO  - Biochem Biophys Res Commun. 2012 Nov 9;428(1):80-5. doi: 
      10.1016/j.bbrc.2012.10.010. Epub 2012 Oct 6.