title: Promoter methylation inhibits BRD7 expression in human nasopharyngeal carcinoma cells.
abstract: BACKGROUND
  Nasopharyngeal carcinoma (NPC) is a head and neck malignancy with high occurrence in South-East Asia and Southern China. Recent findings suggest that epigenetic inactivation of multiple tumor suppressor genes plays an important role in the tumourigenesis of NPC. BRD7 is a NPC-associated bromodomain gene that exhibits a much higher-level of mRNA expression in normal than in NPC biopsies and cell lines. In this study, we explored the role of DNA methylation in regulation of BRD7 transcription.
  
  
  METHODS
  The presence of CpG islands within BRD7 promoter was predicted by EMBOSS CpGplot and Softberry CpGFinder, respectively. Nested methylation-specific PCR and RT-PCR were employed to detect the methylation status of BRD7 promoter and the mRNA expression of BRD7 gene in tumor cell lines as well as clinical samples. Electrophoretic mobility shift assays (EMSA) and luciferase assay were used to detect the effects of cytosine methylation on the nuclear protein binding to BRD7 promoter.
  
  
  RESULTS
  We found that DNA methylation suppresses BRD7 expression in NPC cells. In vitro DNA methylation in NPC cells silenced BRD7 promoter activity and inhibited the binding of the nuclear protein (possibly Sp1) to Sp1 binding sites in the BRD7 promoter. In contrast, inhibition of DNA methylation augments induction of endogenous BRD7 mRNA in NPC cells. We also found that methylation frequency of BRD7 promoter is much higher in the tumor and matched blood samples from NPC patients than in the blood samples from normal individuals.
  
  
  CONCLUSIONS
  BRD7 promoter demethylation is a prerequisite for high level induction of BRD7 gene expression. DNA methylation of BRD7 promoter might serve as a diagnostic marker in NPC.
authors.affiliation: Cancer Research Institute, Xiang-Ya School of Medicine, Central South University, Changsha, Hunan, PR China. huayingcsu@yahoo.com.cn
authors.forename: Huaying
authors.initials: H
authors.lastname: Liu
authors.forename: Liming
authors.initials: L
authors.lastname: Zhang
authors.forename: Zhaoxia
authors.initials: Z
authors.lastname: Niu
authors.forename: Ming
authors.initials: M
authors.lastname: Zhou
authors.forename: Cong
authors.initials: C
authors.lastname: Peng
authors.forename: Xiayu
authors.initials: X
authors.lastname: Li
authors.forename: Tan
authors.initials: T
authors.lastname: Deng
authors.forename: Lei
authors.initials: L
authors.lastname: Shi
authors.forename: Yixin
authors.initials: Y
authors.lastname: Tan
authors.forename: Guiyuan
authors.initials: G
authors.lastname: Li
mesh_terms: D001483:Base Sequence; D001665:Binding Sites; D002277:Carcinoma / Q000235:genetics* / Q000378:metabolism*; D045744:Cell Line, Tumor; D002868:Chromosomal Proteins, Non-Histone / Q000235:genetics* / Q000378:metabolism*; D018899:CpG Islands; D003596:Cytosine / Q000737:chemistry; D019175:DNA Methylation; D044127:Epigenesis, Genetic; D006367:HeLa Cells; D006801:Humans; D008969:Molecular Sequence Data; D009303:Nasopharyngeal Neoplasms / Q000235:genetics* / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D017434:Protein Structure, Tertiary; D000092468:Bromodomain Containing Proteins
chemical_list: D002868:Chromosomal Proteins, Non-Histone; D003596:Cytosine; C485694:BRD7 protein, human; D000092468:Bromodomain Containing Proteins
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