title: Proximal promoter of the cytochrome P450 oxidoreductase gene: identification of microdeletions involving the untranslated exon 1 and critical function of the SP1 binding sites.
abstract: BACKGROUND
  POR (cytochrome P450 oxidoreductase) is a ubiquitously expressed gene encoding an electron donor to all microsomal P450 enzymes and several non-P450 enzymes. POR mutations cause an autosomal recessive disorder characterized by skeletal dysplasia, adrenal dysfunction, and disorders of sex development. Although recent studies have indicated the presence of a CpG-rich region characteristic of housekeeping genes around the untranslated exon 1 (exon 1U) and a tropic effect of thyroid hormone on POR expression via thyroid hormone receptor-β, detailed regulatory mechanisms for the POR expression remain to be clarified.
  
  
  OBJECTIVE
  Our objective was to report a pivotal element of the proximal promoter of POR.
  
  
  RESULTS
  We first studied three patients (cases 1-3) with POR deficiency due to compound heterozygosity with an p.R457H mutation and transcription failure of an apparently normal allele, by oligoarray comparative genomic hybridization and serial direct sequencing of the deletion fusion points. Consequently, a 2,487-bp microdeletion involving exon 1U was identified in case 1 and an identical 49,604-bp deletion involving exon 1U and exon 1 was found in cases 2 and 3. We next analyzed the 2,487-bp region commonly deleted in cases 1-3 by in silico analysis, DNA binding analysis, luciferase assays, and methylation analysis. The results showed a critical function of the evolutionally conserved SP1 binding sites just upstream of exon 1U, especially the binding site at the position -26/-17, in the transcription of POR.
  
  
  CONCLUSIONS
  The results suggest that the SP1 binding sites constitute an essential element of the POR proximal promoter.
authors: National Research Institute for Child Health and Development, Department of Molecular Endocrinology, Tokyo 157-8535, Japan.
authors: Shun
authors: S
authors: Soneda
authors: Takashi
authors: T
authors: Yazawa
authors: Maki
authors: M
authors: Fukami
authors: Masanori
authors: M
authors: Adachi
authors: Michiyo
authors: M
authors: Mizota
authors: Kenji
authors: K
authors: Fujieda
authors: Kaoru
authors: K
authors: Miyamoto
authors: Tsutomu
authors: T
authors: Ogata
mesh_terms: D054882:Antley-Bixler Syndrome Phenotype / Q000235:genetics*; D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics; D005091:Exons; D006801:Humans; D009251:NADPH-Ferrihemoprotein Reductase / Q000235:genetics*; D011401:Promoter Regions, Genetic; D017384:Sequence Deletion; D016329:Sp1 Transcription Factor / Q000235:genetics*
chemical_list: D016329:Sp1 Transcription Factor; D009251:NADPH-Ferrihemoprotein Reductase