title: SP1 regulates the transcription of BMPR1A.
abstract: BACKGROUND
  BMPR1A is a cell surface receptor in the bone morphogenetic protein (BMP) pathway. Mutations in BMPR1A predispose to juvenile polyposis (JP). Sp1 and related proteins are widely expressed regulators of gene transcription, including members of the BMP pathway. We set out to identify important transcription factor binding sites (TFBS) in the recently identified BMPR1A promoter and to assess for the role of Sp1 and associated proteins in its regulation.
  
  
  METHODS
  The BMPR1A promoter was cloned into a luciferase reporter vector. Deletion fragments of this promoter insert were then constructed, of varying lengths and opposing directions, and were used to transfect HEK-293 and CRL-1459 cells. In silico analysis was performed to screen for relevant TFBS. Site-directed mutagenesis (SDM) was then employed to individually disrupt these TFBS in the wild-type (WT) vector. SDM constructs were then assessed for activity.
  
  
  RESULTS
  Light activity from the deletion constructs ranged between 3% and 129% of the WT promoter. ModelInspector identified eight potential binding sites for Sp1- and Sp1-associated proteins that mapped to areas of marked loss or gain of activity from the deletion constructs. SDM of these TFBS led to a drop in activity in five mutants, which included 3 Sp1 sites, an ETSF site, and NFκB site.
  
  
  CONCLUSIONS
  By combining in silico analysis and experimental data, Sp1 was found to be a candidate factor that likely plays a role in the transcriptional regulation of BMPR1A. This study potentially provides further insight toward the molecular basis of JP, and suggests that Sp1 plays a role in BMP signaling.
authors.affiliation: Department of Surgery, University of Iowa Carver College of Medicine, Iowa City, Iowa, USA.
authors.forename: Fadi S
authors.initials: FS
authors.lastname: Dahdaleh
authors.forename: Jennifer C
authors.initials: JC
authors.lastname: Carr
authors.forename: Daniel
authors.initials: D
authors.lastname: Calva
authors.forename: James R
authors.initials: JR
authors.lastname: Howe
authors.forename: James R
authors.initials: JR
authors.lastname: Howe
mesh_terms: D001483:Base Sequence; D052005:Bone Morphogenetic Protein Receptors, Type I / Q000235:genetics*; D003106:Colon / Q000166:cytology; D005347:Fibroblasts / Q000166:cytology; D005786:Gene Expression Regulation / Q000502:physiology; D057809:HEK293 Cells; D006801:Humans; D008156:Luciferases / Q000235:genetics; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D011401:Promoter Regions, Genetic / Q000502:physiology; D016329:Sp1 Transcription Factor / Q000378:metabolism*; D014158:Transcription, Genetic / Q000502:physiology*
chemical_list: D016329:Sp1 Transcription Factor; D008156:Luciferases; C498211:BMPR1A protein, human; D052005:Bone Morphogenetic Protein Receptors, Type I