title: The promoter activity of human Mfn2 depends on Sp1 in vascular smooth muscle cells.
abstract: OBJECTIVE
  Mitofusin-2 (Mfn2) expression is dysregulated in vascular proliferative disorders and its overexpression attenuates the proliferation of vascular smooth muscle cells (VSMCs) and neointimal lesion development after balloon angioplasty. We sought to gain insight into the mechanisms that control Mfn2 expression in VSMCs.
  
  
  RESULTS
  We cloned and characterized 2 kb of the 5'-flanking region of the human Mfn2 gene. Its TATA-less promoter contains a CpG island. In keeping with this, 5'-rapid amplification of cDNA ends revealed six transcriptional start sites (TSSs), of which TSS2 and TSS5 were the most frequently used. The strong CpG island was found to be non-methylated under conditions characterized by large differences in Mfn2 gene expression. The proximal Mfn2 promoter contains six putative Sp1 motifs. Sp1 binds to the Mfn2 promoter and its overexpression activates the Mfn2 promoter in VSMCs. Chemical inhibition of Sp1 reduced Mfn2 expression, and Sp1 silencing reduced transcriptional activity of the Mfn2 promoter. In keeping with this view, Sp1 and Mfn2 mRNA levels were down-regulated in the aorta early after an atherogenic diet in apolipoprotein E-knockout mice or in VSMCs cultured in the presence of low serum.
  
  
  CONCLUSIONS
  Sp1 is a key factor in maintaining basal Mfn2 transcription in VSMCs. Given the anti-proliferative actions of Mfn2, Sp1-induced Mfn2 transcription may represent a mechanism for prevention of VSMC proliferation and neointimal lesion and development.
authors.affiliation: Institute of Research in Biomedicine, Parc Científic de Barcelona, Barcelona, Spain.
authors.forename: Eleonora
authors.initials: E
authors.lastname: Sorianello
authors.forename: Francesc X
authors.initials: FX
authors.lastname: Soriano
authors.forename: Sergio
authors.initials: S
authors.lastname: Fernández-Pascual
authors.forename: Ana
authors.initials: A
authors.lastname: Sancho
authors.forename: Deborah
authors.initials: D
authors.lastname: Naon
authors.forename: Marian
authors.initials: M
authors.lastname: Vila-Caballer
authors.forename: Herminia
authors.initials: H
authors.lastname: González-Navarro
authors.forename: José
authors.initials: J
authors.lastname: Portugal
authors.forename: Vicente
authors.initials: V
authors.lastname: Andrés
authors.forename: Manuel
authors.initials: M
authors.lastname: Palacín
authors.forename: Antonio
authors.initials: A
authors.lastname: Zorzano
mesh_terms: D000818:Animals; D001057:Apolipoproteins E / Q000172:deficiency / Q000235:genetics; D050197:Atherosclerosis / Q000378:metabolism / Q000473:pathology / Q000517:prevention & control; D001483:Base Sequence; D001665:Binding Sites; D002460:Cell Line; D018899:CpG Islands; D019175:DNA Methylation; D004195:Disease Models, Animal; D020558:GTP Phosphohydrolases / Q000235:genetics* / Q000378:metabolism; D005786:Gene Expression Regulation; D006801:Humans; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D024101:Mitochondrial Proteins / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D032389:Myocytes, Smooth Muscle / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D058426:Neointima / Q000378:metabolism / Q000473:pathology / Q000517:prevention & control; D011401:Promoter Regions, Genetic; D034622:RNA Interference; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D016329:Sp1 Transcription Factor / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D024363:Transcription Initiation Site; D015533:Transcriptional Activation / Q000187:drug effects; D014162:Transfection
chemical_list: D001057:Apolipoproteins E; D024101:Mitochondrial Proteins; D012333:RNA, Messenger; D016329:Sp1 Transcription Factor; D020558:GTP Phosphohydrolases; C470018:MFN2 protein, human