title: Nuclear respiratory factor 1 mediates the transcription initiation of insulin-degrading enzyme in a TATA box-binding protein-independent manner.
abstract: CpG island promoters often lack canonical core promoter elements such as the TATA box, and have dispersed transcription initiation sites. Despite the prevalence of CpG islands associated with mammalian genes, the mechanism of transcription initiation from CpG island promoters remains to be clarified. Here we investigate the mechanism of transcription initiation of the CpG island-associated gene, insulin-degrading enzyme (IDE). IDE is ubiquitously expressed, and has dispersed transcription initiation sites. The IDE core promoter locates within a 32-bp region, which contains three CGGCG repeats and a nuclear respiratory factor 1 (NRF-1) binding motif. Sequential mutation analysis indicates that the NRF-1 binding motif is critical for IDE transcription initiation. The NRF-1 binding motif is functional, because NRF-1 binds to this motif in vivo and this motif is required for the regulation of IDE promoter activity by NRF-1. Furthermore, the NRF-1 binding site in the IDE promoter is conserved among different species, and dominant negative NRF-1 represses endogenous IDE expression. Finally, TATA-box binding protein (TBP) is not associated with the IDE promoter, and inactivation of TBP does not abolish IDE transcription, suggesting that TBP is not essential for IDE transcription initiation. Our studies indicate that NRF-1 mediates IDE transcription initiation in a TBP-independent manner, and provide insights into the potential mechanism of transcription initiation for other CpG island-associated genes.
authors.affiliation: Protein Science Key Laboratory of the Ministry of Education, Department of Biological Sciences and Biotechnology, School of Medicine, Tsinghua University, Beijing, China.
authors.forename: Lang
authors.initials: L
authors.lastname: Zhang
authors.forename: Qingyang
authors.initials: Q
authors.lastname: Ding
authors.forename: Zhao
authors.initials: Z
authors.lastname: Wang
mesh_terms: D000818:Animals; D018899:CpG Islands / Q000502:physiology; D015971:Gene Expression Regulation, Enzymologic / Q000502:physiology*; D006367:HeLa Cells; D006801:Humans; D007339:Insulysin / Q000096:biosynthesis* / Q000235:genetics; D051379:Mice; D041681:NIH 3T3 Cells; D051266:Nuclear Respiratory Factor 1 / Q000235:genetics / Q000378:metabolism*; D020218:Response Elements / Q000502:physiology; D016385:TATA Box / Q000502:physiology*; D061785:Transcription Initiation, Genetic / Q000502:physiology*
chemical_list: C495633:NRF1 protein, human; C495634:Nrf1 protein, mouse; D051266:Nuclear Respiratory Factor 1; D007339:Insulysin