Molecular dissection of the Schwann cell specific promoter of the PMP22 gene

• Published in: Gene 2000-05, Vol.248 (1), p.223-231
• Main Authors: Sabéran-Djoneidi, Délara, Sanguedolce, Véronique, Assouline, Zahra, Lévy, Nicolas, Passage, Edith, Fontés, Michel
• Format: Article
• Language: English
• Subjects: 3T3 Cells; Animals; Base Sequence; beta-Galactosidase - genetics; Binding Sites - drug effects; Cell Line; Charcot-Marie-Tooth disease 1A; Charcot–Marie–Tooth disease; Cloning, Molecular; Dinucleotide Repeats; DNA - chemistry; DNA - genetics; DNA - metabolism; Humans; Mice; Molecular Sequence Data; Myelin; Myelin Proteins - genetics; Myelin Proteins - metabolism; Peripheral neuropathies; PMP22; PMP22 gene; Polymorphism, Genetic; Promoter; Promoter Regions, Genetic - genetics; Recombinant Fusion Proteins - genetics; Schwann cells; Schwann Cells - cytology; Schwann Cells - metabolism; Sequence Analysis, DNA; Transcription Factors - metabolism; Transfection
• ISSN: 0378-1119; 1879-0038
• DOI: 10.1016/S0378-1119(00)00116-5

PMP22, one of the major components of myelin, is overexpressed in Charcot–Marie–Tooth type 1A (CMT1A) patients. In an attempt to determine the mechanisms by which the expression of this gene is regulated (with a view to lowering its expression in CMT1A patients), we subcloned genomic fragments covering 6 kb of the promoter region in an expression vector containing the β-galactosidase gene as reporter, and used these in transfection assays. We show that the 300 bp upstream of the transcription start contain the elements required for Schwann cell specific expression of the reporter gene. This minimal promoter activity appears to be under the control of a silencer element sensitive to cAMP, located between −0.3 kb and −3.5 kb from the start of transcription. Computer analysis of 2 kb of the promoter predicted the presence of transcription factor binding sites, including CREB (which may be involved in the response of PMP22 expression to cAMP stimulation) and steroid receptors. Using constructs with or without the CREB sites, we were able to demonstrate that these sites are involved in silencing the PMP22 promoter activity. Lastly, we identified a region containing blocks of polymorphic CA repeats, located close to the CREB binding site, which may further influence the transcriptional activity of PMP22.