Zusammenfassung
Background
Mutations in the myocilin (MYOC)/TIGR gene are responsible for autosomal-dominant juvenile primary open-angle glaucoma (POAG). In patients with non-autosomal-dominant POAG, such mutations are rare, but the expression of MYOC/TIGR in the trabecular meshwork (TM) of the eye is considerably higher than in normals. We performed transfection, DNAse I footprinting, mutagenesis and ...
Zusammenfassung
Background
Mutations in the myocilin (MYOC)/TIGR gene are responsible for autosomal-dominant juvenile primary open-angle glaucoma (POAG). In patients with non-autosomal-dominant POAG, such mutations are rare, but the expression of MYOC/TIGR in the trabecular meshwork (TM) of the eye is considerably higher than in normals. We performed transfection, DNAse I footprinting, mutagenesis and electrophoretic mobility shift assays (EMSA) to identify elements responsible for the basal transcription of MYOC/TIGR in TM cells and astrocytes.
Results
DNAse I footprinting experiments of the human MYOC/TIGR promoter showed a major protected area between nt −106 to −77, which was not conserved in the homologous region of the mouse myoc/tigr promoter. In addition, the TATA-box was protected, as well as at least three downstream sites, including an AP-1-like sequence. Deletion of the −106 to −77 region caused a substantial loss of functional promotor activity in all cell types. Site-directed mutagenesis and EMSA experiments revealed the presence of two regulatory elements in the −106 to −77 region. Each of these cis-elements is essential for minimal promoter activity. The 5′-half of the region contains a sequence with similarities to NF-κB-related sites, however, binding of NF-κB could not be confirmed by EMSA. The 3′-half contains a canonical E-box sequence. EMSA experiments showed that the upstream regulatory factor (USF) was binding to the E-box sequence and that the binding can be supershifted by specific antibodies.
Conclusions
Several DNA-protein binding elements contribute to a transcription of MYOC/TIGR, and USF is critically required for its basal transcription in trabecular meshwork cells and astrocytes.
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