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J.S. Vogel, E.C. Bullen, C.L. Teygong, E.W. Howard; Potential Alternative Promoter Usage for the RLBP1 Gene . Invest. Ophthalmol. Vis. Sci. 2006;47(13):4905.
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Retinal pigment epithelial (RPE) cells are highly differentiated, but can undergo phenotypic modulation in response to tissue damage in diseases such as proliferative vitreoretinopathy. RPE cells are characterized by their expression of genes involved in pigmentation and the retinal cycle. Our goal is to understand the molecular basis of RPE–specific gene expression, and to begin to do this, we have analyzed the promoter for the RLBP1 gene.
In order to identify primary transcripts of the RLBP1 gene, we performed 5’ RACE using cDNA from ARPE–19 cells that had a differentiated phenotype. We used this information in conjunction with a bioinformatics approach to evaluate exon usage and potential transcription start sites. We next confirmed the ability of different potential promoters to function in RPE–like cells using the D407 cell line (a kind gift from Richard Hunt, Ph.D.), which were transiently transfected with varying lengths of promoter fragments linked to luciferase reporters.
Our 5’ RACE sequencing results revealed the presence of a new exon 1 for the RLBP1 primary transcript, distinct from the previously reported first exon. This results from the presence of an alternative transcription initiation site 5’of the previously identified site, though no changes in coding sequence occur due to the inclusion of this new exon. Comparison with the mouse gene suggests the possibility that a similar situation exists in multiple species. We will present results detailing the relative ability of the two potential RLBP1 promoters to drive the expression of a reporter when transfected into D407 cells.
We have identified an alternative transcription initiation site in the RLBP1 gene that includes an alternative exon 1.
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