The Effect of Glucocorticoids on TAF1 Gene Transcription in X-linked Dystonia Parkinsonism

Abstract

Objective. X-linked Dystonia Parkinsonism (XDP) is associated with a SINE-VNTR- Alu (SVA) retrotransposon insertion in an intron of the TAF1 gene that alters gene transcription and splicing. In this study, we determined if the SVA insertion introduces glucocorticoid (GC)-responsive cis-regulatory elements that may contribute to dysregulated TAF1 transcription and XDP disease progression.

Methodology. We performed in silico analysis to identify potential GC receptor (GR) binding sites within the XDP-SVA. We also conducted promoter-reporter assays on HeLa and HEK293T cells to assess the intrinsic promoter activity of three XDP-SVA variants representing different hexameric repeat lengths associated with differences in disease onset. We treated XDP fibroblast cell models with GR agonist (CORT) or antagonist (RU486), then subjected TAF1 and the XDP-associated aberrant transcript, TAF1-32i to gene expression analysis.

Results. A transcription factor binding site search revealed three binding sites for GR within the XDP-SVA—two within the SINE region and one in the Alu region. Promoter-reporter assays showed induction of XDP-SVA promoter activity upon CORT treatment that was dependent on the cell line and XDP-SVA hexamer repeat length. Gene expression analysis showed that baseline TAF1 levels differed between control and patient fibroblast cell lines, and treatment with CORT led to an increasing trend in the expression of the aberrant TAF1-32i transcript but did not reach statistical significance. Treatment with RU486 increased TAF1 mRNA expression only in the control cell lines.

Conclusion. Using reporter assays, the XDP-SVA was shown to exhibit CORT-dependent transcriptional activation. Gene expression analysis also showed that GC signaling may influence TAF1 and TAF1-32i expression, possibly through interaction with the XDP-SVA. Our data provide a potential link between stress and XDP progression.