R-loops Associated with Triplet Repeat Expansions Promote Gene Silencing in Friedreich Ataxia and Fragile X Syndrome
Figure 7
Model for the role of R-loops in mediating FXN and FMR1 gene silencing.
Background R-loop level on wild type allele allows efficient transcriptional elongation and gene expression. Transcribed (GAA)n and (CGG)n expanded repeats form R-loops resulting in decreased initiation and elongation of RNA Pol II. This leads to downregulation of FXN and FMR1 expression, associated with formation of repressive DNA and chromatin marks.