Binds to nonmethylated 5'-d(CGG)(n)-3' trinucleotide repeats in the FMR1 promoter. May play a role in regulating FMR1 promoter. Ubiquitous. Highly expressed in placenta, thymus, lymph nodes, cerebellum and cerebral cortex. Low expression in other regions of the brain. Expressed in fetal brain and kidney. Lower expression in fetal liver and lung. Binding is severely inhibited by complete or partial cytosine-specific DNA methylation of the binding motif.