BORIS binds directly to RNA in a nucleotide-specific manner. (A) SDS-PAGE western blot analysis of the purification of Halo tagged BORIS from transfected HEK293T cells. (B) In vitro binding assay using biotinylated RNA and DNA homopolymers and purified recombinant BORIS from (A). BORIS showed association with poly(rG) and poly(rU), but not with poly(rA) or poly(rC). BORIS also showed specific affinity for poly(dT), poly(dG) and poly(dC) DNA while no binding was observed to poly(dA) or the streptavidin beads alone (No oligo, lane 1). (C) Venn diagram showing the number of identified BORIS associated transcripts in hNP1 and hNP1 cells differentiated to neurons over 6 days (6dN) as well as the number of transcripts associated with BORIS in both cell types. RT-qPCR confirmation of BORIS associated transcripts in hNP1 (D) and 6dN cells (E). Data in (D) and (E) represent 2 technical replicates ± SD.