The Sox2 transcription factor binds RNA

A subset of transcription factors is proposed to form functional interactions with RNA to facilitate proper regulation of gene expression. Sox2, a critical transcription factor for maintenance of pluripotency and neurogenesis, is found associated with several lncRNAs, although it is unknown whether these interactions are direct or via other proteins. We demonstrate that human Sox2 interacts directly with one of these lncRNAs with high affinity through its HMG DNA-binding domain. Furthermore, rather than interacting with a single high affinity site, Sox2 binds regions of dsRNA in a non-sequence specific fashion. RNA binding is competitive with dsDNA, yet interaction with RNA is primarily electrostatically driven using a partially overlapping set of amino acids as that used for DNA binding. Finally, we use two distinct crosslinking techniques, formaldehyde and UV, with RNA immunoprecipitation (respectively, “fRIP” and “UVRIP”) of Sox2 in mouse embryonic stem cells to identify >1000 potential Sox2-RNA interacting partners with ~75% overlap between the two techniques. Together, these data reveal that Sox2 productively binds dsRNA with affinities rivaling ChIP-validated promoter DNA sites, suggesting that the transcriptome plays a significant role in regulation of gene expression by Sox2. Overall design: The four biological replicates for both fRIP and UVRIP, a total of eight, were generated to evaluate fold change of IP relative to input.