Enrichment of transcription factor binding at expressed Alu elements reveals the potential to function as cell-type–specific enhancers. (A) The left heatmap shows the fold changes of TF ChIP-seq signals in the ±500-bp window centered on the TSSs of Alu elements specifically expressed in K562 cells compared with Alu elements expressed in other biosamples. Each row is a TF, and all 275 TFs with ChIP-seq data in K562 are included in the heatmap and sorted by their fold changes. The top left heatmaps indicate the TFs with enriched signals and motifs, with the motif logos shown at top right. (B) crisprQTL data (Gasperini et al. 2019) showed that two Alu elements expressed in K562 functioned as enhancers with significant regulatory effects on the expression of nearby genes.
