Background correction removes misleading enrichment of HuR binding in region downstream of transcription start sites. Reads from each library were normalized for number of nucleotides per library and length of region (fraction of nucleotides per library per Kb). Background reads were derived from union of all three backgrounds. Numbers 5+, 10+ and 25+ indicate HuR clusters with 5, 10, or 25 or more reads, per cluster. Regions 25-50 bp downstream of transcription start sites (green bars) and 50-100 bp downstream (purple bars) appear enriched prior to background correction; however, they were no longer enriched after correction.