Comparison of the ability of CLIP and iCLIP to identify clustered YCAY motifs. (a) The enrichment of the YCAY motif around cross-link sites starting at each position relative to cross-link sites identified by re-defined CLIP cDNA deletions and iCLIP cDNA truncations. Both peaked at position +1, where the enrichment factor was 29 for CLIP cDNA deletions and 5.6 for iCLIP cDNA truncations. The dashed line shows two-fold enrichment of the YCAY motif compared to background. (b) The proportion of cross-link sites with YCAY score greater than or equal to the value shown on the x-axis.