Distribution of MotifMap regulatory elements as a function of conservation. Empirical distribution of distances of human transcription factor binding sites to the closest (≤ 10 Kbp and ≤ 50 Kbp) RefSeq gene transcription start site (TSS). The sites are grouped into quartiles according to the BBLS score; each group has one quarter of the total binding sites. The BBLS range for each quartile is given at the top of each plot. As the BBLS conservation score increases, we observe a larger proportion of binding sites close to the TSS of the closest gene.