High-throughput sequencing coupled with chromatin immunoprecipitation (ChIP-Seq) peaks from multiple transcription factors form clusters within the genome. Number of ChIP-Seq peak clusters compared to the number of clusters produced after a random shuffle of peak positions for K562 (A) and (B) and Gm12878 (D) and (E). The maximum numbers of peaks found in the peak clusters were 17 for K562 and 18 for Gm12878 compared to 7 and 6, respectively, for the random shuffle. (C) and (F) show average cluster lengths in kilobase pairs with increasing numbers of peaks in the clusters. A smaller increase in peak lengths is observed for the peak clusters, indicating a higher degree of clustering. TF, transcription factor.