Coverage of protein-coding genes by E2F HCTs. The coverage profile reveals a clear peak with a symmetric distribution around the transcription start site (TSS). Gene features are represented proportional to the median values of all human protein coding genes: 5′ UTR, 181 nt; first coding exon, 124; first intron, 2682; internal coding exon, 123 (multiple internal exons, as well as introns, are pooled together); internal intron, 1419; last coding exon, 149; 3′ UTR, 751. The promoter region is considered to be 1.5 kb in all cases. Depending on the length of the various gene features at a particular locus, HCTs could occasionally reach internal introns and exons. In the case of genes with split 5′ UTR regions, the first intron is likely to be covered by a promoter-based HCT, resulting, as in this case, in a higher coverage relative to the first coding exon.
