Figure 1.

Representative examples of subclasses of SP promoters. Histograms show the fraction of tags that map into the 120 bp region centered on the TC. TC identifiers are shown above each histogram. Three subclasses of the SP TCs defined by Carninci and coworkers [8] were analyzed: (a) single-TSS promoters having a single well defined TSS; (b) shallow-TSS promoters, which is the subset of single TSS promoters that have one sharp peak surrounded by multiple weakly defined TSSs; and (c) twin-TSS classed promoters, which are characterized by two closely located, well defined TSSs, and in turn can be classified by the number of base pairs in between them (0-3 bp spacing). bp, base pair; SP, single peak; TC, tag cluster; TSS, transcription start site.