Base Frequency Matrix as a Function of Nucleotide Position.
The tri-nucleotide spacer sequence is conserved at ERα-bound ERE sequences. Base frequency matrix as a function of nucleotide position for 646 ERE sequences. Transcription Element Search Software (TESS) was used to analyze 1017 ERα-bound loci at two different stringencies of detection. High stringency (0–10% deviation from the consensus ERE sequence) and low stringency (10–20% deviation from the consensus ERE) results are shown in Table 1A and 1B, respectively. These data are pooled (Table 1C) to reveal a total of 646 ERE sequences residing within 509 receptor-bound loci. The distribution of ERE sequences within repetitive elements is indicated for each stringency. The tri-nucleotide spacer sequences are non-randomly distributed at all stringencies of detection (see main text) even when repetitive element EREs are excluded from the analysis (see Table S4).