FIGURE 7.

The distribution of PTB motifs in endogenous PTB pre-mRNA targets. A set of exons regulated by PTB in HeLa cells was obtained from the literature (Spellman et al. 2007) . Motifs A–D were annotated in the intronic and exonic regions around PTB regulated splice sites. The number of sites found around splice sites that were targets of PTB regulation was compared to the number of sites found around randomly selected splice sites. A sampling strategy was utilized to make this comparison. Control data sets were constructed by drawing randomly selected pre-mRNA regions from refseq pre-mRNAs such that each control set was equal in number and size and arrangement (exonic and intronic portions) to the PTB regulated set. (A) Histogram bars record the fold over-representation of each motif to the average counted in the 1000 control sets. (B) Pairs of motifs were searched with a 30-nt window as in Figure 6B. A heat map conveys the over-representation of each combination in the PTB targets relative to the average tallied over 1000 control sets.