Figure 4. Differentially expressed motifs in PCa. (A) Twenty-four extensively enriched motifs were identified among the phosphosites, including 18 pSer and 6 pThr motifs. Percentage of foreground matches was used as the enrichment index. (B) Differentially expressed motifs between PC-3 and PC-3M cells. Seven motifs -SxxE-, -PxS-, -PxSP-, -SxxK-, -SPxK-, -SxxxxxP- and -SP-, were up-regulated in PC-3M cells. The motifs -RxxS- and - SP- were down-regulated. (Motif -SP- was enriched among both up- and down-regulated phosphosites).