Figure 4.

Genes without target sites for endogenous miRNAs show less dilution effects than does the complete set of potential targets. (A) The scatter plot shows the average log ratios for predicted miRNA and siRNA targets as measured by microarrays of 90 over-expression experiments (55 miRNAs and 35 siRNAs) as a function of the miRNAs' and siRNAs' total number of target sites. The line is based on a linear regression and indicates that there is a significant correlation between the total number of target sites and average log ratio (r = 0.37; P < 0.001). (B) The scatter plot shows the average log ratios for the subset of genes that have no predicted target sites for endogenous miRNAs as a function of the miRNAs' and siRNAs' total number of target sites (r = 0.22; P = 0.068). Only the 70 samples assayed in HeLa were included. In both plots, red circles represent miRNAs, and blue triangles represent siRNAs. miRNA, microRNA; siRNA, small interfering RNA.