Abundance and functional enrichment of genes targeted by many distinct miRNAs. (a) The observed number of genes targeted by many miRNAs is dramatically greater than the expected number for all three algorithms. The threshold for the number of miRNAs to be considered highly targeted is defined to be one standard deviation more than the average number of miRNAs predicted to target a gene. (b) A large proportion of genes targeted by many miRNAs are transcriptional regulators and nuclear genes, but this enrichment decreases as the number of miRNAs is reduced. Genes involved in ion transporters do not show this trend. In (b-d), asterisks denote P < 0.01. (c) Enrichment, instead of proportion (as before), is shown of transcriptional regulators and nuclear genes for highly targeted genes, with the same enrichment for highly targeted genes. The expected enrichment for a random set of genes targeted by any number of miRNAs is 1.0 (that is, no enrichment), shown by the dotted line. (d) The enrichment of transcriptional regulators and nuclear genes among highly targeted genes remains after controlling for 3' UTR length.
Hon and Zhang Genome Biology 2007 8:R166 doi:10.1186/gb-2007-8-8-r166