Abundance of microRNA target motifs in the 3′-UTRs of 20527 human genes

A mechanism, selective avoidance, proposes that microRNA (miRNA) target sites are selectively depleted in the 3'-UTRs of genes expressed at the same time and place as a miRNA. If this mechanism is ubiquitous, the target motif occurrences in the 3'-UTRs would be decreased. To test this hypothesis, we examined miRNA target motif occurrences in the 3'- and 5'-UTRs of 20527 human protein-coding genes. The results revealed that miRNA target motifs appeared more frequently than non-target motifs and were enriched in the 3'-UTRs. This enrichment was relatively reduced in a set of 2525 genes coexpressed with miR-124a in the prefrontal cortex, but still remained at a high level, suggesting that miRNA target motifs are fostered by some other factors that surpass the influence of selective avoidance. (C) 2007 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.