microRNAs are a class of small RNA molecules that regulate gene expression at post- transcriptional level. Concurrently, miRNA activity can also be controlled by a newly discovered regulatory mechanism called “endogenous target mimicry (eTM)” which are alternatively described as miRNA decoys or sponges. It is known that the perfect pairing at the 5' end 9th to 11th positions of miRNAs with their targets are most important for the effective cleave of targets by miRNAs. In target mimicry, eTMs bind to miRNAs with a 3 nucleotide bulge between the 5' end 10th and 11th positions via sequence complementarity. This pairing breaks the cleavage effect of miRNA on its target mimic. Thus eTMs function as ‘miRNA inhibitors’, which lead to increased expression of the miRNA target mRNAs. This novel gene regulation network plays vital roles in a wide range of biological processes. Along with endogenous target mimics, engineered artificial RNAs can produce target mimicry effects.
PeTMbase aims to provide a resource for endogenous miRNA target mimics for plants. This is a searchable database with 2728 eTM sequences predicted computationally from 11 different plant species. The number of deposited eTM records will increase as the new species are dissected for target mimicry. All sequences are available for download.