MiRNAs are small non-coding RNAs~22 nucleotides (nt) long involved in the negative post-transcriptional gene regulation via RNA interference mechanism [5, 6] . The sequences of miRNAs are highly conserved among plants-microorganisms-animals, suggesting that miRNAs represent a relatively old and important regulatory pathway [7] . MiRNAs belong to the most abundant class of human gene regulators [8] : up to a third of the human genes are regulated by miRNAs [9] . MiRNAs are, therefore, key regulators of numerous genes in biological processes ranging from developmental timing to apoptosis [e.g. [10] [11] [12] [13] [14] ]. It has been speculated that miRNAs may be associated with the regulation of almost every aspect of cell physiology [8] .