ABSTRACT
Discovery of MicroRNAs Wightman et al. (1) and Lee et al. (2) found that two genes, lin-4 and lin-14, are important in the regulation of the larval development of a nematode, Caenorhabditis elegans, and noted that lin-4 gene product represses the lin-14 gene (1). Subsequently, in 1993, it was also discovered that lin-4 does not code for a protein but codes for two short RNA transcripts, which are 22 and 61 nt (nucleotide) long (2) and that it had complementary repeated sequences to the 3′ UTR of the lin-14 mRNA (2,3). These observations led to the understanding that the transcriptional product of lin-4 targeted the lin-14 mRNA leading to translational repression (2,3). Later it became clear that this class of small (∼22 nt long) noncoding RNAs termed microRNAs (miRNA) could regulate animal and plant gene expression either by cleaving or by inhibiting the messenger RNA (mRNA) from taking part in translation.
