What comes first: translational repression or mRNA degradation? The deepening mystery of microRNA function.

While many mechanisms have been proposed for microRNAs (miRNAs) function, most ultimately cause message degradation. A view has emerged that miRNAs silence gene expression by promoting the association of mRNA decay factors. Recent research results, however, suggest that in both zebrafish and fruit fly, translational inhibition is the initiating event of miRNA-mediated gene silencing.