miRNA interaction with its mRNA target usually results in down-regulation of that target, or translation repression. Surprisingly, in our study two miR-9 targets (TGFBR2, NOX4) were up-regulated. A recent report gives an example of a miRNA species (Let-7) switching its target expression from repression to activation dependent upon the cell cycle (Vasudevan et al., 2007). Thus, up-regulation of genes by microRNA is possible. Activation of miR-9 by alcohol might cause up-regulation of some targets and concomitant down-regulation of others.
