Types of miRNA regulation. Type A: MiRNA regulating gene expression. miRNAs can lead to mRNA cleavage and degradation or mRNA translational repression. Type B: MiRNA regulating target protein. The action of under or over expression of miRNAs can directly repress gene translation. Type C: MiRNA regulating on PPI networks. miRNA shows as an indirect regulator to affect dynamic PPI network stability.