Dimerization through the RING-Finger Domain Attenuates Excision Activity of the piggyBac Transposase.

The movement of the piggyBac transposon is mediated through its cognate transposase. The piggyBac transposase binds to the terminal repeats present at the ends of the transposon. This is followed by excision of the transposon and release of the nucleoprotein complex. The complex translocates, followed by integration of the transposon at the target site. Here, we show that the RING-finger domain (RFD) present toward the C-terminus of the transposase is vital for dimerization of this enzyme. The deletion of the RFD or the last seven residues of the RFD results in a monomeric protein that binds the terminal end of the transposon with nearly the same affinity as wild type piggyBac transposase. Surprisingly, the monomeric constructs exhibit >2-fold enhancement in the excision activity of the enzyme. Overall, our studies suggest that dimerization attenuates the excision activity of the piggyBac transposase. This attribute of the piggyBac transposase may serve to prevent excessive transposition of the piggyBac transposon that might be catastrophic for the host cell.