RNA Helicases on the Move

Abstract

We have investigated the mechanical properties of the RNA-helicase-motor proteins in single-molecule assays using Magnetic Tweezers. RNA helicases are fundamental molecular motors that remodel RNA structures, DNA/RNA hybrids and RNA-protein complexes that are essential in gene regulation. So far their mechanism of action is very much debated and the classical assays are not sufficient to answer these questions this is particularly true for Dead box helicases. We have developed a cyclic assay in parallel on tens of molecules at the same time which allows detecting the unwinding of short RNA/DNA hybrids in real time by Ded1 helicase. The observation of unwinding by the Ded1 helicase in various conditions of ATP and analogs indicate that the enzyme melt the duplex rather than translocating along ssDNA and strip the complementary strand. On the contrary Upf1 helicase is a real translocase moving along nucleic acids over several hundred bases either on single strand or unwinding duplex.