Direct visualization of RecQ helicase-DNA interaction with fluorescence microscopy and atomic force microscopy

RecQ helicase-DNA interactions were directly visualized with fluorescence microscopy. DNA-RecQ complexes formed in binding and unwinding reaction were stretched onto the hydrophobic surface by molecular combing method. The complexes can be observed with fluorescence microscope because the DNA molecules were labeled with dye molecules of YOYO-1. The DNA binding and unwinding activity of RecQ helicase leads to reduced lengths of the observed DNA molecules. More direct observations with atomic force microscopy were also made. It was seen that RecQ is mainly monomeric both in solution and after binding to DNA.