Remodeling of nucleosome by a DNA translocating bacterial restriction-modification enzyme
A eukaryotic cell has specialized ATP-dependent chromatin remodelers, such as SWI/SNF, to unfurl DNA from nucleosome for functional processing. The ATPase that powers the movement of the chromatin remodeler on the DNA (translocation) is evolutionarily related to those powering the translocation of the functionally distinct bacterial restriction-modification (RM) enzymes. The collision of a SWI/SNF chromatin remodeler and a nucleosome, results in sliding/ejection of the constituent histone octamer, while two converging ATP-dependent RM enzymes catalyze DNA cleavage. Here, we investigate if an ATP-dependent Type ISP RM enzyme, an active and directional translocase, can remodel nucleosomes. Our results reveal that in presence of ATP, a Type ISP RM enzyme can displace the octamers from not just mononucleosomes but also two tandem nucleosomes. However, a Type III RM enzyme, which employs a homologous ATPase as a switch to facilitate bidirectional 1D diffusion along the DNA, fails to remodel the nucleosome. This implies that an actively translocating Type ISP RM enzyme generates sufficient force for chromatin remodeling, and may serve as artificial sequence-specific chromatin remodelers.