MIGRATION OF A HOLLIDAY JUNCTION THROUGH A NUCLEOSOME DIRECTED BY THEESCHERICHIA-COLI RUVAB MOTOR PROTEIN

Chromatin plays a critical role in regulating access to DNA by protein s that direct recombination and repair. The E. coli RuvAB protein comp lex promotes branch migration of the Holliday junction recombination i ntermediate. The ability of RuvAB to negotiate passage of the junction through nucleosomal DNA is examined. The model system involves the fo rmation of a Holliday junction positioned upstream of a nucleosome. Un assisted, the junction is blocked by a histone octamer. In the presenc e of RuvAB and ATF, rapid branch migration through the nucleosome is o bserved. It results in disruption of the histone-DNA interactions lead ing to the removal of the octamer from the junction intermediate. Thes e results suggest that eukaryotic DNA motor proteins analogous to RuvA B could function during recombination to promote branch migration thro ugh chromatin.