Human Replication Factor C Stimulates Flap Endonuclease 1*
Journal - Journal of Biological Chemistry
Flap endonuclease 1 (FEN1) is the enzyme responsible for specificallyremoving the flap structure produced during DNA replication,repair, and recombination. Here we report that the human replicationfactor C (RFC) complex stimulates the nuclease activity of humanFEN1 in an ATP-independent manner. Although proliferating cellnuclear antigen is also known to stimulate FEN1, less RFC wasrequired for comparable FEN1 stimulation. Kinetic analyses indicatethat the mechanism by which RFC stimulates FEN1 is distinctfrom that by proliferating cell nuclear antigen. Heat-denaturedRFC or its subunit retained, fully or partially, the abilityto stimulate FEN1. Via systematic deletion analyses, we havedefined three specific regions of RFC4 capable of stimulatingFEN1. The region of RFC4 with the highest activity spans aminoacids 170–194 and contains RFC box VII. Four amino acidresidues (i.e. Tyr-182, Glu-188, Pro-189, and Ser-192) are especiallyimportant for FEN1 stimulatory activity. Thus, RFC, via severalstimulatory motifs per molecule, potently activates FEN1. Thisfunction makes RFC a critical partner with FEN1 for the processingof eukaryotic Okazaki fragments.* This work was supported by Korea Science and Engineering Foundationgrants funded by the Ministry of Education, Science and Technology.