Abstract: As a central component during DNA replication and DNA repair process, humanflapendonuclease-1(FEN1) plays indis-pensable roles in genome stability and integrity. AlthoughFEN1expression level is dysregulated in many types of tumor cells, mutation events ofFEN1gene are rare to be reported in the study paper. We previously detected one N266D heterozygotic mutant in the hemato-poietic cells of a leukemia patient. In this study, we successfully constructed N266D expressed plasmids, and purified FEN1-WT and N266D proteins. We also detected the nuclease activities of N266D and FEN1-WT by TAMRA tagged DNA substrates and determinedthat there was no obvious difference between them. RTCA method determined that the proliferation capacity of 293T cells was sup-pressed when overexpressed with N266D mutant. Based on our results of nuclease activities and cell proliferation capacity of N266Dmutant, it is possible to dig the potential roles of N266D mutant during tumor development in future.

Key words: FEN1, mutant, nuclease activity, cell proliferation