Requirement for flap endonuclease 1 (FEN1) to maintain genomic stability and transcriptional gene silencing in Arabidopsis

As a central component during Okazaki fragment maturation, flap endonuclease 1 (FEN1) removes the 5’ flap and maintains genomic stability. Here, FEN1 was cloned as a suppressor of transcriptional gene silencing (TGS) from a forward genetic screen. FEN1 is abundant in the root and shoot apical meristems and FEN1-GFP shows a nucleolus-localized signal in tobacco cells. Arabidopsis fen1-1 mutant is hypersensitive to MMS and shows reduced telomere length. Interestingly, genome-wide ChIP-seq and RNA-seq results demonstrate that FEN1 mutation leads to a decrease in the H3K27me3 level and an increase in the expression of a subset of genes marked with H3K27me3. Overall, these results uncover a role for FEN1 in mediating TGS besides maintaining genome stability in Arabidopsis. Overall design: To characterized the role of FEN1 in epigenetic silencing, we examine histone modification and RNA expression changes by whole-genome RNA sequencing; H3K27me3-, H3K4me3-, H3K9me2-, H3-ChIP-seq in A. thaliana transgenic wild type (TWT) and fen1 mutant