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

Abstract

SUMMARY As a central component in the maturation of Okazaki fragments, 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. The Arabidopsis fen1-1 mutant is hypersensitive to methyl methanesulfonate and shows reduced telomere length. Interestingly, genome-wide chromatin immunoprecipitation and RNA sequencing results demonstrate that FEN1 mutation leads to a decrease in the level of H3K27me3 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 as well as maintaining genome stability in Arabidopsis.

APURINIC/APYRIMIDINIC ENDONUCLEASE2 and ZINC FINGER DNA 3′-PHOSPHOESTERASE Play Overlapping Roles in the Maintenance of Epigenome and Genome Stability

“…These results indicate that ZDP and APE2, two BER proteins, play overlapping roles in the maintenance of nuclear genome stability. Similar constitutive activation of the DDR was found in plants with mutations in proteins involved in DNA repair, including ASYMMETRIC LEAVES1/2 ENHANCER7 (Luo et al, 2012), the largest subunit of replication factor C (RFC1) (Liu et al, 2010b), POLα/ICU2, a catalytic subunit of DNA polymerase α (Liu et al, 2010a), POLD2, the second small subunit of DNA polymerase δ (Zhang et al, 2016b), ABO4/ POL2a/TIL1, a catalytic subunit of DNA polymerase ε (Yin et al, 2009), and FLAP ENDONUCLEASE1 (Zhang et al, 2016a). The strong similarity in the effects of mutating these DNA repair proteins and those produced by mutating ZDP and APE2 suggest that these proteins may function in the same pathway.…”

DNA polymerase epsilon is a central coordinator of heterochromatin structure and function in Arabidopsis

“…Several studies reported TE silencing defects in replisome-related mutants and in plants treated with DNA-damaging agents, where replication is expectedly disturbed (5,(13)(14)(15)(16)(17)(18)(19)(20). We show that HU can alleviate TE silencing but does not enhance pol2a-induced release of silencing (fig 6G), which points to replicative stress as a cause of loss of TE silencing in pol2a mutants.…”

“…Mutations in several DNA replication-related genes have been reported to destabilize silencing of transgenes and selected endogenous loci in Arabidopsis. These mutations include mutations in the replication protein A2A (RPA2A), the DNA replication factor C1 (RFC1), the flap endonuclease 1 (FEN1), the topoisomerase VI subunit MIDGET, the FAS1 and FAS2 components of the Chromatin assembly factor 1 (CAF-1), as well as mutations in subunits of the three replicative DNA polymerases (Pol), Pol alpha (α), delta (δ) and epsilon (ε) (13)(14)(15)(16)(17)(18)(19)(20)(21).…”

“…Interfering with DNA replication would be expected to lead to improper propagation of epigenetic patterns, however evidence for components linking DNA replication with epigenetic inheritance is scarce. None of the corresponding mutants harbor reduced DNA methylation levels (13,14,(16)(17)(18)(19)(20)22), and although decreased levels of H3K9me2 at desilenced loci were reported in Pol α mutants, the depletion in this mark was surprisingly not associated with detectable changes in DNA methylation (14). Many of these mutants show reduced level of H3K27me3 at upregulated genes (16,17,(23)(24)(25), but this cannot explain release of heterochromatic TE silencing since H3K27me3 is largely excluded from constitutive heterochromatin (26).…”

Identification of novel genetic factors underlying the host-pathogen interaction between barley (Hordeum vulgare L.) and powdery mildew (Blumeria graminis f. sp. hordei)

“…Particularly, the XPG (Xeroderma Pigmentosum Complementation Group G) N-terminal domain and the XPG Internal-region seem to be conserved ( S4A Fig). In Arabidopsis, FEN1 is essential for genome stability, development, and transcriptional gene silencing [101,102]. Nevertheless, FEN1-B proteins seem to fulfill distinct functions besides their regulatory role in cell proliferation [61].…”