DNA Replication Factor C1 Mediates Genomic Stability and Transcriptional Gene Silencing inArabidopsis   

Abstract

Genetic screening identified a suppressor of ros1-1, a mutant of REPRESSOR OF SILENCING1 (ROS1; encoding a DNA demethylation protein). The suppressor is a mutation in the gene encoding the largest subunit of replication factor C (RFC1). This mutation of RFC1 reactivates the unlinked 35S-NPTII transgene, which is silenced in ros1 and also increases expression of the pericentromeric Athila retrotransposons named transcriptional silent information in a DNA methylationindependent manner. rfc1 is more sensitive than the wild type to the DNA-damaging agent methylmethane sulphonate and to the DNA inter-and intra-cross-linking agent cisplatin. The rfc1 mutant constitutively expresses the G2/M-specific cyclin CycB1;1 and other DNA repair-related genes. Treatment with DNA-damaging agents mimics the rfc1 mutation in releasing the silenced 35S-NPTII, suggesting that spontaneously induced genomic instability caused by the rfc1 mutation might partially contribute to the released transcriptional gene silencing (TGS). The frequency of somatic homologous recombination is significantly increased in the rfc1 mutant. Interestingly, ros1 mutants show increased telomere length, but rfc1 mutants show decreased telomere length and reduced expression of telomerase. Our results suggest that RFC1 helps mediate genomic stability and TGS in Arabidopsis thaliana.

The second subunit of DNA-polymerase delta is required for genomic stability and epigenetic regulation

“…of the core DNA-replication proteins, including the DNA single-strand-binding protein RPA2A (Xia et al, 2006), Pola (Liu et al, 2010a), Pol « (Yin et al, 2009), POLD2 (this study), RFC1 (Liu et al, 2010b), and TOUSLED protein kinase (Wang et al, 2007). Other studies have identified other DNA replication-related proteins involved in mediating TGS, including BRU1 (Takeda et al, 2004), chromatin assembly factor (CAF-1) subunits FAS1 and FAS2 (Ono et al, 2006;Schonrock et al, 2006), and TEBICHI (Inagaki et al, 2009).…”

“…However, pold2-1 had little effect on the ProRD29A:LUC locus in dms3-4. Like mutants of DNA replication-related proteins (Elmayan et al, 2005;Xia et al, 2006;Yin et al, 2009;Liu et al, 2010aLiu et al, , 2010b, pold2-1 failed to suppress the silenced ProRD29A:LUC in the ros1-1 mutant (Fig. 1F).…”

“…1C). TSIs are endogenous TGS loci (Steimer et al, 2000), the expression of which is altered in some mutants involved in DNA methylation, histone modification, or DNA replication (Steimer et al, 2000;Xia et al, 2006;Yin et al, 2009;Liu et al, 2010aLiu et al, , 2010b. The expression of TSIs was increased in these isolated mutants (Fig.…”

“…In Arabidopsis (Arabidopsis thaliana), mutations in replication factor C1 (RFC1), Pol «, Pol a, and replication protein A2A (RPA2A) can suppress gene silencing in a DNA methylation-independent manner (Elmayan et al, 2005;Kapoor et al, 2005;Xia et al, 2006;Liu et al, 2010aLiu et al, , 2010b. These mutants are hypersensitive to DNA damage and exhibit reduced telomere length and increased genomic instability.…”

Regulating DNA Replication in Plants

“…RFC1 is required for replication of the ssDNAcontaining wheat dwarf virus (WDV) genome to stimulate binding of the initiator Rep protein to 3 0 -OH containing DNA substrates (Luque et al 2002). Besides to its role as a clamp loader, RFC1 also contributes to transcriptional gene silencing of certain genes and transposons (Liu et al 2010b). …”