A Preliminary Study On Fission Yeast Dnt1Participating In DNA Damage And Repair

DNA double-strand breaks is a main formation of DNA damage. DNA damage not only are generated in the euchromatic region, but also in the heterochromatin region, such as telomere domain and rDNA regions.The early results of our lab demonstrated the nucleolar protein Dntl in fission yeast had relation to rDNA regions.The dnt1Δ mutant reduced the rDNA silencing and increased the rDNA recombination rates using the ura4+regarded as the reportor gene of rDNA repeat units. As such a large and repetitive locus, it’s thought to be unstable, unequal recombination events occurring. However, cells have evolved mechanisms to protect the stability and integrity of rDNA.In this paper, We wonder that how does Dntl participate in the DNA damage that were caused under the stress of DNA damage reagents using the genetic methods. Our results showed that Dntl is important during a perturbed S-phase in S.pombe. As is known to all, as soon as the damaged DNA were produced, the cells induced DNA damage response to cope with these assaults, but the reactions required lots of proteins, which including replication fork-associated proteins, DNA maintenance checkpoint proteins, homologous recombination proteins and G2/M regulation proteins.Swil and Swi3form the replication fork protection complex, which were the most important proteins of replication fork-associated proteins. As shown in our drop test, the Dntl and FPC do not function exclusively together. DNA damages were firstly responded with the DNA maintenance checkpoint proteins, which are made of the DNA replication checkpoints and DNA damage checkpoints. We constructed the double mutant strains between dntlA and components of the DNA replication checkpoints and DNA damage checkpoints proteins. In our genetic analysis, there are some functions between Dntl and Radl, Rad3, Crb2, Chkl, Cds1, but no genetic interactions with Rad26. Fortunately, The genetic results that dnt1Δ could rescue the rad17Δ sensitivity in response to different DNA-damaging agents suggesting that Dntl negative regulation Rad17. The damaged DNA were mainly repaired by homologous recombination and non-homologous end joining. We found that Dntl’s functions are independent to HR and NHEJ repair pathway at least in response to these DNA-damaging agents. Besides, we had explored the genetic relationships between Dntl and Smc5-Smc6complex, and DNA polymerase δ and ζ et.cl, and observed that they could no genetic connections.In addition to, we discovered that the silencing represent diverse levels however different regions of rDNA is integrated with the ura4+in forward or reverse directions. We also found that the locus of Dntl were not influenced by the reb1Δ, which associated with the RFB sites of rDNA regions. But, the reb1Δ could rescue the dnt1Δ sensitivity on these DNA-damaging agents. Sap1, which also was relative to rDNA’s RFB. The sap1-48ts dnt1Δ mutants showed a severe growth defect compare to the parent’s mutant. Besides, the Dntl locations were not affected by the sap1-48ts mutant, in contrast, the locus of Sap1were influenced by the Dntl.