How is the genome integrity of the hyperthermophiles protected and propagated?

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Proteins and enzymes involved in DNA replication and repair in the hyperthermophilic archaea, Thermococcus kodakarensis and Pyrococcus furious were characterized by both biochemical and genetical techniques. There are three Mcm and two PCNA in T. kodakarensis, and to understand the functional sharing, we characterized the purified Mcm and PCNA proteins. In addition, we isolated amutant T. kodakarensis strains, in which one of these genes wa knocked out, and characterized their phenotypes. We found that Mcm3 and PCNA1 are essential for the viability of T. kodakarensis. Exact functions of Mcm1, Mcm2, and PCNA2 remain to be elucidated. We searched for enzymes involved in the damaged base repair system in the hyperthermophilic archaea. We identified a novel endonuclease, which cleaves at 5'-side of the damaged nucleotide, hypoxanthine, uracil, xanthine, and AP site in the DNA strand. We designated it Endonuclease Q and applied for a patent as a novel substance from Kyushu University.