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Ushigome, Takeshi*; Shikazono, Naoya; Fujii, Kentaro; Watanabe, Ritsuko; Suzuki, Masao*; Tsuruoka, Chizuru*; Tauchi, Hiroshi*; Yokoya, Akinari
Radiation Research, 177(5), p.614 - 627, 2012/05
Times Cited Count：23 Percentile：68.76(Biology)The yield of DNA damage produced in fully hydrated plasmid DNA films has been investigated to determine the linear energy transfer (LET) dependence of damage induction. The yield of single strand breaks (SSBs) with increasing LET levels of He, C and Ne ions. On the other hand, the yields of prompt double strand breaks (DSBs) increased with increasing LET. SSBs were additionally induced by treatment with base excision repair proteins, glycosylases, indicating that base lesions are produced in the hydrated DNA. This result shows that nucleobase lesions are produced via both chemical reactions with diffusible water radicals and direct energy deposition onto DNA or the hydrated layer. The yield of SSBs or DSBs observed by enzymatic treatment notably decreased with increasing LET. These results indicated that higher LET ions preferentially produce a complex type of damage that might compromise the activities of the proteins used in this study.
Yokoya, Akinari; Shikazono, Naoya; Fujii, Kentaro; Ushigome, Takeshi*; Suzuki, Masao*; Urushibara, Ayumi; Watanabe, Ritsuko
Proceedings of the 27th Symposium on Materials Science and Engineering, Research Center of Ion Beam Technology Hosei University, 8 Pages, 2008/12
It has been indicated that ion particle irradiation to living cells causes a clustered DNA damage site, defined as two or more lesions formed within a few nano meters, in a cell nuclei. The clustered damage is less readily repaired by enzymatic repair system so that it induces biological effects, such as mutation induction. We have studied the mechanism of clustered damage induction by biochemical approaches using closed circular plasmid DNA as a model molecule to be irradiated with He ions from TIARA. We have used base excision repair proteins as enzymatic probes to quantify base lesions. We have also applied a novel method using DNA denaturation to visualize multiple single strand breaks which hardly be detected by conventional method. Our recent results will be reported in this seminar.
Yokoya, Akinari; Fujii, Kentaro; Ushigome, Takeshi; Shikazono, Naoya; Urushibara, Ayumi; Watanabe, Ritsuko
Radiation Protection Dosimetry, 122(1-4), p.86 - 88, 2006/12
Times Cited Count：11 Percentile：60.27(Environmental Sciences)We have studied yields of DNA damages induced by soft X-rays obtained from a conventional soft X-ray machine in a LET region between 
-rays and ultrasoft X-rays. Practically soft X-rays with a broad energy spectrum emitted from a target of heavy metal, such as tungsten, have been widely used not only for radiobiological experiments but also for medical application such as mammography. Radiation weighting factors for these soft X-rays have been assigned to be 1 by ICRP. However, the fraction of a large number of low energy photons in the spectrum (below several tens keV) provided by bremsstrahlung is expected to be more effective for DNA damage induction than -rays since low energy photo- and Auger electrons predominantly ejected in consequence of a photoelectric effect can produce dense clusters of ionization/excitation on DNA molecules. We have examined the yield of DNA strand breaks induced by white soft X-rays (150 kVp, tungsten target). Yields of base lesions revealed by base excision repair enzymes will be also presented.
Urushibara, Ayumi; Ushigome, Takeshi; Shikazono, Naoya; Fujii, Kentaro; Tauchi, Hiroshi*; Yokoya, Akinari
no journal, ,
no abstracts in English
Yokoya, Akinari; Ushigome, Takeshi; Shikazono, Naoya; Fujii, Kentaro; Urushibara, Ayumi; Suzuki, Masao*; Tauchi, Hiroshi*; Watanabe, Ritsuko
no journal, ,
The yields of single- and double-strand breaks (SSB and DSB), base lesions and clustered damage induced in DNA were measured after exposing to various kinds of radiation. To focus on the effect of direct energy deposition from radiation track, we prepared hydrated DNA as well as solution sample with various scavenging capacities. Base excision repair enzymes, EndoIII and Fpg, were used to detect oxidative base lesions. The obtained results show that (1) the yield of directly induced SSB by the soft X-irradiation is about 30 percent of total SSBs in a cell mimetic condition and (2) the SSB yield does not significantly depend on the quality of radiation. On the other hand, (3) the yields of base lesions show a maximum by soft X-irradiation and drastically decreases with increasing of LET. (4) Soft X-rays are more effective in inducing base lesions than ions with similar LET, and (5) EndoIII treatment gives significantly higher SSB yield than those by Fpg treatment.
Yokoya, Akinari; Ushigome, Takeshi*; Tauchi, Hiroshi*; Suzuki, Masao*; Tsuruoka, Chizuru*; Noguchi, Miho; Fujii, Kentaro; Shikazono, Naoya; Watanabe, Ritsuko
no journal, ,
In order to clarify the characteristics of DNA damage induced by high LET radiation, the yields of strand breaks and base lesions induced in closed-circular plasmid DNA (pUC18) were measured after exposing to various kinds of radiation (He, Ne and C ions; 2 to 900 keV/
m). Base excision repair enzymes were used to detect oxidative base lesions. The obtained results show that (1) the yield of prompt SSBs does not depend significantly on the LET, (2) whereas the yield of DSBs increases with increasing LET, (3) The yields of isolated nucleobase lesions detected by enzymes decrease drastically with increasing LET and (4) C and Ne ions induce less base lesions than He ions when compared in the same LET region. These results indicate that the yield of cluster of nucleobase lesions, which are less readily processed by the base excision repair proteins, depends not only LET but also ion species irradiated.
