@misc{oai:repo.qst.go.jp:00077961,
 author = {Hasegawa, Maho and Nishikubo, Kai and Fujiwara, Satoru and Matsuo, Tatsuhito and Yokoya, Akinari and Hasegawa, Maho and Nishikubo, Kai and Fujiwara, Satoru and Matsuo, Tatsuhito and Yokoya, Akinari},
 month = {Dec},
 note = {Radiation-induced double strand break (DSB) has been known to be effeciently repaired by non-homologous end joining (NHEJ). XRCC4 is involved in this pathway as a dimer in vivo. Phosphorylated XRCC4 functions as scaffold when LigIV rejoins the DSB termini. XRCC4 might form a filamentary complex with another protein, XRCC4-like factor (XLF) [1]. The structural change of XRCC4 induced by phosphorylation may play an important role to form this higher order structure. So far, using circular dichroism (CD) method, we clarified the secondary structure of XRCC4 wild type and variant in which the serine-320 was substituted to an aspartic acid (denoted as S320D) to mimic phosphorylation. There is no significant difference of the XRCC4 dimer structures between the wild and S320D [2]. On the other hand, for the multimer, the secondary structure was different between the two proteins. In this study, we further worked on small angle X-ray scattering (SAXS) analysis and dynamic light scattering (DLS) to obtain conformational aspects. Although the obtained SAXS curve of variant was different from that of wild type, the dimer sample might contain certain amount of multimers. We have to estimate the effect of multimers in the curves, as well as improve our sample preparation. The DSL results showed similar particle diameters for those proteins. We are working on further analysis of XRCC4s with substitution of other serine sites to an aspartic acid aspartic and discuss on the XRCC4 activation mechanism.

[1]Williams, G.J. et al., DNA Repair 17, 110-120 (2014).
[2]Nishikubo, K. et al., The 23rd Hiroshima International Symposium on Synchrotron Radiation, 2019., 第3回QST国際シンポジウム「Quantum Life Science」},
 title = {Analysis of activated structure of phosphorylated XRCC4  by small angle X-ray scattering},
 year = {2019}
}