Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
泉 雄大; 松尾 光一*; 藤井 健太郎; 横谷 明徳
no journal, ,
真核生物のDNAはH2A, H2B, H3, H4と呼ばれる4種類のヒストンタンパクそれぞれ2分子が形成するヒストンオクタマーに巻きついた状態で存在し、この構造はヌクレオソームと呼ばれる。放射線などによりDNA切断が起こると、ヒストンタンパクの一部を構成するH2AXのリン酸化が広範囲に起きることが知られている。この広範囲の変化が、ヌクレオソーム全体の構造変化を引き起こし、損傷部位に修復タンパクをリクルートする際に重要な役割を果たしていると考えられる。しかしながら、その立体構造変化の詳細に関する知見は得られていない。そこで本研究では、X線を照射した細胞から抽出したヒストンH2A/H2Bダイマーの立体構造が変化しているかどうかを、円二色性(CD)スペクトル測定により調査した。その結果、X線を照射した細胞から抽出したヒストンH2A/H2Bダイマーでは、未照射のものに比べて
-ヘリックス構造が増加していることを示すCDスペクトル変化が観測された。このことは、細胞へのX線照射によって、ヒストンH2A/H2Bダイマーの立体構造が変化し、新たに-ヘリックス構造が形成されたことを示す。
泉 雄大; 松尾 光一*; 藤井 健太郎; 横谷 明徳
no journal, ,
The conformational change in the chromatin architecture induced by the phosphorylation plays an important role in the DNA damage responses, such as recruiting DNA repair protein machineries to the damaged sites. In an attempt to study conformational change of histone dimer induced by DNA damage, we measured vacuum ultraviolet circular dichroism (VUV-CD) spectra of histone dimer extracted from X-irradiated cells. An apparent spectral difference was observed below 205 nm. The CD intensity of irradiated sample was shifted toward negative side compared with that of unirradiated sample. Comparing with standard VUV-CD spectra of protein secondary structures, namely -helix, 
-strand, turn, and unordered structure, it is expected that unordered structure relatively increased in this condition. This result shows that the conformational change of histone dimer is induced by X-ray irradiation.
泉 雄大; 藤井 健太郎; 松尾 光一*; 横谷 明徳
no journal, ,
DNA wraps around core histone proteins composed of several subunits named as H2A, H2B, H3, and H4 in eukaryotic nuclei. It has been gradually recognized that chemical modifications of histones play important roles in DNA repair processes. Recently, we observed relative increment of -helix structure of histone H2A/H2B induced by X-irradiation to human cells using circular dichroism (CD) spectroscopy. In this work, we investigated the secondary structural change of histone H3/H4 measuring vacuum ultraviolet CD (VUV-CD) spectra. The VUV-CD spectra did not show apparent difference between H3/H4 extracted from X-irradiated cells and that extracted from unirradiated cells. This result suggests that (1) the structure of H3/H4 was not altered although that of H2A/H2B was altered, or (2) opposite structural changes between H3 and H4 occurred, for example, -helix structure of H3 increased, but that of H4 decreased, since CD spectra reflect total amount of each secondary structure.
泉 雄大; 藤井 健太郎; 山本 悟史*; 松尾 光一*; 横谷 明徳
no journal, ,
DNA wraps around core histone proteins composed of several subunits named as H2A, H2B, H3, and H4 in eukaryotic nuclei. It has been gradually recognized that chemical modifications of histones play important roles in DNA repair processes. Recently, we observed relative increment of -helix structure of H2A and H2B (H2A-H2B) induced by X-ray irradiation to human cells. In this work, we investigated structural alterations of H3 and H4 (H3-H4) extracted from X-irradiated cells using vacuum ultraviolet circular dichroism (VUV-CD) spectroscopy. The VUV-CD spectral shape of H3-H4 extracted from X-irradiated cells was different from that from unirradiated cells. Analyzing the CD spectra, we found that -helix structure component of H3-H4 relatively decreased by X-irradiation to cells. This is an opposite of structural change observed in H2A-H2B. The mechanism of histone structural alterations in response to X-ray irradiation has not been identified yet, but a possible mechanism could be via post-translational modifications which are known to occur in histones during DNA damage responses. Cyclopedic VUV-CD spectroscopy of specific modified-histones to understand the alteration mechanism and its contribution to DNA repair processes is warranted for future studies.