A research group led by Professor Hitoshi Kurumizaka of the Waseda University Faculty of Science and Engineering (Department of Electrical Engineering and Bioscience) succeeded in elucidating for the first time in the world the instability of, and the structural basis of the nucleosome containing a testis-specific histone variant, human H3T, which is vital to spermatogenesis.
The findings from this research may uncover the causes of spermatogenesis impairment, which is regarded as a major factor of male infertility; thus, contributing to the advancement of reproductive medicine.
The research results, in the paper entitled "Structural basis of instability of the nucleosome containing a testis-specific histone variant, human H3T", appeared online in the Proceedings of the National Academy of Sciences of the United States of America (PNAS). (Visit the following website for abstract: http://www.pnas.org/content/early/2010/05/18/1003064107.abstract)
Structural basis of instability of the nucleosome containing a testis-specific histone variant, human H3T
Hiroaki Tachiwana1, Wataru Kagawa (1), Akihisa Osakabe (1), Koichiro Kawaguchi(1), Tatsuya Shiga(1), Yoko Hayashi-Takanaka(2), Hiroshi Kimura(2), and Hitoshi Kurumizaka(1)*
(1) Laboratory of Structural Biology, Graduate School of Advanced Science and Engineering, Waseda University, 2-2 Wakamatsu-cho, Shinjuku-ku, Tokyo 162-8480, Japan.
(2) Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamada-oka, Suita, Osaka 565-0871, Japan.
*Correspondence and requests for materials should be addressed to:
Hitoshi Kurumizaka, Graduate School of Advanced Science and Engineering, Waseda University, 2-2 Wakamatsu-cho, Shinjuku-ku, Tokyo 162-8480, Japan, URL: http://www.kurumizaka.sci.waseda.ac.jp/
Abstract
A histone H3 variant, H3T, is highly expressed in the testis, suggesting that it may play an important role in the chromatin reorganization required for meiosis and/or spermatogenesis. In the present study, we found that the nucleosome containing human H3T is significantly unstable both in vitro and in vivo, as compared to the conventional nucleosome containing H3.1. The crystal structure of the H3T nucleosome revealed structural differences in the H3T regions on both ends of the central α2 helix, as compared to those of H3.1. The H3T-specific residues (Met71 and Val111) are the source of the structural differences observed between H3T and H3.1. A mutational analysis revealed that these residues are responsible for the reduced stability of the H3T-containing nucleosome. These physical and structural properties of the H3T-containing nucleosome may provide the basis of chromatin reorganization during spermatogenesis.
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