キーワード：DNA複製, DNA修復, 試験管内系, 染色体, ツメガエル
|高橋 達郎（たかはし たつろう）||データ更新日：2020.01.17|
|1.||Riki Terui, Koji Nagao, Yoshitaka Kawasoe, Kanae Taki, Torahiko L. Higashi, Seiji Tanaka, Takuro Nakagawa, Chikashi Obuse, Hisao Masukata, Tatsuro S. Takahashi, Nucleosomes around a mismatched base pair are excluded via an Msh2-dependent reaction with the aid of SNF2 family ATPase Smarcad1., Genes & development, 10.1101/gad.310995.117, 32, 806-821, 2018.06, Post-replicative correction of replication errors by the mismatch repair (MMR) system is critical for suppression of mutations. Although the MMR system may need to handle nucleosomes at the site of chromatin replication, how MMR occurs in the chromatin environment remains unclear. Here, we show that nucleosomes are excluded from a >1-kb region surrounding a mismatched base pair in Xenopus egg extracts. The exclusion was dependent on the Msh2-Msh6 mismatch recognition complex but not the Mlh1-containing MutL homologs and counteracts both the HIRA- and CAF-1 (chromatin assembly factor 1)-mediated chromatin assembly pathways. We further found that the Smarcad1 chromatin remodeling ATPase is recruited to mismatch-carrying DNA in an Msh2-dependent but Mlh1-independent manner to assist nucleosome exclusion and that Smarcad1 facilitates the repair of mismatches when nucleosomes are preassembled on DNA. In budding yeast, deletion of FUN30, the homolog of Smarcad1, showed a synergistic increase of spontaneous mutations in combination with MSH6 or MSH3 deletion but no significant increase with MSH2 deletion. Genetic analyses also suggested that the function of Fun30 in MMR is to counteract CAF-1. Our study uncovers that the eukaryotic MMR system has an ability to exclude local nucleosomes and identifies Smarcad1/Fun30 as an accessory factor for the MMR reaction..|
|2.||Yoshitaka Kawasoe, Toshiki Tsurimoto, Takuro Nakagawa, Hisao Masukata, Tatsuro Takahashi, MutSα maintains the mismatch repair capability by inhibiting PCNA unloading, eLife, 10.7554/eLife.15155, 5, 2016JULY, 2016.07, [URL], Eukaryotic mismatch repair (MMR) utilizes single-strand breaks as signals to target the strand to be repaired. DNA-bound PCNA is also presumed to direct MMR. The MMR capability must be limited to a post-replicative temporal window during which the signals are available. However, both identity of the signal(s) involved in the retention of this temporal window and the mechanism that maintains the MMR capability after DNA synthesis remain unclear. Using Xenopus egg extracts, we discovered a mechanism that ensures long-term retention of the MMR capability. We show that DNA-bound PCNA induces strand-specific MMR in the absence of strand discontinuities. Strikingly, MutSα inhibited PCNA unloading through its PCNA-interacting motif, thereby extending significantly the temporal window permissive to strand-specific MMR. Our data identify DNA-bound PCNA as the signal that enables strand discrimination after the disappearance of strand discontinuities, and uncover a novel role of MutSα in the retention of the post-replicative MMR capability..|
|3.||Torahiko L. Higashi, Megumi Ikeda, Hiroshi Tanaka, Takuro Nakagawa, Masashige Bando, Katsuhiko Shirahige, Yumiko Kubota, Haruhiko Takisawa, Hisao Masukata, Tatsuro Takahashi, The prereplication complex recruits XEco2 to chromatin to promote cohesin acetylation in Xenopus egg extracts, Current Biology, 10.1016/j.cub.2012.04.013, 22, 11, 977-988, 2012.06, [URL], Background: Sister chromatids are held together by the ring-shaped cohesin complex, which is loaded onto chromosomes before DNA replication. Cohesion between sister chromosomes is established during DNA replication, and it requires acetylation of the Smc3 subunit of cohesin by evolutionally conserved cohesin acetyltransferases (CoATs). However, how CoATs are recruited to chromatin and how cohesin acetylation is regulated remain unclear. Results: We found that cohesin acetylation requires pre-RC-dependent chromatin loading of cohesin, but surprisingly, it is independent of DNA synthesis in Xenopus egg extracts. Immunodepletion experiments revealed that XEco2 is the CoAT responsible for Smc3 acetylation and sister chromatid cohesion. Recruitment of XEco2 onto chromatin was dependent on pre-RC assembly but was independent of cohesin loading and DNA synthesis. Two short N-terminal motifs, PBM-A and PBM-B, which are conserved among vertebrate Esco2/XEco2 homologs, were collectively essential for pre-RC-dependent chromatin association of XEco2, cohesin acetylation, and subsequent sister chromatid cohesion. The conserved PCNA-interacting protein box in XEco2 was largely dispensable for Smc3 acetylation but was partially required for cohesion. Interaction of acetylated cohesin with DNA was stabilized against salt-wash treatments after DNA replication. Conclusions: Our results demonstrate that pre-RC formation regulates chromatin association of XEco2 in Xenopus egg extracts. We propose that this reaction is critical to acetylate cohesin, whose DNA binding is subsequently stabilized by DNA replication..|
|4.||Tatsuro Takahashi, Abhijit Basu, Vladimir Bermudez, Jerard Hurwitz, Johannes C. Walter, Cdc7-Drf1 kinase links chromosome cohesion to the initiation of DNA replication in Xenopus egg extracts, Genes and Development, 10.1101/gad.1683308, 22, 14, 1894-1905, 2008.07, [URL], To establish functional cohesion between replicated sister chromatids, cohesin is recruited to chromatin before S phase. Cohesin is loaded onto chromosomes in the G1 phase by the Scc2-Scc4 complex, but little is known about how Scc2-Scc4 itself is recruited to chromatin. Using Xenopus egg extracts as a vertebrate model system, we showed previously that the chromatin association of Scc2 and cohesin is dependent on the prior establishment of prereplication complexes (pre-RCs) at origins of replication. Here, we report that Scc2-Scc4 exists in a stable complex with the Cdc7-Drf1 protein kinase (DDK), which is known to bind pre-RCs and activate them for DNA replication. Immunodepletion of DDK from Xenopus egg extracts impairs chromatin association of Scc2-Scc4, a defect that is reversed by wild-type, but not catalytically inactive DDK. A complex of Scc4 and the N terminus of Scc2 is sufficient for chromatin loading of Scc2-Scc4, but not for cohesin recruitment. These results show that DDK is required to tether Scc2-Scc4 to pre-RCs, and they underscore the intimate link between early steps in DNA replication and cohesion..|
|5.||Tatsuro Takahashi, Johannes C. Walter, Cdc7-Drf1 is a developmentally regulated protein kinase required for the initiation of vertebrate DNA replication, Genes and Development, 10.1101/gad.1339805, 19, 19, 2295-2300, 2005.10, [URL], Cdc7, a protein kinase required for the initiation of eukaryotic DNA replication, is activated by a regulatory subunit, Dbf4. A second activator of Cdc7 called Drf1 exists in vertebrates, but its function is unknown. Here, we report that in Xenopus egg extracts, Cdc7-Drf1 is far more abundant than Cdc7-Dbf4, and removal of Drf1 but not Dbf4 severely inhibits phosphorylation of Mcm4 and DNA replication. After gastrulation, when the cell cycle acquires somatic characteristics, Drf1 levels decline sharply and Cdc7-Dbf4 becomes the more abundant kinase. These results identify Drf1 as a developmentally regulated, essential activator of Cdc7 in Xenopus..|
|6.||Tatsuro Takahashi, Pannyun Yiu, Michael F. Chou, Steven Gygi, Johannes C. Walter, Recruitment of Xenopus Scc2 and cohesin to chromatin requires the pre-replication complex, Nature Cell Biology, 10.1038/ncb1177, 6, 10, 991-996, 2004.10, [URL], Cohesin is a multi-subunit, ring-shaped protein complex that holds sister chromatids together from the time of their synthesis in S phase until they are segregated in anaphase. In yeast, the loading of cohesin onto chromosomes requires the Scc2 protein. In vertebrates, cohesins first bind to chromosomes as cells exit mitosis, but the mechanism is unknown. Concurrent with cohesin binding, pre-replication complexes (pre-RCs) are assembled at origins of DNA replication through the sequential loading of the initiation factors ORC, Cdc6, Cdt1 and MCM2-7 (the 'licensing' reaction). In S phase, the protein kinase Cdk2 activates pre-RCs, causing origin unwinding and DNA replication. Here, we use Xenopus egg extracts to show that the recruitment of cohesins to chromosomes requires fully licensed chromatin and is dependent on ORC, Cdc6, Cdt1 and MCM2-7, but is independent of Cdk2. We further show that Xenopus Scc2 is required for cohesin loading and that binding of XScc2 to chromatin is MCM2-7 dependent. Our results define a novel pre-RC-dependent pathway for cohesin recruitment to chromosomes in a vertebrate model system..|
主要総説, 論評, 解説, 書評, 報告書等
2019.06.13～2019.06.14, 国立遺伝学研究所・研究集会「染色体安定維持研究会」, ミーティングオーガナイザー.
2017.12.06～2017.12.09, 2017年度生命科学系学会合同年次大会, ワークショップオーガナイザー.
2017.10.02～2017.10.03, 国立遺伝学研究所・研究集会「染色体構築と安定化を担う分子機構」, ミーティングオーガナイザー.
Friedrich Miescher Institute, Switzerland, 2019.12～2019.12.
Cold Spring Harbor Laboratory, UnitedStatesofAmerica, 2019.09～2019.09.
Karolinska institute, Sweden, 2018.05～2018.05.
Cold Spring Harbor Laboratory, UnitedStatesofAmerica, 2017.09～2017.09.
Stanford University, UnitedStatesofAmerica, 2017.05～2017.05.
2018年度～2019年度, 新学術領域研究, 代表, 相同性依存的修復の品質管理機構を次世代シーケンス技術を用いて探る.
2016年度～2018年度, 挑戦的萌芽研究, 代表, ミスマッチ修復による合成エラー修復と誤った相同組み換え抑制の統一的理解.
2013年度～2016年度, 若手研究(A,B), 代表, コヒーシンが染色体接着と二重鎖切断修復に機能する機構の試験管内再構成による解析.
2017年度～2019年度, 基盤研究(B), 代表, ミスマッチ修復システムによる相同組換え品質保証機構の動作原理の解明.
QIR 九州大学学術情報リポジトリ システム情報科学研究院
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