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2013 年度 実施状況報告書

AIDによるゲノム再構成に伴うクロマチン制御

研究課題

研究課題/領域番号 24590352
研究機関京都大学

研究代表者

BEGUM NasimAra  京都大学, 医学(系)研究科(研究院), 准教授 (80362507)

キーワードAID / TOP1 / CSR / SHM / H3K4me3 / FACT / SPT6 / Genomic instability
研究概要

AID induces genomic instability at IgH locus during antibody gene diversification. It also induces aberrant genomic rearrangement responsible for oncogenic chromosomal translocations. Therefore, it is important to understand the underlying mechanism of AID induced genomic break and repair.
Study of histone chaperones, FACT and SPT6, revealed the importance of chromatin regulation in AID induced DNA break. Unlike FACT, SPT6 regulated the chromatin of both AID locus and the AID-target loci. Interestingly, H3K36me3 and H3K4me3 chromatin marks controlled the two regulations by SPT6, respectively. Highly mutated target regions also showed a strong correlation with FACT, histone variant H3.3 and H3K4me3 enrichment. We could publish these observations, and also successfully characterized the H3K4me3 enriched Top1-DNA cleavage complex isolated from AID activated cells.
Chromatin proteins and histone epigenetic marks are also important at the repair step of the recombination. We have isolated a novel adapter protein that supports CSR specific repair complex formation on the chromatin through acetylated histone bridging. The complex regulated the recruitment of UNG, a base excision repair enzyme whose deficiency leads to severe CSR block. UNG appears to regulate the recruitment of several key repair factors involved in CSR synapse formation and the DNA break end joining. We have recently published this novel phenomenon of UNG.

現在までの達成度 (区分)
現在までの達成度 (区分)

2: おおむね順調に進展している

理由

Among the identified CSR associated novel chromatin regulators, two of them appeared to be working at the repair-recombination phase of CSR. Interestingly, we found that this repair complex contained UNG, a repair enzyme whose deficiency severely blocked CSR. As we have been exploring a non-canonical mode of action of UNG, this unexpected coincidence helped to understand the functional relevance and the mechanism of action of UNG and the novel chromatin protein identified.
We also made considerable progress on understanding AID induced DNA-cleavage complex formation. While FACT is required to generate H3K4me3 dependent DNA cleavage complex formation with Top1, another associated chromatin remodeling protein plays an important role in Top1 loading in the transcribed S-region. This dual mode of Top1 regulation in AID activated B cells is a very promising finding, especially in the context of DNA break events associated with CSR, SHM, and aberrant chromosomal rearrangements.

今後の研究の推進方策

(1) Chromatin factors and features involved in AID induced DNA damage: We will complete the characterization of the H3K4me3-Top1-DNA cleavage complex in respect of function. Although MS analysis identified several chromatin factors, which are likely involved in AID induced DNA break and recombination processes, we plan to do all types of functional analyses for the two chromatin factors which may explain the functional significance of the H3K4me3 complex.
(2) Chromatin factors and features involved in AID induced recombination: We will mainly focus on the identified bromodomain chromatin adapter protein. To complete the work we need to do (i) extensive ChIP analysis of various CSR repair factors after knocking down the adapter protein or by inhibiting its interaction with the acetylated histones, and (ii) demonstration of the general DNA repair efficiency of the adapter protein such as radiation induced global DNA damage or meganuclease induced site-specific DNA cleavage.
(3) Development of DNA cleavage regulation assay and generation SPT6-CKO mice: We have generated S-region specific TALE binder proteins to examine their ability to interfere with the S-region repeat structure and DNA cleavage. As ChIP assay for the TALE-binders turned out to be very inefficient, we could not validate their binding specificity. Now, we are planning to examine the CSR regulation property by an alternative functional assay. We are still in the process of B cell specific SPT6-CKO mice generation for in vivo chromatin regulation study.

  • 研究成果

    (9件)

すべて 2014 2013

すべて 雑誌論文 (3件) (うち査読あり 3件) 学会発表 (5件) (うち招待講演 1件) 図書 (1件)

  • [雑誌論文] Differential regulation of S-region hypermutation and class-switch recombination by noncanonical functions of uracil DNA glycosylase2014

    • 著者名/発表者名
      Yousif AS, Stanlie A, Mondal S, Honjo T, Begum NA.
    • 雑誌名

      Proc Natl Acad Sci USA

      巻: 111 ページ: E1016-24

    • DOI

      doi: 10.1073/pnas.1402391111

    • 査読あり
  • [雑誌論文] C-terminal region of activation-induced cytidine deaminase (AID) is required for efficient class switch recombination and gene conversion2014

    • 著者名/発表者名
      Sabouri S, Kobayashi M, Begum NA, Xu J, Hirota K, Honjo T.
    • 雑誌名

      Proc Natl Acad Sci USA

      巻: 111 ページ: 2253-8

    • DOI

      doi: 10.1073/pnas.1324057111

    • 査読あり
  • [雑誌論文] Accumulation of the FACT complex, as well as histone H3.3, serves as a target marker for somatic hypermutation2013

    • 著者名/発表者名
      Aida M, Hamad N, Stanlie A, Begum NA, Honjo T.
    • 雑誌名

      Proc Natl Acad Sci USA

      巻: 110 ページ: 7784-9

    • DOI

      doi: 10.1073/pnas.1305859110

    • 査読あり
  • [学会発表] Chromatin adapter Brd4 serves as a repair platform for immunoglobulin class switch recombination2013

    • 著者名/発表者名
      Nasim A. Begum, Andre Stanlie, Masatoshi Aida and Tasuku Honjo
    • 学会等名
      42nd JSI Annual Meeting. Chiba, Japan
    • 発表場所
      Immunoglobulin gene diversification
    • 年月日
      20131211-20131213
  • [学会発表] The Non-Canonical function of UNG plays distinct roles in SHM and CSR2013

    • 著者名/発表者名
      Ashraf S. Yousif, Nasim A. Begum and Tasuku. Honjo
    • 学会等名
      42nd JSI Annual Meeting. Chiba, Japan
    • 発表場所
      Immunoglobulin gene diversification
    • 年月日
      20131211-20131213
  • [学会発表] Antibody gene diversification by AID requires specialized chromatin regulators2013

    • 著者名/発表者名
      Nasim A. Begum, Andre Stanlie, Masatoshi Aida and Tasuku Honjo
    • 学会等名
      World Congress on Advances in Oncology & International Symposium on Molecular Medicine. Crete, Greece.
    • 発表場所
      Immunology & Molecular Oncology
    • 年月日
      20131010-20131012
    • 招待講演
  • [学会発表] The Non-Canonical function of UNG in AID induced Antibody Gene Diversification2013

    • 著者名/発表者名
      Ashraf S. Yousif, Nasim A. Begum and Tasuku Honjo
    • 学会等名
      15th ICI (International Congress of Immunology). Milan, Italy
    • 発表場所
      Session B cell development and plasma cell differentiation
    • 年月日
      20130822-20130827
  • [学会発表] Dynamic Interplay of Transcription Elongation Factors and Histone Modifications in regulating B cells Class Switch Recombination2013

    • 著者名/発表者名
      Andre Stanlie, Nasim A. Begum and Tasuku Honjo
    • 学会等名
      SIgN-IFREC Immunology Winter School. Singapore
    • 発表場所
      Immunology
    • 年月日
      20130120-20130125
  • [図書] Mol2014

    • 著者名/発表者名
      Begum Nasim Ara
    • 総ページ数
      12-13
    • 出版者
      Nol.

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公開日: 2015-05-28  

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