染色体ループドメインは,抗原受容体遺伝子の再結合を制御する
Jiazhi Hu1, Yu Zhang1, Lijuan Zhao1
1Howard Hughes Medical Institute; Program in Cellular and Molecular Medicine, Boston Children's Hospital, Boston, MA 02115, USA; Department of Genetics, Harvard Medical School, Boston, MA 02115, USA.
Cell
|November 24, 2015
まとめ
RAG酵素はV(D) J再結合のためのDNA断裂を開始します. 新しい研究は,RAGによる多数の"非標的"断絶を特定し,リンパ球におけるDNA修復とクロマチン組織のメカニズムを明らかにしています.
科学分野:
- 分子生物学
- 免疫学
- 遺伝学
背景:
- RAG酵素は,発達中のリンパ球におけるV(D) J再結合の開始に不可欠です.
- V(D) J再結合は,特定の再結合信号配列 (RSS) で正確なDNA断絶を必要とします.
研究 の 目的:
- RAGによって生成された"非標的"DNAの断裂を特定し,特徴づけること.
- 染色体領域内のRAG活性を調節するメカニズムを理解する.
主な方法:
- エンドゲンと子宮外RSSのペアで生成されたRAGのブレイクを利用した.
- 対象外ブレイク位置とCTCF結合要素 (CBE) とループドメインとの関連を分析した.
- RAGの標的外活動における方向性依存と線形追跡の役割を調査した.
- CBEベースのIgHロカス要素の削除がRAG活動分布に与える影響を検証した.
主要な成果:
- CACモチーフで発生する多数のRAGオフターゲットブレイクを特定しました.
- オフターゲットのブレイクは,主にコンバージントCTCF-バインディングエレメント (CBE) 付近のループドメインに限られていた.
- 大きなループドメイン内のRAGのオフターゲットの指向依存性が実証され,線形追跡が示唆されています.
- 染色体トランスロケーションにおける主要なRAGオフターゲットは,ループ内のエンハンサーで収束RSSペアを含むことが判明した.
- IgHロカスCBE要素の削除により,V(D) J再結合領域とRAGのオン/オフターゲットの分布が変化した.
結論:
- RAGの活動は発達的に集中し,クロマチンのループ内の特定のDNAモチーフでオフターゲットブレイクが発生します.
- CBEのような要素によって調節されるクロマチンのドメインは,V(D) J再結合などの生物学的プロセスを利用し,制御する役割を果たします.
- ループドメイン内の線形追跡を伴うメカニズムは,RAGのターゲット外の活動の空間的規制に貢献します.
関連する概念動画
Diversity of Antigen Receptors
2.1K
Antigen receptors are essential components of the immune system crucial in defending the body against foreign invaders. These receptors are present on the surface of B and T cells, enabling them to recognize antigens and mount an appropriate immune response.
Before encountering any antigen, lymphocytes express these receptors. On B cells, the antigen receptor is a membrane-bound antibody molecule called BCR; on T cells, it is a T cell receptor or TCR. B and T cell receptors are composed of two...
Before encountering any antigen, lymphocytes express these receptors. On B cells, the antigen receptor is a membrane-bound antibody molecule called BCR; on T cells, it is a T cell receptor or TCR. B and T cell receptors are composed of two...
2.1K
Conservative Site-specific Recombination and Phase Variation
7.3K
Because the DNA segments are cut and reorganized in a direction-specific manner, site-specific recombination has emerged as an efficient genetic engineering technique. Flippase and Cyclization recombinases or Flp and Cre, respectively, are two members of the tyrosine recombinase family derived from bacteriophages, that are used to mediate site-specific DNA insertions, deletions, and targeted expression of proteins in mammalian cell lines.
The recognition sites for Cre recombinase called LoxP...
The recognition sites for Cre recombinase called LoxP...
7.3K
Exon Recombination
4.3K
The evolution of new genes is critical for speciation. Exon recombination, also known as exon shuffling or domain shuffling, is an important means of new gene formation. It is observed across vertebrates, invertebrates, and in some plants such as potatoes and sunflowers. During exon recombination, exons from the same or different genes recombine and produce new exon-intron combinations, which might evolve into new genes.
Exon shuffling follows “splice frame rules.” Each exon...
Exon shuffling follows “splice frame rules.” Each exon...
4.3K
Crossing Over
7.2K
Crossing over is the exchange of genetic information between homologous chromosomes during prophase I of meiosis I. Genetic recombination gives rise to allelic diversity in the newly formed daughter cells. In humans, crossing over produces genetically distinct haploid egg and sperm cells that undergo fertilization to produce unique offspring. Before cell division starts, the germ cell’s chromosome(s) undergo duplication in the S phase of the cell cycle. As the cells enter prophase I,...
7.2K
Crossing Over
174.2K
Unlike mitosis, meiosis aims for genetic diversity in its creation of haploid gametes. Dividing germ cells first begin this process in prophase I, where each chromosome—replicated in S phase—is now composed of two sister chromatids (identical copies) joined centrally.
The homologous pairs of sister chromosomes—one from the maternal and one from the paternal genome—then begin to align alongside each other lengthwise, matching corresponding DNA positions in a process...
The homologous pairs of sister chromosomes—one from the maternal and one from the paternal genome—then begin to align alongside each other lengthwise, matching corresponding DNA positions in a process...
174.2K
Gene Conversion
10.9K
Other than maintaining genome stability via DNA repair, homologous recombination plays an important role in diversifying the genome. In fact, the recombination of sequences forms the molecular basis of genomic evolution. Random and non-random permutations of genomic sequences create a library of new amalgamated sequences. These newly formed genomes can determine the fitness and survival of cells. In bacteria, homologous and non-homologous types of recombination lead to the evolution of new...
10.9K


