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基因座折叠机制决定了抗原受体基因组装的模式。

Locus folding mechanisms determine modes of antigen receptor gene assembly.

机构信息

Immunology Graduate Group, Perelman School of Medicine, University of Pennsylvania , Philadelphia, PA, USA.

Department of Pathology and Laboratory Medicine, Children's Hospital of Philadelphia, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA.

出版信息

J Exp Med. 2024 Feb 5;221(2). doi: 10.1084/jem.20230985. Epub 2024 Jan 8.

Abstract

The dynamic folding of genomes regulates numerous biological processes, including antigen receptor (AgR) gene assembly. We show that, unlike other AgR loci, homotypic chromatin interactions and bidirectional chromosome looping both contribute to structuring Tcrb for efficient long-range V(D)J recombination. Inactivation of the CTCF binding element (CBE) or promoter at the most 5'Vβ segment (Trbv1) impaired loop extrusion originating locally and extending to DβJβ CBEs at the opposite end of Tcrb. Promoter or CBE mutation nearly eliminated Trbv1 contacts and decreased RAG endonuclease-mediated Trbv1 recombination. Importantly, Trbv1 rearrangement can proceed independent of substrate orientation, ruling out scanning by DβJβ-bound RAG as the sole mechanism of Vβ recombination, distinguishing it from Igh. Our data indicate that CBE-dependent generation of loops cooperates with promoter-mediated activation of chromatin to juxtapose Vβ and DβJβ segments for recombination through diffusion-based synapsis. Thus, the mechanisms that fold a genomic region can influence molecular processes occurring in that space, which may include recombination, repair, and transcriptional programming.

摘要

基因组的动态折叠调节着许多生物学过程,包括抗原受体(AgR)基因的组装。我们发现,与其他 AgR 基因座不同,同型染色质相互作用和双向染色体环化都有助于构建 Tcrb,以实现有效的长距离 V(D)J 重组。在最 5'Vβ 片段(Trbv1)处失活 CTCF 结合元件(CBE)或启动子,会损害局部起始并延伸至 Tcrb 另一端的 DβJβ CBE 的环挤出。启动子或 CBE 突变几乎消除了 Trbv1 接触,并减少了 RAG 内切酶介导的 Trbv1 重组。重要的是,Trbv1 重排可以独立于底物取向进行,排除了 DβJβ 结合的 RAG 通过扫描作为 Vβ 重组的唯一机制,这将其与 Igh 区分开来。我们的数据表明,依赖 CBE 的环的产生与启动子介导的染色质激活合作,通过基于扩散的联会将 Vβ 和 DβJβ 片段并列,以进行重组。因此,折叠基因组区域的机制可以影响该空间中发生的分子过程,包括重组、修复和转录编程。

https://cdn.ncbi.nlm.nih.gov/pmc/blobs/dc04/10772921/f35726f423b3/JEM_20230985_Fig1.jpg

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