小柯机器人

研究揭示小鼠祖B细胞抗体重链基因位点收缩和V(D)J重组的调控机制
2021-01-15 15:39

哈佛大学医学院/波士顿儿童医院的 Frederick W. Alt、戴海强等人发现,染色质环挤出介导生理Igh基因座收缩以实现RAG重排。2021年1月13日,国际学术期刊《自然》在线发表了这一成果。

研究人员发现小鼠原代祖细胞中在基因座收缩仍然发生的情况下,2.4 Mb VH完整基因座的倒置消除了VH- JH重组信号序列(RSSs)和cryptic RSS重排。此外,这种翻转作用激活了沿相反方向cryptic VH-RSS的利用,也激活了RAG扫描,通过几个聚合CTCF结合元件(CBE)结构域到达端粒VH基因座之外。

总而言之,这些发现暗示了祖B细胞中CBE障碍的广泛失控促进了染色质环挤出介导的VH基因座RAG扫描。研究进一步发现,与缺乏收缩和RAG扫描的v-Abl转化祖B细胞系相比,cohesin释放因子WAPL在小鼠原代祖B细胞中表达非常低。相应地,在v-Abl转化细胞系中WAPL缺失激活了这两个过程,进一步证明了染色质环挤出在基因座收缩中的功能。

研究人员表示,RAG核酸内切酶通过结合重组中心(RC)内的JH-RSS,并线性扫描上游染色质(由cohesin介导的染色质环挤出)以聚合D-RSS,从而在前体B细胞中驱动Igh V(D)J重组。融合定向RSS和cryptic RSS是远程RAG扫描的固有属性。从DJH-RC-RSS到上游收敛VH-RSS的RAG扫描受近端D-CBE的阻碍。前体B细胞经历了VH基因座的不稳定收缩,该收缩为远端VHs进入DJH-RC提供了便利。

附:英文原文

Title: Loop extrusion mediates physiological Igh locus contraction for RAG scanning

Author: Hai-Qiang Dai, Hongli Hu, Jiangman Lou, Adam Yongxin Ye, Zhaoqing Ba, Xuefei Zhang, Yiwen Zhang, Lijuan Zhao, Hye Suk Yoon, Aimee M. Chapdelaine-Williams, Nia Kyritsis, Huan Chen, Kerstin Johnson, Sherry Lin, Andrea Conte, Rafael Casellas, Cheng-Sheng Lee, Frederick W. Alt

Issue&Volume: 2021-01-13

Abstract: RAG endonuclease initiates Igh V(D)J recombination in progenitor B cells by binding a JH-recombination signal sequence (RSS) within a recombination centre (RC) and then linearly scanning upstream chromatin, presented by loop extrusion mediated by cohesin, for convergent D-RSSs1,2. The utilization of convergently oriented RSSs and cryptic RSSs is intrinsic to long-range RAG scanning3. Scanning of RAG from the DJH-RC-RSS to upstream convergent VH-RSSs is impeded by D-proximal CTCF-binding elements (CBEs)2,3,4,5. Primary progenitor B cells undergo a mechanistically undefined contraction of the VH locus that is proposed to provide distal VHs access to the DJH-RC6,7,8,9. Here we report that an inversion of the entire 2.4-Mb VH locus in mouse primary progenitor B cells abrogates rearrangement of both VH-RSSs and normally convergent cryptic RSSs, even though locus contraction still occurs. In addition, this inversion activated both the utilization of cryptic VH-RSSs that are normally in opposite orientation and RAG scanning beyond the VH locus through several convergent CBE domains to the telomere. Together, these findings imply that broad deregulation of CBE impediments in primary progenitor B cells promotes RAG scanning of the VH locus mediated by loop extrusion. We further found that the expression of wings apart-like protein homologue (WAPL)10, a cohesin-unloading factor, was low in primary progenitor B cells compared with v-Abl-transformed progenitor B cell lines that lacked contraction and RAG scanning of the VH locus. Correspondingly, depletion of WAPL in v-Abl-transformed lines activated both processes, further implicating loop extrusion in the locus contraction mechanism.

DOI: 10.1038/s41586-020-03121-7

Source: https://www.nature.com/articles/s41586-020-03121-7

Nature:《自然》,创刊于1869年。隶属于施普林格·自然出版集团,最新IF:69.504
官方网址:http://www.nature.com/
投稿链接:http://www.nature.com/authors/submit_manuscript.html


本期文章:《自然》:Online/在线发表

分享到:

0