近日，美国宾夕法尼亚大学的Jennifer E. Phillips-Cremins研究组取得进展，建立了一个名为LADL的技术，其通过光线激活染色质的动态环化参与调控内源性基因的表达。2019年7月出版的国际知名学术期刊《自然—方法学》发表了这一成果。

研究人员设计了一类新的合成构架蛋白，可用于蓝光控制的3D基因组重排。研究团队使用CRISPR gRNA将LADL系统定位于两个基因组位点，通过光诱导隐花色素2与dCas9-CIBN融合蛋白的异源二聚化，使两个位点发生空间共定位。研究人员使用LADL将一个延伸增强子（SE）从其内源性Klf4靶基因重定向到Zfp462基因的启动子。利用单分子RNA-FISH技术，研究人员证实了Zfp462与SE环化的重新形成与Zfp462的表达适度增加相关。因此，LADL技术可以在在没有外源性化学辅助因子的情况下促进基因组位点的共定位，并为未来实现人工操控短时间内可逆的周期性环化提供可能。

研究人员表示，哺乳动物的基因组被折叠成了成千上万的长距离环化结构。环化与基因组功能之间的因果关系还了解甚少，此外短时间内动态环化的程度也是未知的。

附：英文原文

Title: LADL: light-activated dynamic looping for endogenous gene expression control

Author: Ji Hun Kim, Mayuri Rege, Jacqueline Valeri, Margaret C. Dunagin, Aryeh Metzger, Katelyn R. Titus, Thomas G. Gilgenast, Wanfeng Gong, Jonathan A. Beagan, Arjun Raj, Jennifer E. Phillips-Cremins

Issue&Volume: Volume 16 Issue 7, July 2019

Abstract: Mammalian genomes are folded into tens of thousands of long-range looping interactions. The cause-and-effect relationship between looping and genome function is poorly understood, and the extent to which loops are dynamic on short time scales remains an unanswered question. Here, we engineer a new class of synthetic architectural proteins for directed rearrangement of the three-dimensional genome using blue light. We target our light-activated-dynamic-looping (LADL) system to two genomic anchors with CRISPR guide RNAs and induce their spatial colocalization via light-induced heterodimerization of cryptochrome 2 and a dCas9-CIBN fusion protein. We apply LADL to redirect a stretch enhancer (SE) away from its endogenous Klf4 target gene and to the Zfp462 promoter. Using single-molecule RNAFISH, we demonstrate that de novo formation of the Zfp462-SE loop correlates with a modest increase in Zfp462 expression. LADL facilitates colocalization of genomic loci without exogenous chemical cofactors and will enable future efforts to engineer reversible and oscillatory loops on short time scales.

DOI: 10.1038/s41592-019-0436-5

Source:https://www.nature.com/articles/s41592-019-0436-5