# Ectopic Recruitment of the CTCF N-Terminal Domain with Two Proximal Zinc-Finger Domains as a Tool for 3D Genome Engineering

## TL;DR

Researchers created a tool using parts of the CTCF protein to engineer 3D genome structures without affecting gene activity.

## Contribution

A chimeric CTCF-based protein was developed for 3D genome engineering without altering gene expression.

## Key findings

- The chimeric CTCF protein formed new chromatin contacts at the HOXD locus.
- It restored chromatin loops lost after deletion of a CTCF-binding site.
- The protein did not bind CTCF motifs or affect epigenetic or transcription profiles.

## Abstract

Enhancer-promoter interactions occur in the chromatin loci delineated by the CCCTC-binding zinc-finger protein CTCF. CTCF binding is frequently perturbed in genetic disorders and cancer, allowing for misregulation of genes. Here, we developed a panel of chimeric proteins consisting of either full-length or truncated CTCF fused with programmable DNA-binding module dCas9 and fluorescent tracker EGFP. We found that the recruitment of a chimeric protein based on the CTCF N-terminal domain and two zinc-finger domains to the human HOXD locus leads to the de novo formation of a spatial contact with a nearby cohesin/CTCF-bound region, anchoring several chromatin loops. This chimeric protein did not show binding to CTCF motifs and did not affect the epigenetic and transcription profile of the locus. Recruitment of this chimeric protein is also able to restore chromatin loops, lost after deletion of an endogenous CTCF-binding site. Together, our data indicate that the ectopic recruitment of the CTCF N-terminal part could be an appropriate tool for 3D genome engineering.