Related Experiment Video
Updated: Mar 13, 2026
Reusable Single Cell for Iterative Epigenomic Analyses
Published on: February 11, 2022
Live-cell single-molecule tracking reveals co-recognition of H3K27me3 and DNA targets polycomb Cbx7-PRC1 to chromatin
Chao Yu Zhen1, Roubina Tatavosian1, Thao Ngoc Huynh1
1Department of Chemistry, University of Colorado Denver, Denver, United States.
Abstract:
The Polycomb PRC1 plays essential roles in development and disease pathogenesis. Targeting of PRC1 to chromatin is thought to be mediated by the Cbx family proteins (Cbx2/4/6/7/8) binding to histone H3 with a K27me3 modification (H3K27me3). Despite this prevailing view, the molecular mechanisms of targeting remain poorly understood. Here, by combining live-cell single-molecule tracking (SMT) and genetic engineering, we reveal that H3K27me3 contributes significantly to the targeting of Cbx7 and Cbx8 to chromatin, but less to Cbx2, Cbx4, and Cbx6. Genetic disruption of the complex formation of PRC1 facilitates the targeting of Cbx7 to chromatin. Biochemical analyses uncover that the CD and AT-hook-like (ATL) motif of Cbx7 constitute a functional DNA-binding unit. Live-cell SMT of Cbx7 mutants demonstrates that Cbx7 is targeted to chromatin by co-recognizing of H3K27me3 and DNA. Our data suggest a novel hierarchical cooperation mechanism by which histone modifications and DNA coordinate to target chromatin regulatory complexes.
Insights
Polycomb Repressor Complex 1 (PRC1) targets chromatin via histone modifications and DNA. This study reveals how Cbx7 and Cbx8 recognize H3K27me3 and DNA for precise chromatin targeting.
Area of Science:
- Molecular Biology
- Epigenetics
- Chromatin Biology
Background:
- Polycomb PRC1 is crucial for development and disease.
- PRC1 targeting is linked to Cbx proteins binding H3K27me3.
- Mechanisms of PRC1 chromatin targeting are not fully understood.
Purpose of the Study:
- To elucidate the molecular mechanisms of PRC1 targeting to chromatin.
- To investigate the roles of histone modifications and DNA in Cbx protein targeting.
- To understand the targeting specificity of different Cbx family members.
Main Methods:
- Live-cell single-molecule tracking (SMT).
- Genetic engineering and disruption of PRC1 complex formation.
- Biochemical analyses of Cbx protein domains.
- SMT of Cbx7 mutants.
Main Results:
- H3K27me3 significantly contributes to Cbx7 and Cbx8 targeting, less to Cbx2, Cbx4, Cbx6.
- Disrupting PRC1 complex formation enhances Cbx7 chromatin targeting.
- Cbx7's CD and AT-hook-like (ATL) motifs form a DNA-binding unit.
- Cbx7 targets chromatin by co-recognizing H3K27me3 and DNA.
Conclusions:
- A novel hierarchical mechanism coordinates histone modifications and DNA for chromatin targeting.
- Cbx7 utilizes a dual recognition mechanism involving H3K27me3 and DNA.
- PRC1 targeting specificity is influenced by individual Cbx protein properties and PRC1 complex integrity.
Related Concept Videos
01:32Chromatin Modification in iPS Cells
Compact chromatin makes reprogramming difficult. Enzymes, such as histone demethylases and acetyltransferases, are often added during reprogramming to loosen the chromatin, making the DNA more accessible to transcription factors. Molecules that inhibit histone...
02:36Chromatin Immunoprecipitation- ChIP
Types of ChIP
ChIP can be divided into two types - X-ChIP and N-ChIP. X-ChIP involves in vivo cross-linking of histones and regulatory proteins to DNA, fragmenting the DNA by sonication, and isolating the protein-DNA...
02:38Heterochromatin
Constitutive heterochromatin: It is a highly compact region of chromatin that is mostly concentrated in the centromere and telomere. Unlike euchromatin, the amino acid at...