Catching histones by the tail: A new probe to track histone modifications in living cells

September 12, 2016, Tokyo Institute of Technology
Single chain variable fragment of antibody (scFv) tagged with green fluorescent protein (GFP) recognizes and binds to histone H4 post-translationally modified by the addition of a single methyl group (monomethylation) at lysine 20 (H4K20me1). Credit: © 2016 The Author(s). Published by Elsevier Ltd.

Scientists at Tokyo Institute of Technology have developed a sensitive fluorescent antibody probe that specifically detects monomethylation of lysine 20 in histone H4 in living cells. This research has future implications and can be used to monitor the dynamics of histone modifications and genome integrity in single living cells without disturbing cellular functions.

Genomic integrity in is maintained by packaging of nuclear DNA into chromatin, which protects it from damage and controls gene replication and expression. Histones are the primary protein components of chromatin and their post-translational modifications regulate chromatin structure and play a fundamental role in biological processes such as DNA repair, DNA replication, mitosis, etc. Among the modifications, methylation of histone H4 at lysine 20 (H4K20) is evolutionarily conserved from yeast to humans and exists in three states, mono-, di- and trimethylation, each of which have distinct biological roles. Conventional techniques studying regulation by histone modifications are limited to fixed (dead) cells, thus preventing assessment of histone modification in single, living cells.

To address this challenge, a group of scientists led by Prof. Kimura from the Institute of Innovative Research, Tokyo Institute of Technology, generated a genetically encoded live-cell imaging probe for sensitive monitoring of the intracellular spatiotemporal dynamics of H4K20 monomethylation (H4K20me1). The probe, called mintbody (modification-specific intracellular antibody), is a single-chain variable fragment tagged with a fluorescent protein that demonstrates high specificity for H4K20me1 over di- and trimethylation in living yeast, mammalian cells, and even multicellular organisms.

H4K20me1 is most likely associated with the tight packing of a redundant (inactivated) female X chromosome (Xi) into heterochromatin. In a roundworm Caenorhabditis elegans model, Prof. Kimura and colleagues showed that the H4K20me1-mintbody could be used to monitor changes in H4K20me1 over the cell cycle and localization of dosage-compensated X chromosomes without disrupting cell function. Thus, the new mintbody can overcome the challenges associated with visualizing and tracking histone modifications directly in living cells.

This research also identified key amino acids responsible for H4K20me1-mintbody conformational stability, solubility, and consequently, functional performance using X-ray crystallography and genetic analyses. Thus, a possible solution to the existing problem of limited solubility of intracellularly expressed antibody fragments due to aberrant folding in the cytoplasm that restricted their use was formulated.

In the future, development of additional mintbodies specific to diverse post-translational will facilitate the identification of regulatory mechanisms that control epigenetic modifications.

Explore further: The discovery of a totally new kind of 'mark' in human cell nucleus

More information: Yuko Sato et al, A Genetically Encoded Probe for Live-Cell Imaging of H4K20 Monomethylation, Journal of Molecular Biology (2016). DOI: 10.1016/j.jmb.2016.08.010

Related Stories

Packaging and unpacking of the genome

November 6, 2015

DNA represents a dynamic form of information, balancing efficient storage and access requirements. Packaging approximately 1.8m of DNA into something as small as a cell nucleus is no mean feat, but unpacking it again to access ...

Recommended for you

Inert nitrogen forced to react with itself

March 21, 2019

Constituting over 78 % of the air we breathe, nitrogen is the element found the most often in its pure form on earth. The reason for the abundance of elemental nitrogen is the incredible stability and inertness of dinitrogen ...

Two-step path to shrinking worker bee gonads

March 21, 2019

The dramatic difference in gonad size between honey bee queens and their female workers in response to their distinct diets requires the switching on of a specific genetic program, according to a new study publishing March ...

Plant immunity cut to size

March 21, 2019

An international team based in Ghent, Belgium (VIB-UGent Center for Plant Systems Biology) and Basel, Switzerland (University of Basel), found a link between a class of enzymes and immune signals that is rapidly triggered ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.