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Biophysical characterization of histone H3.3 K27M point mutation
Szabolcs Hetey1, Beáta Boros-Oláh1, Tímea Kuik-Rózsa1
1MTA-DE Momentum, Genome Architecture and Recombination Research Group, Research Centre for Molecular Medicine, Department of Biochemistry and Molecular Biology, University of Debrecen, Debrecen 4032, Hungary.
Abstract:
Lysine 27 to methionine (K27 M) mutation of the histone variant H3.3 drives the formation of an aggressive glioblastoma multiforme tumor in infants. Here we analyzed how the methionine substitution alters the stability of H3.3 nucleosomes in vitro and modifies its kinetic properties in live cells. We also determined whether the presence of mutant nucleosomes perturbed the mobility of the PRC2 subunit Ezh2 (enhancer-of-zeste homolog 2). We found that K27 M nucleosomes maintained the wild-type molecular architecture both at the level of bulk histones and single nucleosomes and followed similar diffusion kinetics to wild-type histones in live cells. Nevertheless, we observed a remarkable differential recovery of Ezh2 in response to transcriptional stress that was accompanied by a faster diffusion rate of the mobile fraction of Ezh2 and a significantly increased immobile fraction, suggesting tighter chromatin binding of Ezh2 upon transcription inhibition. The differential recovery of Ezh2 was dependent on transcription, however, it was independent from K27 M mutation status. These biophysical characteristics shed more light on the mechanism of histone H3.3 K27M in glioma genesis in relation to the kinetic properties of Ezh2.
Insights
The K27M mutation in histone H3.3 does not alter nucleosome stability but affects EZH2 protein binding to chromatin during transcriptional stress in infant glioblastoma.
Area of Science:
- Molecular Biology
- Epigenetics
- Cancer Research
Background:
- The histone H3.3 K27M mutation is a key driver of aggressive pediatric glioblastoma.
- Understanding the molecular mechanisms underlying H3.3 K27M-driven gliomagenesis is crucial for therapeutic development.
Purpose of the Study:
- To investigate the impact of the H3.3 K27M mutation on nucleosome stability and dynamics.
- To determine how the K27M mutation affects the mobility and chromatin binding of the PRC2 subunit EZH2.
- To elucidate the role of EZH2 kinetics in H3.3 K27M-mediated glioma formation.
Main Methods:
- In vitro analysis of H3.3 K27M nucleosome stability and molecular architecture.
- Live-cell imaging to study histone diffusion kinetics and EZH2 mobility.
- Assessment of EZH2 recovery kinetics under transcriptional stress.
Main Results:
- H3.3 K27M nucleosomes exhibit wild-type molecular architecture and diffusion kinetics.
- Transcriptional stress induces differential EZH2 recovery, with faster diffusion and increased chromatin binding of the mobile fraction.
- EZH2 differential recovery is dependent on transcription but independent of the K27M mutation status.
Conclusions:
- The H3.3 K27M mutation does not directly alter nucleosome stability or basic histone dynamics.
- Transcriptional stress significantly impacts EZH2 chromatin binding dynamics, independent of the K27M mutation.
- These findings provide insights into the biophysical mechanisms of H3.3 K27M gliomagenesis related to EZH2 kinetic properties.
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