Nucleosome Turnover Regulates Histone Methylation Patterns over the Genome

Area of Science:

• Epigenetics
• Molecular Biology
• Genomics

Background:

• Nucleosome turnover is a rapid process occurring multiple times per cell cycle.
• Histone modifications play crucial roles in regulating gene expression and maintaining genome stability.
• H3K79 methylation is a key epigenetic mark regulated by the methyltransferase Dot1l, with no known demethylase.

Purpose of the Study:

• To investigate the impact of nucleosome turnover on the epigenetic landscape, specifically H3K79 methylation.
• To determine how nucleosome turnover rates influence the valency (mono-, di-, tri-) of H3K79 methylation.
• To explore whether nucleosome turnover models can predict the genomic propagation and distribution of epigenetic marks.

Main Methods:

• Utilized chemical-induced proximity (CIP) to investigate H3K79 methylation dynamics.
• Performed nucleosome turnover simulations across the genome.
• Conducted a meta-analysis of other conserved histone modifications in worms, flies, and mice.

Main Results:

• Nucleosome turnover rates were found to determine the valency of H3K79 methylation.
• Nucleosome turnover simulations accurately predicted the genomic propagation and asymmetric distribution of H3K79 methylation toward transcriptional units.
• Nucleosome turnover models successfully predicted both the valency and chromosomal propagation of other conserved histone methylation marks.

Conclusions:

• Nucleosome turnover is a critical determinant of H3K79 methylation valency.
• Nucleosome turnover dynamics govern the genome-wide propagation and distribution patterns of epigenetic marks.
• The turnover of modified nucleosomes represents a general mechanism for epigenetic mark propagation and influences methylation valence across diverse organisms.