Distribution and Maintenance of Histone H3 Lysine 36 Trimethylation in Transcribed Locus

Post-translational modifications of core histones play an important role in the epigenetic regulation of chromatin dynamics and gene expression. In Saccharomyces cerevisiae methylation marks at K4, K36, and K79 of histone H3 are associated with gene transcription. Although Set2-mediated H3K36 methylation is enriched throughout the coding region of active genes and prevents aberrant transcriptional initiation within coding sequences, it is not known if transcription of one locus impacts the methylation pattern of neighbouring areas and for how long H3K36 methylation is maintained after transcription termination. Our results demonstrate that H3K36 methylation is restricted to the transcribed sequence only and the modification does not spread to adjacent loci downstream from transcription termination site. We also show that H3K36 trimethylation mark persists in the locus for at least 60 minutes after transcription inhibition, suggesting a short epigenetic memory for recently occurred transcriptional activity. Our results indicate that both replication-dependent exchange of nucleosomes and the activity of histone demethylases Rph1, Jhd1 and Gis1 contribute to the turnover of H3K36 methylation upon shut-down of transcription.