Heterochromatic gene silencing is an important form of gene regulation that usually requires specific histone modifications. A popular model posits that inheritance of modified histones, especially in the form of H3-H4 tetramers, underlies inheritance of heterochromatin. Because H3-H4 tetramers are randomly distributed between daughter chromatids during DNA replication, rare occurrences of asymmetric tetramer inheritance within a heterochromatic domain would have the potential to destabilize heterochromatin. This model makes a prediction that shorter heterochromatic domains would experience unbalanced tetramer inheritance more frequently, and thereby be less stable. In contrast to this prediction, we found that shortening a heterochromatic domain in Saccharomyces had no impact on the strength of silencing nor its heritability. Additionally, we found that replisome mutations that disrupt inheritance of H3-H4 tetramers had only minor effects on heterochromatin stability. These findings suggest that histones carry little or no memory of the heterochromatin state through DNA replication.
Sequencing data have been deposited in GEO under accession code GSE136897.
Nucleosome profiles in strains with different numbers of nucleosomes at HML and HMRNCBI Gene Expression Omnibus, GSE136897.
- Jasper Rine
- Jasper Rine
- Daniel S Saxton
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
- Tim Formosa, University of Utah School of Medicine, United States
© 2019, Saxton & Rine
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