Expression Noise Can Generate Heterogeneity in Viability but Does Not Affect Cell-to-Cell Epigenetic Silencing of Subtelomeric in Yeast.

Chromatin structure clearly modulates gene expression noise, but the reverse influence has never been investigated, namely how the cell-to-cell expression heterogeneity of chromatin modifiers may generate variable rates of epigenetic modification. Sir2 is a well-characterized histone deacetylase of the Sirtuin family. It strongly influences chromatin silencing, especially at telomeres, subtelomeres and rDNA. This ability to influence epigenetic landscapes makes it a good model to study the largely unexplored interplay between gene expression noise and other epigenetic processes leading to phenotypic diversification. Here, we addressed this question by investigating whether noise in the expression of was associated with cell-to-cell heterogeneity in the frequency of epigenetic silencing at subtelomeres in Using cell sorting to isolate subpopulations with various expression levels, we found that heterogeneity in the cellular concentration of Sir2 does not lead to heterogeneity in the epigenetic silencing of subtelomeric between these subpopulations. We also noticed that expression noise can generate cell-to-cell variability in viability, with lower levels being associated with better viability. This work shows that expression fluctuations are not sufficient to generate cell-to-cell heterogeneity in the epigenetic silencing of at subtelomeres in but can strongly affect cellular viability.