1. Chromosomes and Gene Expression
  2. Genetics and Genomics

Distinguishing between recruitment and spread of silent chromatin structures in Saccharomyces cerevisiae

  1. Molly Brothers
  2. Jasper Rine  Is a corresponding author
  1. University of California, Berkeley, United States
https://doi.org/10.7554/eLife.75653
Share this article
Cite this article
  1. Molly Brothers
  2. Jasper Rine
(2022)
Distinguishing between recruitment and spread of silent chromatin structures in Saccharomyces cerevisiae
eLife 11:e75653.
https://doi.org/10.7554/eLife.75653
  2. Download BibTeX
  3. Download .RIS

Abstract

The formation of heterochromatin at HML, HMR, and telomeres in Saccharomyces cerevisiae involves two main steps: Recruitment of Sir proteins to silencers and their spread throughout the silenced domain. We developed a method to study these two processes at single base-pair resolution. Using a fusion protein between the heterochromatin protein Sir3 and the non-site-specific bacterial adenine methyltransferase M.EcoGII, we mapped sites of Sir3-chromatin interactions genome-wide using long-read Nanopore sequencing to detect adenines methylated by the fusion protein and by ChIP-seq to map the distribution of Sir3-M.EcoGII. A silencing-deficient mutant of Sir3 lacking its Bromo-Adjacent Homology (BAH) domain, sir3-bah∆, was still recruited to HML, HMR, and telomeres. However, in the absence of the BAH domain, it was unable to spread away from those recruitment sites. Overexpression of Sir3 did not lead to further spreading at HML, HMR, and most telomeres. A few exceptional telomeres, like 6R, exhibited a small amount of Sir3 spreading, suggesting that boundaries at telomeres responded variably to Sir3 overexpression. Finally, by using a temperature-sensitive allele of SIR3 fused to M.ECOGII, we tracked the positions first methylated after induction and found that repression of genes at HML and HMR began before Sir3 occupied the entire locus.

Data availability

All strains (Supplementary File 1) and plasmids (Supplementary File 2) are available upon request. Sequencing data is available in GEO under the SuperSeries GSE190137. ChIP-seq and DIP-seq data are under accession code GSE189038 in the SuperSeries. Nanopore data are under accession code GSE190136 in the SuperSeries.

The following data sets were generated
The following previously published data sets were used

Article and author information

Author details

  1. Molly Brothers

    Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, United States
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0002-6114-3393

  2. Jasper Rine

    Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, United States
    For correspondence
    jrine@berkeley.edu
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0003-2297-9814

Funding

National Science Foundation (1752814)

  • Molly Brothers

National Institutes of Health (R35 GM139488)

  • Jasper Rine

The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.

Copyright

© 2022, Brothers & Rine

This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.

Metrics

  • 1,781
    views
  • 232
    downloads
  • 19
    citations

Views, downloads and citations are aggregated across all versions of this paper published by eLife.

Download links

A two-part list of links to download the article, or parts of the article, in various formats.

Downloads (link to download the article as PDF)

Open citations (links to open the citations from this article in various online reference manager services)

Cite this article (links to download the citations from this article in formats compatible with various reference manager tools)

  1. Molly Brothers
  2. Jasper Rine
(2022)
Distinguishing between recruitment and spread of silent chromatin structures in Saccharomyces cerevisiae
eLife 11:e75653.
https://doi.org/10.7554/eLife.75653

Share this article

https://doi.org/10.7554/eLife.75653

Categories and tags

Research organism

Further reading

    1. Chromosomes and Gene Expression

    Sir2 and Fun30 regulate ribosomal DNA replication timing via MCM helicase positioning and nucleosome occupancy

    Carmina Lichauco, Eric J Foss ... Antonio Bedalov
    Research Article

    The association between late replication timing and low transcription rates in eukaryotic heterochromatin is well known, yet the specific mechanisms underlying this link remain uncertain. In Saccharomyces cerevisiae, the histone deacetylase Sir2 is required for both transcriptional silencing and late replication at the repetitive ribosomal DNA (rDNA) arrays. We have previously reported that in the absence of SIR2, a de-repressed RNA PolII repositions MCM replicative helicases from their loading site at the ribosomal origin, where they abut well-positioned, high-occupancy nucleosomes, to an adjacent region with lower nucleosome occupancy. By developing a method that can distinguish activation of closely spaced MCM complexes, here we show that the displaced MCMs at rDNA origins have increased firing propensity compared to the nondisplaced MCMs. Furthermore, we found that both activation of the repositioned MCMs and low occupancy of the adjacent nucleosomes critically depend on the chromatin remodeling activity of FUN30. Our study elucidates the mechanism by which Sir2 delays replication timing, and it demonstrates, for the first time, that activation of a specific replication origin in vivo relies on the nucleosome context shaped by a single chromatin remodeler.

    1. Chromosomes and Gene Expression

    Cryogenic Electron Microscopy: MagIC beads for scarce macromolecules

    Carlos Moreno-Yruela, Beat Fierz
    Insight

    Specialized magnetic beads that bind target proteins to a cryogenic electron microscopy grid make it possible to study the structure of protein complexes from dilute samples.

    1. Chromosomes and Gene Expression
    2. Structural Biology and Molecular Biophysics

    Surprising features of nuclear receptor interaction networks revealed by live-cell single-molecule imaging

    Liza Dahal, Thomas GW Graham ... Xavier Darzacq
    Research Article

    Type II nuclear receptors (T2NRs) require heterodimerization with a common partner, the retinoid X receptor (RXR), to bind cognate DNA recognition sites in chromatin. Based on previous biochemical and overexpression studies, binding of T2NRs to chromatin is proposed to be regulated by competition for a limiting pool of the core RXR subunit. However, this mechanism has not yet been tested for endogenous proteins in live cells. Using single-molecule tracking (SMT) and proximity-assisted photoactivation (PAPA), we monitored interactions between endogenously tagged RXR and retinoic acid receptor (RAR) in live cells. Unexpectedly, we find that higher expression of RAR, but not RXR, increases heterodimerization and chromatin binding in U2OS cells. This surprising finding indicates the limiting factor is not RXR but likely its cadre of obligate dimer binding partners. SMT and PAPA thus provide a direct way to probe which components are functionally limiting within a complex TF interaction network providing new insights into mechanisms of gene regulation in vivo with implications for drug development targeting nuclear receptors.