Yeast heterochromatin is a dynamic structure that requires silencers continuously

Tzu Hao Cheng, Marc R. Gartenberg

Research output: Contribution to journalArticlepeer-review

99 Scopus citations

Abstract

Transcriptional silencing of the HM loci in yeast requires cis-acting elements, termed silencers, that function during S-phase passage to establish the silent state. To study the role of the regulatory elements in maintenance of repression, site-specific recombination was used to uncouple preassembled silent chromatin fragments from silencers. DNA rings excised from HMR were initially silent but ultimately reactivated, even in G1- or G2/M-arrested cells. In contrast, DNA rings bearing HML-derived sequence were stably repressed due to the presence of a protosilencing element. These data show that silencers (or protosilencers) are required continuously for maintenance of silent chromatin. Reactivation of unstably repressed rings was blocked by overexpression of silencing proteins Sir3p and Sir4p, and chromatin immunoprecipitation studies showed that overexpressed Sir3p was incorporated into silent chromatin. Importantly, the protein was incorporated even when expressed outside of S phase, during G1 arrest. That silencing factors can associate with and stabilize preassembled silent chromatin in non-S-phase cells demonstrates that heterochromatin in yeast is dynamic.

Original languageEnglish (US)
Pages (from-to)452-463
Number of pages12
JournalGenes and Development
Volume14
Issue number4
StatePublished - 2000

All Science Journal Classification (ASJC) codes

  • Genetics
  • Developmental Biology

Keywords

  • Heterochromatin
  • Mating- type locus
  • Saccharomyces cerevisiae
  • Silencers
  • Sir proteins
  • Transcriptional repression

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