The selfish yeast plasmid utilizes the condensin complex and condensed chromatin for faithful partitioning

PLoS Genet. 2021 Jul 16;17(7):e1009660. doi: 10.1371/journal.pgen.1009660. eCollection 2021 Jul.

Abstract

Equipartitioning by chromosome association and copy number correction by DNA amplification are at the heart of the evolutionary success of the selfish yeast 2-micron plasmid. The present analysis reveals frequent plasmid presence near telomeres (TELs) and centromeres (CENs) in mitotic cells, with a preference towards the former. Inactivation of Cdc14 causes plasmid missegregation, which is correlated to the non-disjunction of TELs (and of rDNA) under this condition. Induced missegregation of chromosome XII, one of the largest yeast chromosomes which harbors the rDNA array and is highly dependent on the condensin complex for proper disjunction, increases 2-micron plasmid missegregation. This is not the case when chromosome III, one of the smallest chromosomes, is forced to missegregate. Plasmid stability decreases when the condensin subunit Brn1 is inactivated. Brn1 is recruited to the plasmid partitioning locus (STB) with the assistance of the plasmid-coded partitioning proteins Rep1 and Rep2. Furthermore, in a dihybrid assay, Brn1 interacts with Rep1-Rep2. Taken together, these findings support a role for condensin and/or condensed chromatin in 2-micron plasmid propagation. They suggest that condensed chromosome loci are among favored sites utilized by the plasmid for its chromosome-associated segregation. By homing to condensed/quiescent chromosome locales, and not over-perturbing genome homeostasis, the plasmid may minimize fitness conflicts with its host. Analogous persistence strategies may be utilized by other extrachromosomal selfish genomes, for example, episomes of mammalian viruses that hitchhike on host chromosomes for their stable maintenance.

MeSH terms

  • Adenosine Triphosphatases / genetics*
  • Adenosine Triphosphatases / metabolism
  • Cell Cycle / genetics
  • Cell Cycle Proteins / genetics
  • Cell Division
  • Centromere / metabolism
  • Chromosome Segregation / genetics
  • Chromosomes / genetics
  • DNA Replication / genetics
  • DNA, Fungal / genetics
  • DNA-Binding Proteins / genetics*
  • DNA-Binding Proteins / metabolism
  • Heterochromatin / metabolism
  • Multiprotein Complexes / genetics*
  • Multiprotein Complexes / metabolism
  • Plasmids / genetics*
  • Plasmids / metabolism
  • Repetitive Sequences, Nucleic Acid / genetics
  • Saccharomyces cerevisiae / genetics
  • Saccharomyces cerevisiae Proteins / genetics
  • Saccharomycetales / genetics*
  • Saccharomycetales / metabolism
  • Telomere / metabolism
  • Trans-Activators / genetics

Substances

  • Cell Cycle Proteins
  • DNA, Fungal
  • DNA-Binding Proteins
  • Heterochromatin
  • Multiprotein Complexes
  • Saccharomyces cerevisiae Proteins
  • Trans-Activators
  • condensin complexes
  • Adenosine Triphosphatases

Grants and funding

This work was funded by DST (SB/SO/BB-0125/2013) and DBT (BT/PR13909/BRB/10/1432/2015) Govt. of India grants to SKG and NSF grants (MCB-1049925 and MCB-1949821) and a Robert F Welch Foundation award (F-1274) to MJ. DK, HKP, AM and PM were supported by DBT (DBT/2018/IIT-B/1059), MHRD (10I30006), CSIR (09/087(0873)/2017-EMR-I) and UGC (17-06/2012(i) EU-V) Government of India fellowships, respectively. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.