Negative supercoil at gene boundaries modulates gene topology

Nature. 2020 Jan;577(7792):701-705. doi: 10.1038/s41586-020-1934-4. Epub 2020 Jan 22.


Transcription challenges the integrity of replicating chromosomes by generating topological stress and conflicts with forks1,2. The DNA topoisomerases Top1 and Top2 and the HMGB family protein Hmo1 assist DNA replication and transcription3-6. Here we describe the topological architecture of genes in Saccharomyces cerevisiae during the G1 and S phases of the cell cycle. We found under-wound DNA at gene boundaries and over-wound DNA within coding regions. This arrangement does not depend on Pol II or S phase. Top2 and Hmo1 preserve negative supercoil at gene boundaries, while Top1 acts at coding regions. Transcription generates RNA-DNA hybrids within coding regions, independently of fork orientation. During S phase, Hmo1 protects under-wound DNA from Top2, while Top2 confines Pol II and Top1 at coding units, counteracting transcription leakage and aberrant hybrids at gene boundaries. Negative supercoil at gene boundaries prevents supercoil diffusion and nucleosome repositioning at coding regions. DNA looping occurs at Top2 clusters. We propose that Hmo1 locks gene boundaries in a cruciform conformation and, with Top2, modulates the architecture of genes that retain the memory of the topological arrangements even when transcription is repressed.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Chromatin Assembly and Disassembly
  • DNA Replication
  • DNA Topoisomerases, Type I / metabolism
  • DNA Topoisomerases, Type II / genetics
  • DNA Topoisomerases, Type II / metabolism
  • DNA, Cruciform / chemistry
  • DNA, Cruciform / genetics
  • DNA, Cruciform / metabolism
  • DNA, Fungal / chemistry*
  • DNA, Fungal / genetics
  • DNA, Fungal / metabolism
  • DNA, Superhelical / chemistry*
  • DNA, Superhelical / genetics
  • DNA, Superhelical / metabolism
  • G1 Phase
  • Gene Expression Regulation, Fungal
  • Genes, Fungal*
  • High Mobility Group Proteins / metabolism
  • Mutation
  • Nucleic Acid Hybridization
  • Nucleosomes / chemistry
  • Nucleosomes / genetics
  • Nucleosomes / metabolism
  • Open Reading Frames / genetics
  • RNA Polymerase II / genetics
  • RNA Polymerase II / metabolism
  • RNA, Fungal / chemistry
  • RNA, Fungal / genetics
  • RNA, Fungal / metabolism
  • S Phase
  • Saccharomyces cerevisiae / cytology*
  • Saccharomyces cerevisiae / enzymology
  • Saccharomyces cerevisiae / genetics*
  • Saccharomyces cerevisiae Proteins / metabolism
  • Transcription, Genetic


  • DNA, Cruciform
  • DNA, Fungal
  • DNA, Superhelical
  • HMO1 protein, S cerevisiae
  • High Mobility Group Proteins
  • Nucleosomes
  • RNA, Fungal
  • Saccharomyces cerevisiae Proteins
  • TOP2 protein, S cerevisiae
  • RNA Polymerase II
  • TOP1 protein, S cerevisiae
  • DNA Topoisomerases, Type I
  • DNA Topoisomerases, Type II