Genome-Organizing Factors Top2 and Hmo1 Prevent Chromosome Fragility at Sites of S phase Transcription

Rodrigo Bermejo, Thelma Capra, Victor Gonzalez-Huici, Daniele Fachinetti, Andrea Cocito, Gioacchino Natoli, Yuki Katou, Hiroshi Mori, Ken Kurokawa, Katsuhiko Shirahige, Marco Foiani

Research output: Contribution to journalArticlepeer-review


Specialized topoisomerases solve the topological constraints arising when replication forks encounter transcription. We have investigated the contribution of Top2 in S phase transcription. Specifically in S phase, Top2 binds intergenic regions close to transcribed genes. The Top2-bound loci exhibit low nucleosome density and accumulate γH2A when Top2 is defective. These intergenic loci associate with the HMG protein Hmo1 throughout the cell cycle and are refractory to the histone variant Htz1. In top2 mutants, Hmo1 is deleterious and accumulates at pericentromeric regions in G2/M. Our data indicate that Top2 is dispensable for transcription and that Hmo1 and Top2 bind in the proximity of genes transcribed in S phase suppressing chromosome fragility at the M-G1 transition. We propose that an Hmo1-dependent epigenetic signature together with Top2 mediate an S phase architectural pathway to preserve genome integrity.

Original languageEnglish
Pages (from-to)870-884
Number of pages15
Issue number5
Publication statusPublished - Sep 4 2009


  • DNA

ASJC Scopus subject areas

  • Biochemistry, Genetics and Molecular Biology(all)


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