Topoisomerase I suppresses genomic instability by preventing interference between replication and transcription.

Abstract

Topoisomerase I (Top1) is a key enzyme in functioning at the interface between DNA replication, transcription and mRNA maturation. Here, we show that Top1 suppresses genomic instability in mammalian cells by preventing a conflict between transcription and DNA replication. Using DNA combing and ChIP (chromatin immunoprecipitation)-on-chip, we found that Top1-deficient cells accumulate stalled replication forks and chromosome breaks in S phase, and that breaks occur preferentially at gene-rich regions of the genome. Notably, these phenotypes were suppressed by preventing the formation of RNA-DNA hybrids (R-loops) during transcription. Moreover, these defects could be mimicked by depletion of the splicing factor ASF/SF2 (alternative splicing factor/splicing factor 2), which interacts functionally with Top1. Taken together, these data indicate that Top1 prevents replication fork collapse by suppressing the formation of R-loops in an ASF/SF2-dependent manner. We propose that interference between replication and transcription represents a major source of spontaneous replication stress, which could drive genomic instability during the early stages of tumorigenesis.

• Authors: Sandie Tuduri, Laure Crabbé, Chiara Conti, Hélène Tourrière, Heidi Holtgreve-Grez, Anna Jauch, Véronique Pantesco, John De Vos, Aubin Thomas, Charles Theillet, Yves Pommier, Jamal Tazi, Arnaud Coquelle, Philippe Pasero
• Journal: Nature cell biology (Nat Cell Biol) Vol. 11 Issue 11 Pg. 1315-24 (Nov 2009) ISSN: 1476-4679 [Electronic] England
• PMID: 19838172 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• DNA Topoisomerases, Type I

Topics

• Animals
• Chromatin Immunoprecipitation
• DNA Replication (physiology)
• DNA Topoisomerases, Type I (physiology)
• Genomic Instability (physiology)
• S Phase
• Transcription, Genetic