Overexpression of RNase H partially complements the growth defect of an Escherichia coli delta topA mutant: R-loop formation is a major problem in the absence of DNA topoisomerase I.
AUTOR(ES)
Drolet, M
RESUMO
Previous biochemical studies have suggested a role for bacterial DNA topoisomerase (TOPO) I in the suppression of R-loop formation during transcription. In this report, we present several pieces of genetic evidence to support a model in which R-loop formation is dynamically regulated during transcription by activities of multiple DNA TOPOs and RNase H. In addition, our results suggest that events leading to the serious growth problems in the absence of DNA TOPO I are linked to R-loop formation. We show that the overexpression of RNase H, an enzyme that degrades the RNA moiety of an R loop, can partially compensate for the absence of DNA TOPO I. We also note that a defect in DNA gyrase can correct several phenotypes associated with a mutation in the rnhA gene, which encodes the major RNase H activity. In addition, we found that a combination of topA and rnhA mutations is lethal.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=42200Documentos Relacionados
- Escherichia coli RecG and RecA proteins in R-loop formation.
- RecA protein-dependent R-loop formation in vitro
- Transcription-dependent R-loop formation at mammalian class switch sequences
- Double stranded scission of DNA directed through sequence-specific R-loop formation.
- The Escherichia coli supX locus is topA, the structural gene for DNA topoisomerase I.