| Literature DB >> 2541429 |
G Camilloni1, E Di Martino, E Di Mauro, M Caserta.
Abstract
The effects of supercoiling on the cleavage reaction by eukaryotic DNA topoisomerases I (wheat germ, chicken erythrocyte, and calf thymus) have been analyzed on DNA fragments (0.96 and 2.3 kilobases) encompassing an immunoglobulin kappa light-chain promoter. In one topological condition of the substrate, the absolutely relaxed state, cleavage was found to be impeded. This finding defines the topology-dependent step of the eukaryotic DNA topoisomerase I reaction and shows that for the cleavage reaction topology is more critical than sequence effects. These findings suggest a simple model for the regulation of the DNA topoisomerase I reaction based on topological factors, which may explain the regulatory function of the enzyme in in vivo eukaryotic transcription.Entities:
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Year: 1989 PMID： 2541429 PMCID： PMC287068 DOI： 10.1073/pnas.86.9.3080
Source DB: PubMed Journal: Proc Natl Acad Sci U S A ISSN： 0027-8424 Impact factor: 11.205