RT Journal Article SR Electronic T1 Cloning and Characterization of an Arabidopsis thaliana Topoisomerase I Gene JF Plant Physiology JO Plant Physiol. FD American Society of Plant Biologists SP 1493 OP 1501 DO 10.1104/pp.99.4.1493 VO 99 IS 4 A1 Kieber, Joseph J. A1 Tissier, Alain F. A1 Signer, Ethan R. YR 1992 UL http://www.plantphysiol.org/content/99/4/1493.abstract AB cDNA and genomic clones encoding DNA topoisomerase I were isolated from Arabidopsis thaliana λgt11 and λFix libraries by low stringency hybridization with a Saccharomyces cerevisiae TOP1 probe. The cDNA clones include a 2748-base pair open reading frame predicting an amino acid sequence that is highly homologous to sequences encoded by TOP1 from yeast and human sources. The sequence of the upstream genomic region reveals two putative TATA-like elements and a purine-rich region, but no other obvious controlling elements. Southern blot analysis shows that the gene is present as a single copy in the Arabidopsis genome. When expressed in a S. cerevisiae top1 mutant under the control of the GAL1 promoter, the gene complements the phenotype caused by loss of topoisomerase activity and directs the expression of a protein that cross-reacts with a human anti-topoisomerase I antibody.