title: Isolation and functional analysis of the 5'-flanking region of carrot top1beta gene coding for the beta isoform of DNA topoisomerase I.
abstract: We have isolated and functionally characterized the promoter region of the top1beta gene encoding carrot (Daucus carota) DNA topoisomerase Ibeta. The major transcription start site was mapped by primer extension analysis 164 nt upstream the ATG translation start codon. Sequence analysis of the 5'-upstream region of the gene revealed the presence of a canonical TATA-like box at position -35 bp and several cis-acting sequences, including a (CT)n element in the leader region of the gene, a myb-related motif and the Dof element NtBBF-1, which correlate with the inducible expression pattern of this gene. Functional reporter analysis of the top1beta 5'-flanking region was performed in both carrot and Arabidopsis thaliana transfected protoplasts. The region at -719 to +161 was sufficient to confer high expression level in both species. The transient expression assay in protoplasts induced to stop dividing confirmed that the promoter, whose activity is low in quiescent cells, is activated when protoplasts are induced to proliferate by exogenous application of growth factors.
authors.affiliation: Department of Genetics and Microbiology, University of Pavia, A. Buzzati-Traverso, Via Ferrata 1, Via Abbiategrasso 207, 27100 Pavia, Italy.
authors.forename: Alma
authors.initials: A
authors.lastname: Balestrazzi
authors.forename: Valentina
authors.initials: V
authors.lastname: Ressegotti
authors.forename: Laura
authors.initials: L
authors.lastname: Panzarasa
authors.forename: Daniela
authors.initials: D
authors.lastname: Carbonera
mesh_terms: D024506:5' Flanking Region / Q000502:physiology*; D001483:Base Sequence; D001665:Binding Sites; D002467:Cell Nucleus / Q000378:metabolism; D002478:Cells, Cultured; D003001:Cloning, Molecular; D004264:DNA Topoisomerases, Type I / Q000235:genetics*; D018552:Daucus carota / Q000235:genetics*; D017353:Gene Deletion; D017930:Genes, Reporter; D007527:Isoenzymes / Q000235:genetics; D008969:Molecular Sequence Data; D014674:Plant Proteins, Dietary / Q000235:genetics*; D011523:Protoplasts / Q000378:metabolism; D012045:Regulatory Sequences, Nucleic Acid; D024363:Transcription Initiation Site
chemical_list: D007527:Isoenzymes; D014674:Plant Proteins, Dietary; D004264:DNA Topoisomerases, Type I