title: Nucleosomes represent a physical barrier for cleavage activity of DNA topoisomerase I in vivo.
abstract: DNA topoisomerase I together with the other cellular DNA topoisomerases releases the torsional stress from DNA caused by processes such as replication, transcription and recombination. Despite the well-defined knowledge of its mechanism of action, DNA topoisomerase I in vivo activity has been only partially characterized. In fact the basic question concerning the capability of the enzyme to cleave and rejoin DNA wrapped around a histone octamer remains still unanswered. By studying both in vivo and in vitro the cleavage activity of DNA topoisomerase I in the presence of camptothecin on a repeated trinucleotide sequence, (TTA)(35), lying in chromosome XIII of Saccharomyces cerevisiae, we can conclude that nucleosomes represent a physical barrier for the enzyme activity.
authors.affiliation: Dipartimento di Genetica e Biologia Molecolare Università di Roma La Sapienza, Roma, 00185 Italy.
authors.forename: Francesca
authors.initials: F
authors.lastname: Di Felice
authors.forename: Francesco
authors.initials: F
authors.lastname: Chiani
authors.forename: Giorgio
authors.initials: G
authors.lastname: Camilloni
mesh_terms: D000818:Animals; D001483:Base Sequence; D002417:Cattle; D002843:Chromatin / Q000235:genetics; D004247:DNA / Q000378:metabolism; D004264:DNA Topoisomerases, Type I / Q000235:genetics / Q000378:metabolism*; D009707:Nucleosomes / Q000235:genetics / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics
chemical_list: D002843:Chromatin; D009707:Nucleosomes; D004247:DNA; D004264:DNA Topoisomerases, Type I