Nucleosomes represent a physical barrier for cleavage activity of DNA topoisomerase I in vivo.
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.
Di Felice
Francesca
F
Dipartimento di Genetica e Biologia Molecolare Università di Roma La Sapienza, Roma, 00185 Italy.
Chiani
Francesco
F
Camilloni
Giorgio
G
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
D002843:Chromatin; D009707:Nucleosomes; D004247:DNA; D004264:DNA Topoisomerases, Type I