title: Expression of the topoisomerase I gene in serum stimulated human fibroblasts.
abstract: We have determined the levels of mRNA coding for human type I DNA topoisomerase (EC 5.99.1.2.) in resting and proliferating human cells in culture. After addition of serum to growth arrested cells, we observed an continuous increase in the amount of topoisomerase I mRNA, starting after serum addition and reaching a maximum at 25 h after stimulation. At the end of the S-phase, a 6-fold higher amount of topoisomerase I mRNA was present in these cells. Nuclear run on transcription experiments showed, that the increase of topoisomerase I mRNA was preceded by a 3- to 4-fold increase in de novo mRNA synthesis. In contrast, during the same time period the amount of topoisomerase I increased only by a factor of 2, and the specific activity (enzymatic activity/mg protein) remained constant.
authors.affiliation: University of Konstanz, Department of Biology.
authors.forename: H
authors.initials: H
authors.lastname: Romig
authors.forename: A
authors.initials: A
authors.lastname: Richter
mesh_terms: D000818:Animals; D001769:Blood; D002455:Cell Division; D002460:Cell Line; D002467:Cell Nucleus / Q000201:enzymology; D003470:Culture Media; D004264:DNA Topoisomerases, Type I / Q000235:genetics* / Q000378:metabolism; D005347:Fibroblasts / Q000166:cytology / Q000201:enzymology; D005786:Gene Expression Regulation; D005796:Genes; D006801:Humans; D007700:Kinetics; D012333:RNA, Messenger / Q000235:genetics; D014158:Transcription, Genetic
chemical_list: D003470:Culture Media; D012333:RNA, Messenger; D004264:DNA Topoisomerases, Type I