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5-Bromodeoxyuridine (BrdU) modulates the expression of particular genes associated with cellular differentiation and senescence when incorporated into DNA instead of thymidine (dThd). To date, a molecular mechanism for this phenomenon remains a mystery in spite of a large number of stud-ies. | ỊFEBS Journal 5-Bromodeoxyuridine induces transcription of repressed genes with disruption of nucleosome positioning Kensuke Miki1 Mitsuhiro Shimizu2 Michihiko Fujii1 Shinichi Takayama1 Mohammad Nazir Hossain1 and Dai Ayusawa1 1 Department of Genome System Science Yokohama City University Yokohama Kanagawa Japan 2 Department of Chemistry Meisei University Hino Tokyo Japan Keywords AT-tract 5-bromodeoxyuridine BAR1 nucleosome positioning transcriptional derepression Correspondence D. Ayusawa Department of Genome System Science Yokohama City University Seto 22-2 Kanazawa-Ku Yokohama Kanagawa 236-0027 Japan Fax 81 45 787 2193 Tel 81 45 787 2193 E-mail dayusawa@yokohama-cu.ac.jp Received 5 January 2010 revised 2 August 2010 accepted 2 September 2010 doi 10.1111 j.1742-4658.2010.07868.x 5-Bromodeoxyuridine BrdU modulates the expression of particular genes associated with cellular differentiation and senescence when incorporated into DNA instead of thymidine dThd . To date a molecular mechanism for this phenomenon remains a mystery in spite of a large number of studies. Recently we have demonstrated that BrdU disrupts nucleosome positioning on model plasmids mediated by specific AT-tracts in yeast cells. Here we constructed a cognate plasmid that can form an ordered array of nucleosomes determined by an a2 operator and contains the BAR1 gene as an expression marker gene to examine BAR1 expression in dThd-auxotro-phic MATa cells under various conditions. In medium containing dThd BAR1 expression was completely repressed associated with the formation of the stable array of nucleosomes. Insertion of AT-tracts into a site of the promoter region slightly increased BAR1 expression and slightly destabilized nucleosome positioning dependent on their sequence specificity. In medium containing BrdU BAR1 expression was further enhanced associated with more marked disruption of nucleosome positioning on the promoter region. Disruption of nucleosome positioning seems to be sufficient
