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  • Title: The molecular mechanism regulating the autonomous circadian expression of Topoisomerase I in NIH3T3 cells.
    Author: Yang F, Nakajima Y, Kumagai M, Ohmiya Y, Ikeda M.
    Journal: Biochem Biophys Res Commun; 2009 Feb 27; 380(1):22-7. PubMed ID: 19138663.
    Abstract:
    To identify whether Topoisomerase I (TopoI) has autonomous circadian rhythms regulated by clock genes, we tested mouse TopoI (mTopoI) promoter oscillation in NIH3T3 cells using a real-time monitoring assay and TopoI mRNA oscillations using real-time RT-PCR. Analysis of the mTopoI promoter region with Matlnspector software revealed two putative E-box (E1 and E2) and one DBP/E4BP4-binding element (D-box). Luciferase assays indicated that mTopoI gene expression was directly regulated by clock genes. The real-time monitoring assay showed that E-box and D-box response elements participate in the regulation of the circadian expression of mTopoI. Furthermore, a gel-shift assay showed that E2 is a direct target of the BMAL1/CLOCK heterodimer and DBP binds to the putative D-site. These results indicate that TopoI is expressed in an autonomous circadian rhythm in NIH3T3 cells.
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