DNA sequence selectivity of human topoisomerase I‐mediated DNA cleavage induced by camptothecin |
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Authors: | Chandanamali Punchihewa Megan Carver Danzhou Yang |
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Affiliation: | 1. College of Pharmacy, The University of Arizona, Tucson, Arizona 85721;2. Arizona Cancer Center, Tucson, Arizona 85724;3. BIO5 Institute, The University of Arizona, Tucson, Arizona 85721 |
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Abstract: | In probing the mechanism of inhibition of hypoxia inducible factor (HIF-1) by campothecins, we investigated the ability of human topoisomerase I to bind and cleave HIF-1 response element (HRE), which contains the known camptothecin-mediated topoisomerase I cleavage site 5′-TG. We observed that the selection of 5′-TG by human topoisomerase I and topotecan depends to a large extent on the specific flanking sequences, and that the presence of a G at the −2 position (where cleavage occurs between −1 and +1) prevents the HRE site from being a preferred site for such cleavage. Furthermore, the presence of −2 T/A can induce the cleavage at a less preferred TC or TA site. However, in the absence of a more preferred site, the HRE site is shown to be cleaved by human topoisomerase I in the presence of topotecan. Thus, it is implied that the −2 base has a significant influence on the selection of the camptothecin-mediated Topo I cleavage site, which can overcome the preference for +1G. While the cleavage site recognition has been known to be based on the concerted effect of several bases spanning the cleavage site, such a determining effect of an individual base has not been previously recognized. A possible base-specific interaction between DNA and topoisomerase I may be responsible for this sequence selectivity. |
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Keywords: | human topoisomerase I camptothecin DNA cleavage site HIF‐1 response element |
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