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DNA sequence selectivity of human topoisomerase I‐mediated DNA cleavage induced by camptothecin
Author(s) -
Punchihewa Chandanamali,
Carver Megan,
Yang Danzhou
Publication year - 2009
Publication title -
protein science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.353
H-Index - 175
eISSN - 1469-896X
pISSN - 0961-8368
DOI - 10.1002/pro.138
Subject(s) - topoisomerase , cleavage (geology) , camptothecin , dna , binding site , cleavage factor , biology , base pair , pbr322 , topotecan , chemistry , stereochemistry , microbiology and biotechnology , biochemistry , gene , genetics , plasmid , rna , paleontology , chemotherapy , fracture (geology)
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.