Book of Abstracts: Albany 2011
June 14-18 2011
©Adenine Press (2010)
Strand Exchange Reaction Between Short Oligonucleotides Promoted by a Derivative of 1,3 – diazaadamantane.
The DNA strand exchange reaction (SER) underlies main pathways of homologous recombination (HR) and DNA repair in different organisms. These systems of DNA metabolism closely relate to carcinogenesis and better understanding of interaction of antitumor drugs with their components is indispensable for development of new approaches to antitumor therapy. Recently this Journal has reported antitumor intercalators and groove binders interacting with DNA double helix (1-3).
Derivatives of 1,3-diazaadamantane are promising compounds that possess essential antitumor activity on different types of experimental tumors (4). In the present study the interaction of the 1,3-diazaadamantane derivative HG122 (Fig. 1) [1′--benzil-5,7-dipropil-6-oxyspiro(1,3– diazaadamantane-2,4′-piperidine)] with DNA and its behavior in the system that simulate SER has been characterized.
Earlier we described an experimental system for the study of SER between short oligonucleotides promoted by RecA protein from ε.coli and RecA-like human recombinases (6). RecA protein is a paradigm of the wide class of proteins of HR systems from different organisms and promotes the central stage of HR – DNA strand exchange. In our system fluorescent dye-tagged 21-mer oligonucleotide and unlabelled double stranded 21 bp oligonucleotides were used as single- and double stranded substrates of SER respectively.
We did not detect any influence of HG122 on the RecA protein promoted DNA strand exchange. At the same time, it was revealed that this compound by itself exhibited the capability to facilitate SER in this system. Kinetic curves of the SER in solution with different concentrations of Hg122 were obtained for various temperatures. The final yield of SER didn't depend on temperature in the range from 28 to 50oC that argues in favor of thermodynamics equilibrium reached by this reaction. In separate experiments we found no effect of HG 122 on the melting temperature of double-stranded DNA; therefore, the observed acceleration of SER in the presence of HG122 can not be explained by trivial effect of destabilization of the DNA double helix.
Earlier, the DNA strand exchange activity was documented for Cationic Comb-type Copolymers (6) and positively charged liposome surfaces (7). We found that other polycations such as linker histones and cobalt hexamine also exhibit the capability to promote SER (manuscript in preparation). The present results provide us with the first example of the quite different class of SER facilitating compounds that contain large lipophilic core.
Common feature of the strand exchange reactions promoted by polycationic agents is their low tolerance to heterology between the SER substrates. In contrast to the reactions promoted by RecA-like proteins that exhibit increased tolerance to heterology between the substrates (5) the tolerance of polycations promoted strand exchange is comparable to that of the spontaneous SER that proceeds at elevated temperatures. Hg122 promoted reaction exhibits the tolerance to heterology intermediate between the cases of the SER promoted by polycations and RecA-like proteins.
Therefore, the present results demonstrate that Hg122 exhibits interesting behavior and can serve as a model object for further studies of different aspects of DNA strand exchange reaction. Biomedical implications of this and other similar compounds activities remain to be estimated.
1Research-technological Center of Organic & Pharmacological Chemistry (Armenian National Academy of Sciences), 26 Azatutian Avenue, 0014, Armenia.