The long-term goal of our research is the analysis
of structure and function of eukaryotic chromosomes.
The current research activity is focused on the structure,
function and mechanism of DNA topoisomerases, a family
of enzymes which play a critical role in regulating
the structure/function of DNA and chromosomes. DNA
topoisomerases can mediate the DNA structural transition
by reversibly breaking DNA backbone bonds and passing
DNA strands through these transient DNA breaks. The
interest in DNA topoisomerases is also heightened
by the recent discovery that they are the intracellular
pharmacological targets of a number of clinically
important anti-tumor and antibiotic drugs. Therefore,
furthering our understanding of the molecular mechanism
and biological function of DNA topoisomerases is of
immediate relevance to the development of anti-topoisomerase
drugs as chemotherapeutic agents.
The specific aim of the proposed research will encompass
two major areas: structure/function analysis of DNA
topoisomerases and the study of biological functions
of these enzymes. The structural and functional analysis
of DNA topoisomerases are facilitated by efficient
heterologous expression system for both type I and
II enzymes from Drosophila melanogaster. For the type
II DNA topoisomerase, region-specific mutagenesis
will be carried out in a domain which is possibly
involved in coordinating the ATPase function and DNA
breakage/rejoining activity of this enzyme. The availability
of linker-insertional mutants generated in this laboratory
will provide a handle to engineer the protein for
further biochemical analysis. For type I DNA topoisomerase,
we will focus on the analysis of possible biochemical
role of the hydrophilic amino terminus, especially
the effect of phosphorylation on the enzymatic activity.
The biological functions of DNA topoisomerase will
be studied by a molecular genetic approach. There
are a number of new topoisomerase I mutants generated
in our laboratory and they can provide us valuable
tools in defining the critical physiological role
of DNA topoisomerase I during the growth and development
of a multicellular organism. Students participate
in all aspects of the research projects.
