William S. Reznikoff

Biochemical genetics; studies on the molecular mechanism of transposition

Transposition is a complex genetic rearrangement process found in all organisms. Transposition is involved in genome evolution, with the spread of antibiotic resistance in bacteria, and with chromosome changes found in some cancers. Transposition is biochemically very similar to the HIV-1 provirus integration reaction. In addition, transposition is likely to offer new tools for rearranging DNA molecules in the laboratory. Thus, this process is of considerable interest.

My laboratory is deciphering the molecular details of transposition by studying a model bacterial transposon, Tn5. Tn5 encodes a protein called a transposase that catalyzes all the steps in transposition; transposase-transposon DNA binding, formation of a transposon nucleoprotein complex, cleavage of the transposon DNA free from surrounding DNA sequences, insertion of the transposon DNA into a new genetic site. For Tn5, all of these steps occur in a simple, defined, in vitro system. This allows us to study the detailed biochemical effects of various transposase and DNA target site mutations. In addition, we have, with the collaboration of Professor Ivan Rayment’s laboratory, determined the three-dimensional structure of the transposase. This, coupled with the genetics and biochemistry, will generate a complete structure/function picture of the transposase and its target DNA sequences.

My laboratory is also interested in developing the Tn5 transposition system as a molecular genetic tool. Our long term goal is to develop methods that would allow in vitro combinatorial genetics to become a standard laboratory procedure.

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