Book of Abstracts: Albany 2003
June 17-21 2003
The Mu Transposition Enhancer and Path of DNA within the Mu Transpososome
High-order nucleoprotein complexes direct the execution of various cellular DNA processes such as replication, transcription, repair, recombination and segregation. Several of these transactions involve the recruitment of distant or noncontiguous DNA sites. Their characterization has relied upon lower resolution genetic, biochemical and physical methods such as deletion analysis, footprinting experiments or electron microscopy. Results thus obtained are subject to the caveat that the assembled structures may not represent their native states because of the genetic manipulations imposed on them or the invasive nature of the procedures employed to probe them. We have recently described a more benign ?difference topology? assay that revealed the organization of a three-site DNA synapse involved in phage Mu transposition (1).
The phage Mu transpososome is assembled by interactions of transposase subunits with the left (L) and right (R) ends of Mu and an enhancer (E) located in between. The enhancer is required for the assembly of the active transposase tetramer, and is not needed for the chemistry of transposition. Using ?difference topology?, we have now followed the order and dynamics of association of the L, E, and R sites within a series of transpososomes, from initiation to completion of DNA transposition. Our results suggest a clear-cut hierarchy in the interaction of the enhancer and the two Mu ends, and raise new questions about the role of enhancer post-assembly.
Microbiology and Institute of Cellular and Molecular Biology