Genome Packaging with a Bow

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Science  16 Nov 2012:
Vol. 338, Issue 6109, pp. 865
DOI: 10.1126/science.338.6109.865-b

The genomes of prokaryotes, like those of eukaryotes, must be carefully condensed to fit into and function within the cells they control. The resultant “nucleoid” structure can be partitioned into four macrodomains (MDs): Ori (containing the replication origin), Right, Left, and Ter (containing the replication termination site). This organization is critical for chromosome segregation during cell division.

Dupaigne et al. analyzed the structure and function of the Macrodomain Ter protein (MatP) from Escherichia coli and Yersinia pestis, which is specifically responsible for Ter MD organization. MatP was composed of three domains. The central domain was required for MatP dimerization. The N-terminal four-helix-bundle domain bound specifically to a DNA consensus sequence, matS, scattered throughout the Ter MD but was not found in any of the other MDs. The C-terminal coiled-coil domain drove association of the DNA-bound MatP dimers into tetramers. The tetramer formed a long rod-shaped complex, with the two DNA binding sites at opposite ends, up to 135 Å apart. The coiled-coil domain could also kink to impart a variety of bend angles to the rod complex and was critical for condensation of the Ter MD DNA, probably through MatP's ability to organize DNA between distant matS sites into loops.

Mol. Cell. 10.1016/j.molcel.2012.09.009 (2012).

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