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J. Bacteriol. doi:10.1128/JB.01408-06
Copyright (c) 2006, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

A new functional identity for the DNA uptake sequence in transformation and its presence in transcriptional terminators

Centre for Molecular Biology and Neuroscience and Institute of Microbiology, University of Oslo, and Rikshospitalet-Radiumhospitalet Medical Center, NO-0027 Oslo, Norway

^* To whom correspondence should be addressed. Email: tone.tonjum{at}medisin.uio.no.

	Abstract

The frequently occurring DNA uptake sequence (DUS), recognized as a 10 base pair repeat, is required for efficient genetic transformation in the human pathogens Neisseria meningitidis and Neisseria gonorrhoeae. Genome scanning for DUS occurrences in three different species of Neisseria demonstrated that 76% of the nearly 2000 neisserial DUS were found to have two semi-conserved base pairs extending from the 5' end of DUS to constitute a 12-mer repeat. Plasmids containing sequential variants of the neisserial DUS were tested for their ability to transform N. meningitidis and N. gonorrhoeae and the 12-mer was found to outperform the 10-mer DUS in transformation efficiency. Assessment of meningococcal uptake of DNA confirmed the enhanced performance of the 12-mer as compared to the 10-mer DUS. Inverted repeat DUS was not more efficient in transformation than DNA species containing a single or direct repeat DUS. Genome-wide analysis revealed that half of the nearly 1500 12-mer DUS are arranged as inverted repeats predicted to be involved in rho-independent transcriptional termination or attenuation. The distribution of the uptake signal sequence (USS) required for transformation in the Pasteurellaceae was also biased towards transcriptional terminators, although to a lesser extent. In addition to assessing the intergenic location of DUS, we propose that the 10-mer identity of DUS should be extended and recognized as a 12-mer DUS. The dual role of DUS in transformation and comprising a structural component on RNA affecting transcription makes this a relevant model system for assessing significant roles of repeat sequences in biology.

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