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PLoS Genet. 2011 Jan 20;7(1):e1001277. doi: 10.1371/journal.pgen.1001277.

The transposon-like Correia elements encode numerous strong promoters and provide a potential new mechanism for phase variation in the meningococcus.

Author information

1
School of Biomedical Sciences, University of Nottingham, Queen's Medical Centre, Nottingham, United Kingdom.

Abstract

Neisseria meningitidis is the primary causative agent of bacterial meningitis. The genome is rich in repetitive DNA and almost 2% is occupied by a diminutive transposon called the Correia element. Here we report a bioinformatic analysis defining eight subtypes of the element with four distinct types of ends. Transcriptional analysis, using PCR and a lacZ reporter system, revealed that two ends in particular encode strong promoters. The activity of the strongest promoter is dictated by a recurrent polymorphism (Y128) at the right end of the element. We highlight examples of elements that appear to drive transcription of adjacent genes and others that may express small non-coding RNAs. Pair-wise comparisons between three meningococcal genomes revealed that no more than two-thirds of Correia elements maintain their subtype at any particular locus. This is due to recombinational class switching between elements in a single strain. Upon switching subtype, a new allele is available to spread through the population by natural transformation. This process may represent a hitherto unrecognized mechanism for phase variation in the meningococcus. We conclude that the strain-to-strain variability of the Correia elements, and the large number of strong promoters encoded by them, allows for potentially widespread effects within the population as a whole. By defining the strength of the promoters encoded by the eight subtypes of Correia ends, we provide a resource that allows the transcriptional effects of a particular subtype at a given locus to be predicted.

PMID:
21283790
PMCID:
PMC3024310
DOI:
10.1371/journal.pgen.1001277
[Indexed for MEDLINE]
Free PMC Article

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