JB Accepts, published online ahead of print on 11 May 2007

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J. Bacteriol. doi:10.1128/JB.00234-07
Copyright (c) 2007, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

A functional homing endonuclease in the Bacillus anthracis nrdE group I intron

David Nord, Eduard Torrents, and Britt-Marie Sjöberg^*

Department of Molecular Biology & Functional Genomics, Stockholm University, SE-10691 Stockholm, Sweden

^* To whom correspondence should be addressed. Email: britt-marie.sjoberg{at}molbio.su.se.

The essential Bacillus anthracis nrdE gene carries a self-splicing group I intron with a putative homing endonuclease belonging to the GIY-YIG family. Here we show that the nrdE pre-mRNA is spliced and that the homing endonuclease cleaves an intron-less nrdE gene 5 nt upstream of the intron insertion site producing 2-nt 3' extensions. We also show that the sequence required for efficient cleavage spans at least 4 bp upstream and 31 bp downstream of the cleaved coding strand. The position of the recognition sequence in relation to the cleavage position is as expected for a GIY-YIG homing endonuclease. Interestingly, nrdE genes from several other Bacillaceae were also susceptible to cleavage, with B. cereus, Staphylococcus epidermidis (nrdE1), B. anthracis and B. thuringiensis konkukian being better substrates than B. subtilis, B. lichenformis and S. epidermidis (nrdE2). On the other hand, nrdE genes from Lactococcus lactis, Escherichia coli, Salmonella typhimurium and Corynebacterium ammoniagenes were not cleaved. Intervening sequences (IVS) residing in protein-coding genes are often found in enzymes involved in DNA metabolism, and the ribonucleotide reductase nrdE gene is a frequent target for self-splicing IVSs. A comparison of nrdE genes from seven Gram-positive low GC bacteria, two bacteriophages, and Nocardia farcinica shows five different insertion sites for self-splicing IVSs within the coding region of the nrdE gene.

This article has been cited by other articles:

• Tourasse, N. J., Kolsto, A.-B. (2008). Survey of group I and group II introns in 29 sequenced genomes of the Bacillus cereus group: insights into their spread and evolution. Nucleic Acids Res 36: 4529-4548 [Abstract] [Full Text]  
• Nord, D., Sjoberg, B.-M. (2008). Unconventional GIY-YIG homing endonuclease encoded in group I introns in closely related strains of the Bacillus cereus group. Nucleic Acids Res 36: 300-310 [Abstract] [Full Text]