Nucleic Acids Research Advance Access originally published online on March 11, 2008
Nucleic Acids Research 2008 36(8):2581-2593; doi:10.1093/nar/gkn097
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Nucleic Acids Research, 2008, Vol. 36, No. 8 2581-2593
© 2008 The Author(s)
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/2.0/uk/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Nucleic Acid Enzymes |
Real-time kinetics of restriction–modification gene expression after entry into a new host cell
1Department of Medical Microbiology and Immunology, University of Toledo Health Sciences Campus, Toledo, OH 43614-2598, USA, 2Department of Microbiology, University of Gdansk, Gdansk, 80-822, Poland and 3Program in Bioinformatics and Proteomics/Genomics, University of Toledo Health Sciences Campus, Toledo, OH 43614-2598, USA
*To whom correspondence should be addressed. Tel: +1 419 383 5422; Fax: +1 419 383 3002; Email: robert.blumenthal{at}utoledo.edu Correspondence may also be addressed to Iwona Mruk. Tel: +1 419 383 4014; Fax: +1 419 383 3002; Email: Iwona.Mruk{at}utoledo.edu
Received December 10, 2007. Revised February 15, 2008. Accepted February 20, 2008.
Most type II restriction–modification (R–M) systems produce separate restriction endonuclease (REase) and methyltransferase (MTase) proteins. After R–M system genes enter a new cell, protective MTase must appear before REase to avoid host chromosome cleavage. The basis for this apparent temporal regulation is not well understood. PvuII and some other R–M systems appear to achieve this delay by cotranscribing the REase gene with the gene for an autogenous transcription activator/repressor (the ‘C’ protein C.PvuII). To test this model, bacteriophage M13 was used to introduce the PvuII genes into a bacterial population in a relatively synchronous manner. REase mRNA and activity appeared 
10 min after those of the MTase, but never rose if there was an inactivating pvuIIC mutation. Infection with recombinant M13pvuII phage had little effect on cell growth, relative to infection with parental M13. However, infection of cells pre-expressing C.PvuII led to cessation of growth. This study presents the first direct demonstration of delayed REase expression, relative to MTase, when type II R–M genes enter a new host cell. Surprisingly, though the C and REase genes are cotranscribed, the pvuIIC portion of the mRNA was more abundant than the pvuIIR portion after stable establishment of the R–M system.