Nucleic Acids Research Advance Access originally published online on July 10, 2009
Nucleic Acids Research 2009 37(16):5322-5330; doi:10.1093/nar/gkp579
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Nucleic Acids Research, 2009, Vol. 37, No. 16 5322-5330
© 2009 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.
Gene Regulation, Chromatin and Epigenetics |
Transcription regulation of restriction-modification system Ecl18kI
1Institute of Biochemistry and Physiology of Microorganisms, Russian Academy of Sciences, Pushchino, 142290 Russia, 2Waksman Institute for Microbiology, Department of Biochemistry and Molecular Biology, Rutgers, the State University of New Jersey, Piscataway, NJ 08854 USA and 3Institutes of Molecular Genetics and Gene Biology, Russian Academy of Sciences, Moscow, Russia
*To whom correspondence should be addressed. Tel: +1 732 445 6095; Fax: +1 732 445 5735; Email: severik{at}waksman.rutgers.edu
Received April 29, 2009. Revised June 23, 2009. Accepted June 23, 2009.
Restriction-modification (R-M) system Ecl18kI is representative of R-M systems whose coordinated transcription is achieved through a separate DNA-binding domain of the methyltransferase. M.Ecl18kI recognizes an operator sequence located in the noncoding region that separates the divergently transcribed R and M genes. Here we show that, contrary to previous predictions, the two ecl18kI promoters are not divergent, but actually face one another. The binding of M.Ecl18kI to its operator prevents RNA polymerase (RNAP) binding to the M promoter by steric exclusion, but has no direct effect on RNAP interaction with the R promoter. The start point for R transcription is located outside of the intergenic region, opposite the initiation codon of the M gene. Regulated transcription of the potentially toxic ecl18kI R gene is accomplished (i) at the stage of promoter complex formation, through direct competition from complexes formed at the M promoter, and (ii) at the stage of promoter clearance, since R promoter-bound RNAP escapes the promoter more slowly than RNAP bound to the M promoter.