2Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, 119991 Moscow, Russia; E-mail: firstname.lastname@example.org
* To whom correspondence should be addressed.
Received January 13, 2011; Revision received February 14, 2011
Endonuclease WEN1 with apparent molecular mass about 27 kDa isolated from cytoplasmic vesicular fraction of aging coleoptiles of wheat seedlings has expressed site specificity action. This is a first detection and isolation of a site-specific endonuclease from higher eukaryotes, in general, and higher plants, in particular. The enzyme hydrolyzes deoxyribooligonucleotides of different composition on CNG (N is G, A, C, or T) sites by splitting the phosphodiester bond between C and N nucleotide residues in CNG sequence independent from neighbor nucleotide context except for CCCG. WEN1 prefers to hydrolyze methylated λ phage DNA and double-stranded deoxyribooligonucleotides containing 5-methylcytosine sites (m5CAG, m5CTG) compared with unmethylated substrates. The enzyme is also able to hydrolyze single-stranded substrates, but in this case it splits unmethylated substrates predominantly. Detection in wheat seedlings of WEN1 endonuclease that is site specific, sensitive to the substrate methylation status, and modulated with S-adenosyl-L-methionine indicates that in higher plants restriction–modification systems or some of their elements, at least, may exist.
KEY WORDS: 5-methylcytosine, AdoMet, CNG site, evolution, mitochondria, plant endonuclease, site specific action, wheat