title: Relaxed specificity of prokaryotic DNA methyltransferases results in DNA site-specific modification of RNA/DNA heteroduplexes.
abstract: RNA/DNA hybrid duplexes regularly occur in nature, for example in transcriptional R loops. Their susceptibility to modification by DNA-specific or RNA-specific enzymes is, thus, a biologically relevant question, which, in addition, has possible biotechnological implications. In this study, we investigated the activity of four isospecific DNA methyltransferases (M.EcoVIII, M.LlaCI, M.HindIII, M.BstZ1II) toward an RNA/DNA duplex carrying one 5'-AAGCUU-3'/3'-TTCGAA-5' target sequence. The analyzed enzymes belong to the β-group of adenine N6-methyltransferases and recognize the palindromic DNA sequence 5'-AAGCTT-3'/3'-TTCGAA-5'. Under standard conditions, none of these isospecific enzymes could detectibly methylate the RNA/DNA duplex. However, the addition of agents that generally relax specificity, such as dimethyl sulfoxide (DMSO) and glycerol, resulted in substantial methylation of the RNA/DNA duplex by M.EcoVIII and M.LlaCI. Only the DNA strand of the RNA/DNA duplex was methylated. The same was not observed for M.HindIII or M.BstZ1II. This is, to our knowledge, the first report that demonstrates such activity by prokaryotic DNA methyltransferases. Possible applications of these findings in a laboratory practice are also discussed.
authors: Department of Microbiology, University of Gdansk, Wita Stwosza 59, 80-308, Gdansk, Poland.
authors: Ewa
authors: E
authors: Wons
authors: Department of Microbiology, University of Gdansk, Wita Stwosza 59, 80-308, Gdansk, Poland.
authors: Iwona
authors: I
authors: Mruk
authors: Department of Microbiology, University of Gdansk, Wita Stwosza 59, 80-308, Gdansk, Poland. tadeusz.kaczorowski@biol.ug.edu.pl.
authors: Tadeusz
authors: T
authors: Kaczorowski
mesh_terms: D001419:Bacteria / Q000201:enzymology*; D001426:Bacterial Proteins / Q000737:chemistry; D004247:DNA / Q000737:chemistry; D015254:DNA Modification Methylases / Q000737:chemistry*; D009692:Nucleic Acid Heteroduplexes / Q000737:chemistry*; D012313:RNA / Q000737:chemistry; D013379:Substrate Specificity
chemical_list: D001426:Bacterial Proteins; D009692:Nucleic Acid Heteroduplexes; D012313:RNA; D004247:DNA; D015254:DNA Modification Methylases
keywords: Prokaryotic DNA methyltransferase; RNA/DNA hybrid; Relaxed specificity