title: RecA protein promotes strand exchange with DNA substrates containing isoguanine and 5-methyl isocytosine.
abstract: The Escherichia coli RecA protein pairs homologous DNA molecules and promotes DNA strand exchange in vitro. We have examined DNA strand exchange between a 70 nucleotide ssDNA fragment and a 40 bp duplex, in which all G and C residues (at 18 positions distributed throughout the 40 bp exchanged region) were replaced with the nonstandard nucleosides 2'-deoxyisoguanosine (iG) and 2'-deoxy-5-methylisocytidine (MiC), respectively. We demonstrate that the nonstandard oligonucleotides are substrates for the RecA protein, permitting DNA strand exchange in vitro at a rate and efficiency comparable to exchange with normal DNA substrates. This observation provides an expanded experimental basis for discussions of potential roles for iG and MiC in a genetic code. Experiments of this type also provide another avenue for exploring RecA-facilitated DNA pairing mechanisms.
authors.affiliation: Department of Biochemistry, University of Wisconsin-Madison, 53706, USA.
authors.forename: K P
authors.initials: KP
authors.lastname: Rice
authors.forename: J C
authors.initials: JC
authors.lastname: Chaput
authors.forename: M M
authors.initials: MM
authors.lastname: Cox
authors.forename: C
authors.initials: C
authors.lastname: Switzer
mesh_terms: D044503:5-Methylcytosine / Q000031:analogs & derivatives; D003596:Cytosine / Q000031:analogs & derivatives*; D004247:DNA / Q000378:metabolism*; D004261:DNA Replication; D004277:DNA, Single-Stranded / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism*; D006147:Guanine; D008956:Models, Chemical; D008958:Models, Molecular; D009690:Nucleic Acid Conformation; D009838:Oligodeoxyribonucleotides; D011938:Rec A Recombinases / Q000378:metabolism*; D011995:Recombination, Genetic; D013379:Substrate Specificity; D013816:Thermodynamics
chemical_list: C412877:5-methyl isocytosine; D004277:DNA, Single-Stranded; D004268:DNA-Binding Proteins; D009838:Oligodeoxyribonucleotides; D006147:Guanine; D044503:5-Methylcytosine; D003596:Cytosine; D004247:DNA; C008183:isoguanine; D011938:Rec A Recombinases