title: A hexanucleotide sequence (dC1-dC6 tract) restricts the dC-specific cleavage of single-stranded DNA by endonuclease IV of bacteriophage T4.
abstract: Endonuclease (Endo) IV encoded by denB of bacteriophage T4 is an enzyme that cleaves single-stranded (ss) DNA in a dC-specific manner. Previously we have demonstrated that a dTdCdA is most preferable for Endo IV when an oligonucleotide substrate having a single dC residue is used. Here we demonstrate that Endo IV cleaves ssDNAs exclusively at the 5'-proximal dC where a sequence comprises dC residues both at the 5' proximal and 3' proximal positions (a dCs tract-dependent cleavage). The dCs tract-dependent cleavage is efficient and occurs when a dCs tract has at least 6 bases. Some dCs tracts larger than 6 bases behave as that of 6 bases (an extended dCs tract), while some others do not. One decameric dCs tract was shown to be cleavable in a dCs tract-dependent manner, but that with 13 dCs was not. The dCs tract-dependent cleavage is enhanced by the presence of a third dC residue at least for a 6 or 7 dCs tract. In contrast to the dCs tract-dependent cleavage, a dCs tract-independent one is generally inefficient and if two modes are possible for a substrate DNA, a dCs tract-dependent mode prevails. A model for the dCs tract-dependent cleavage is proposed.
authors.affiliation: Department of Applied Biological Science, Nihon University College of Bioresource Sciences, Fujisawa-shi, Kanagawa 252-8510, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Ohshima
authors.forename: Nobutaka
authors.initials: N
authors.lastname: Hirano
authors.forename: Hideo
authors.initials: H
authors.lastname: Takahashi
mesh_terms: D017122:Bacteriophage T4 / Q000201:enzymology*; D004277:DNA, Single-Stranded / Q000737:chemistry* / Q000378:metabolism; D004279:DNA, Viral / Q000737:chemistry / Q000378:metabolism; D043223:Deoxyribonuclease IV (Phage T4-Induced) / Q000378:metabolism*; D007700:Kinetics; D011066:Poly C / Q000737:chemistry*; D013379:Substrate Specificity
chemical_list: D004277:DNA, Single-Stranded; D004279:DNA, Viral; C023826:poly(dC); D011066:Poly C; D043223:Deoxyribonuclease IV (Phage T4-Induced)