title: Duality of polynucleotide substrates for Phi29 DNA polymerase: 3'-->5' RNase activity of the enzyme.
abstract: Phi29 DNA polymerase is a small DNA-dependent DNA polymerase that belongs to eukaryotic B-type DNA polymerases. Despite the small size, the polymerase is a multifunctional proofreading-proficient enzyme. It catalyzes two synthetic reactions (polymerization and deoxynucleotidylation of Phi29 terminal protein) and possesses two degradative activities (pyrophosphorolytic and 3'-->5' DNA exonucleolytic activities). Here we report that Phi29 DNA polymerase exonucleolyticaly degrades ssRNA. The RNase activity acts in a 3' to 5' polarity. Alanine replacements in conserved exonucleolytic site (D12A/D66A) inactivated RNase activity of the enzyme, suggesting that a single active site is responsible for cleavage of both substrates: DNA and RNA. However, the efficiency of RNA hydrolysis is approximately 10-fold lower than for DNA. Phi29 DNA polymerase is widely used in rolling circle amplification (RCA) experiments. We demonstrate that exoribonuclease activity of the enzyme can be used for the target RNA conversion into a primer for RCA, thus expanding application potential of this multifunctional enzyme and opening new opportunities for RNA detection.
authors.affiliation: Fermentas UAB, Graiciuno 8, Vilnius LT-02241, Lithuania. laguna@fermentas.lt
authors.forename: Arunas
authors.initials: A
authors.lastname: Lagunavicius
authors.forename: Zivile
authors.initials: Z
authors.lastname: Kiveryte
authors.forename: Vilma
authors.initials: V
authors.lastname: Zimbaite-Ruskuliene
authors.forename: Tomas
authors.initials: T
authors.lastname: Radzvilavicius
authors.forename: Arvydas
authors.initials: A
authors.lastname: Janulaitis
mesh_terms: D000595:Amino Acid Sequence; D017103:Bacillus Phages / Q000201:enzymology* / Q000235:genetics; D001483:Base Sequence; D020134:Catalytic Domain; D004270:DNA, Circular / Q000378:metabolism; D004259:DNA-Directed DNA Polymerase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006868:Hydrolysis; D008958:Models, Molecular; D008969:Molecular Sequence Data; D012313:RNA / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity
chemical_list: D004270:DNA, Circular; D012333:RNA, Messenger; D012313:RNA; D004259:DNA-Directed DNA Polymerase