title: Replication, transcription and nuclease digestion of the unusual X-DNA double helix of poly(amino2dA-dT).
abstract: The alternating copolymer poly(amino2dA-dT) isomerizes into the unusual X-DNA double helix at low-salt aqueous conditions (Vorlicková et al., J. Biomolec. Struct. Dyn. 6, 503-510 (1988)). This observation allowed us to start studies on how the X-DNA is recognized, copied and hydrolyzed by various enzymes. In the present paper X-DNA replication, transcription and digestion by various polymerases and nucleases, respectively, are examined and compared to appropriate controls. It is found that X-DNA is a poor primer-template for DNA synthesis by the E. coli Klenow DNA polymerase (12% of the activity observed with B-DNA), the Micrococcus luteus DNA polymerase I (25%) and the AMV reverse transcriptase (51%). In contrast, X-DNA is a better template by 74% than B-DNA for calf thymus DNA polymerase alpha. For transcription by E. coli RNA polymerase enzyme poly(amino2dA-dT) did not serve as a template at all in either B or X conformation. Poly(amino2dA-dT) in its B form proved to be much more stable than poly(dA-dT) against hydrolysis by pancreatic DNase and snake venom phosphodiesterase. Formation of the X conformation in poly(amino2dA-dT) decreased this large difference in nuclease stability.
authors.affiliation: Central Research Institute for Chemistry, Hungarian Academy of Sciences, Budapest.
authors.forename: J
authors.initials: J
authors.lastname: Sági
authors.forename: K
authors.initials: K
authors.lastname: Ebinger
authors.forename: M
authors.initials: M
authors.lastname: Vorlicková
authors.forename: J
authors.initials: J
authors.lastname: Kypr
authors.forename: L
authors.initials: L
authors.lastname: Otvös
mesh_terms: D004261:DNA Replication; D004259:DNA-Directed DNA Polymerase / Q000378:metabolism; D012321:DNA-Directed RNA Polymerases / Q000378:metabolism; D003851:Deoxyribonucleases / Q000378:metabolism; D009690:Nucleic Acid Conformation; D011089:Polydeoxyribonucleotides / Q000378:metabolism*; D014158:Transcription, Genetic
chemical_list: D011089:Polydeoxyribonucleotides; C054693:poly(amino(2)dA-dT); D012321:DNA-Directed RNA Polymerases; D004259:DNA-Directed DNA Polymerase; D003851:Deoxyribonucleases