Replication, transcription and nuclease digestion of the unusual X-DNA double helix of poly(amino2dA-dT)

• Published in: Journal of biomolecular structure & dynamics Vol. 7; no. 5; p. 1073
• Main Authors: Sági, J, Ebinger, K, Vorlicková, M, Kypr, J, Otvös, L
• Format: Journal Article
• Language: English
• Published: England 01.04.1990
• Subjects: Deoxyribonucleases - metabolism; DNA Replication; DNA-Directed DNA Polymerase - metabolism; DNA-Directed RNA Polymerases - metabolism; Nucleic Acid Conformation; Polydeoxyribonucleotides - metabolism; Transcription, Genetic
• ISSN: 0739-1102
• DOI: 10.1080/07391102.1990.10508547

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.