DNA H form requires a homopurine-homopyrimidine mirror repeat

• Published in: Nature (London) Vol. 330; no. 6147; p. 495
• Main Authors: Mirkin, S M, Lyamichev, V I, Drushlyak, K N, Dobrynin, V N, Filippov, S A, Frank-Kamenetskii, M D
• Format: Journal Article
• Language: English
• Published: England 03.12.1987
• Subjects: Animals; Base Sequence; DNA - metabolism; DNA, Superhelical; DNA, Viral; Endonucleases - metabolism; Humans; Hydrogen-Ion Concentration; Nucleic Acid Conformation; Oncogenic Viruses - genetics; Plasmids; Purine Nucleotides; Pyrimidine Nucleotides; Repetitive Sequences, Nucleic Acid; Single-Strand Specific DNA and RNA Endonucleases
• ISSN: 0028-0836
• DOI: 10.1038/330495a0

Regular homopurine-homopyrimidine tracts, (dG-dA)n(dT-dC)n and (dG)n(dC)n, undergo a superhelix-induced, strongly pH-dependent, structural transition into a novel DNA conformation, the H form. We have suggested that the H form can arise in any homopurine-homopyrimidine mirror repeat (H palindrome). We have now tested this prediction using a tailored series of plasmids carrying the inserts AAGGGAGAAXGGGGTATAGGGGYAAGAGGGAA, where X and Y may be either A or G, and subject them to two-dimensional gel electrophoresis. In support of our hypothesis, the inserts exhibited facile transitions into the H form for X = Y = G, or X = Y = A, whereas the transition was much more difficult or impossible for the two non-palindromes (X = A, Y = G or X = G, Y = A). We present evidence that the H form is the structural basis for S1-nuclease hypersensitivity.