title: Antiparallel, intramolecular triplex DNA stimulates homologous recombination in human cells.
abstract: The DNA motif 5'-AAGGGAGAAXGGGTATAGGGYAAGAGGGAA-3' (named XY32) is an H-palindrome and has been shown to undergo a superhelix-induced, pH-dependent structural transition to H-form (pyrimidine purineo pyrimidine triplex) DNA when X = Y = A (AA32) or X = Y = G (GG32), but when X = A and Y = G (AG32) or X = G and Y = A (GA32), the transition is much more difficult [Mirkin, S. (1987) Nature (London) 330, 495-497]. Furthermore, AA32, GG32, and GA32 triplexes have the proper sequence structure to potentially form pyrimidineopurineopurine (*H-form) triplexes, but AG32 does not [Beal, P. A. & Dervan, P. B. (1992) Nucleic Acids Res. 20, 2773-2776]. Using an in vivo plasmid-plasmid recombination assay system in cultured human cells, we have found that AA32, GA32, and GG32 stimulate homologous recombination between plasmids 3- to 5-fold when both recombination substrates contain these triplex-forming sequences, whereas AG32, which differs from the others by only 1 or 2 bp, does not significantly affect the frequency of recombination. Double-strand breaks, which destroy supercoiling, nullify the stimulation. Therefore, stimulation of homologous recombination between plasmids containing these sequences correlates with their triplex-forming potential. Crosses in which the triplex-forming sequence is inserted into only one substrate exhibit an intermediate stimulation, suggesting that the inserts are acting alone as intramolecular triplexes.
authors.affiliation: Department of Genetics, University of Illinois, Chicago 60612.
authors.forename: S M
authors.initials: SM
authors.lastname: Rooney
authors.forename: P D
authors.initials: PD
authors.lastname: Moore
mesh_terms: D001483:Base Sequence; D002460:Cell Line; D004247:DNA / Q000378:metabolism*; D005822:Genetic Vectors; D006801:Humans; D019868:Kanamycin Kinase; D008961:Models, Structural; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000096:biosynthesis; D010957:Plasmids; D011995:Recombination, Genetic; D015183:Restriction Mapping; D014407:Tumor Cells, Cultured; D001749:Urinary Bladder Neoplasms
chemical_list: C051802:triplex DNA; D004247:DNA; D017853:Phosphotransferases (Alcohol Group Acceptor); D019868:Kanamycin Kinase