Suicidal nucleotide sequences for DNA polymerization.
Studying the activity of T7 DNA polymerase (Sequenase) on open circular DNAs, we observed virtually complete termination within potential triplex-forming sequences. Mutations destroying the triplex potential of the sequences prevented termination, while compensatory mutations restoring triplex potential restored it. We hypothesize that strand displacement during DNA polymerization of double-helical templates brings three DNA strands (duplex DNA downstream of the polymerase plus a displaced overhang) into close proximity, provoking triplex formation, which in turn prevents further DNA synthesis. Supporting this idea, we found that Sequenase is unable to propagate through short triple-helical stretches within single-stranded DNA templates. Thus, DNA polymerase, by inducing triplex formation at specific sequences in front of the replication fork, causes self-termination. Possible biological implications of such 'conformational suicide' are discussed. Our data also provide a novel way to target DNA polymerases at specific sequences using triplex-forming oligonucleotides.
Samadashwily
G M
GM
Department of Genetics, University of Illinois at Chicago 60612.
Dayn
A
A
Mirkin
S M
SM
D001483:Base Sequence; D004247:DNA / Q000096:biosynthesis*; D004277:DNA, Single-Stranded / Q000378:metabolism; D004259:DNA-Directed DNA Polymerase / Q000378:metabolism*; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D013329:Structure-Activity Relationship; D013379:Substrate Specificity; D013698:Templates, Genetic
D004277:DNA, Single-Stranded; D004247:DNA; C034970:bacteriophage T7 induced DNA polymerase; D004259:DNA-Directed DNA Polymerase