Priming DNA Replication from Triple Helix Oligonucleotides : Possible Threestranded DNA in DNA Polymerases

Abstract EN

Triplex associate with a duplex DNA presenting the same polypurine or polypyrimidine-rich sequence in an antiparallel orientation.

So far, triplex forming oligonucleotides (TFOs) are known to inhibit transcription, replication, and to induce mutations.

A new property of TFO is reviewed here upon analysis of DNA breakpoint yielding DNA rearrangements; the synthesized sequence of the first direct repeat displays a skewed polypurine- rich sequence.

This synthesized sequence can bind the second homologous duplex sequence through the formation of a triple helix, which is able to prime further DNA replication.

In these case, the d(G)-rich Triple Helix Primers (THP) bind the homologous strand in a parallel manner, possibly via a RecA-like mechanism.

This novel property is shared by all tested DNA polymerases: phage, retrovirus, bacteria, and human.

These features may account for illegitimate initiation of replication upon single-strand breakage and annealing to a homologous sequence where priming may occur.

Our experiments suggest that DNA polymerases can bind three instead of two polynucleotide strands in their catalytic centre.