Triple-helix specific ligands stabilize H-DNA conformation

Area of Science:

• Molecular Biology
• Genetics
• Drug Discovery

Background:

• Oligopurine-oligopyrimidine mirror-repeat sequences can form H-DNA under superhelical stress.
• The antitumor drug benzo[e]pyridoindole (BePI) binds triplex DNA more strongly than duplex DNA.
• BePI previously stabilized intermolecular triple helices at specific DNA sequences.

Purpose of the Study:

• To investigate BePI's effect on intramolecular triple helices.
• To determine if H-DNA structures stabilized by BePI can inhibit DNA polymerases and gene transcription.
• To explore BePI as a potential therapeutic agent targeting H-DNA.

Main Methods:

• Studied BePI's stabilization of intramolecular H-DNA.
• Assessed inhibition of DNA polymerases (T7, E. coli, Taq) in vitro using H-DNA and BePI.
• Investigated inhibition of beta-lactamase gene transcription in vivo using a modified E. coli system.
• Utilized chemical probes (chloroacetaldehyde) to confirm H-DNA stabilization.

Main Results:

• BePI strongly stabilizes intramolecular triple helices.
• H-DNA structures in the presence of BePI irreversibly inhibited DNA polymerase elongation in vitro.
• A specific DNA sequence insertion inhibited beta-lactamase gene transcription in vivo.
• BePI stabilized supercoiling-induced H-DNA structures.

Conclusions:

• BePI stabilizes both intermolecular and intramolecular H-DNA structures.
• H-DNA formation, stabilized by BePI, can inhibit essential DNA processes like replication and transcription.
• This study introduces a new class of genetic structures (H-DNA) as targets for antitumor agents.