Mechanism of RNA polymerase II stalling by DNA alkylation

Area of Science:

• Molecular Biology
• Biochemistry
• Cancer Research

Background:

• Anticancer agents forming DNA adducts in the minor groove can inhibit DNA replication and transcription, inducing apoptosis.
• Therapeutic resistance often arises from cellular proficiency in removing drug-induced DNA damage.
• Acylfulvenes are experimental anticancer agents with a unique repair profile, potentially stalling RNA Polymerase II (Pol II) and triggering transcription-coupled nucleotide excision repair.

Purpose of the Study:

• To elucidate how DNA alkylation impairs transcription by RNA Pol II.
• To understand the mechanism of RNA Pol II stalling caused by minor-groove DNA alkylation.
• To investigate the role of acylfulvene analogs in DNA damage and polymerase activity.

Main Methods:

• Incorporation of acylfulvene analogs (3-deaza-3-methoxynaphtylethyl-adenosine and smaller analogs) into DNA oligonucleotides.
• In vitro assessment of RNA Pol II transcription elongation using modified DNA oligonucleotides.
• Crystal structure analysis of RNA Pol II interacting with DNA containing acylfulvene adducts.

Main Results:

• RNA Pol II was strongly blocked by the 3-deaza-3-methoxynaphtylethyl-adenosine analog, while smaller analogs were bypassed.
• Crystal structure revealed that the 3-deaza-3-methoxynaphtylethyl-adenosine adduct can occupy the +1 templating position.
• The adduct impairs the closing of the Pol II trigger loop and subsequent polymerase translocation.

Conclusions:

• Minor-groove DNA alkylation by acylfulvene analogs impairs RNA Pol II transcription.
• A specific mechanism of RNA Pol II stalling involves adducts occupying the active site and hindering polymerase movement.
• This study provides insights into how RNA Pol II interacts with minor-groove DNA damage, establishing a mechanism for drug resistance.