Consequences of cisplatin binding on nucleosome structure and dynamics

Area of Science:

• Molecular Biology
• Structural Biology
• Biochemistry

Background:

• Cisplatin is a widely used platinum-based chemotherapy drug.
• Understanding cisplatin's interaction with DNA at the nucleosome level is crucial for cancer therapy.
• The eukaryotic nuclear environment, including nucleosomes, influences DNA-drug interactions.

Purpose of the Study:

• To investigate the structural and functional consequences of cisplatin binding to DNA within a nucleosome.
• To elucidate how cisplatin-induced DNA adducts affect nucleosome positioning and dynamics.
• To determine the impact of cisplatin-damaged nucleosomal DNA on transcription by RNA polymerase.

Main Methods:

• X-ray crystallography to determine the structure of a platinated nucleosome.
• In vitro nucleosome mobility assays to assess DNA sliding.
• In vitro transcription assays to evaluate RNA polymerase progression on damaged DNA templates.

Main Results:

• The crystal structure revealed how cisplatin adducts dictate DNA rotational positioning within the nucleosome.
• A single platinum adduct was found to inhibit ATP-independent DNA sliding around the histone octamer.
• RNA polymerases could transcribe cisplatin-damaged nucleosomal DNA but stalled upon encountering the cross-link on the template strand.

Conclusions:

• Cisplatin binding to DNA significantly alters nucleosome structure and dynamics.
• Platinum-induced DNA adducts pose a barrier to DNA repair and transcription processes.
• These findings enhance the understanding of platinum anticancer drug mechanisms and transcription inhibition.