DNA damage by nitrogen mustard in a gene containing multiple Sp1-binding sites

Area of Science:

• Molecular Biology
• Genetics
• Toxicology

Background:

• The human cytochrome c(1) gene promoter is TATA-less and relies on Sp1-binding elements for transcriptional regulation.
• Nitrogen mustards are alkylating agents used in chemotherapy, but their precise molecular mechanisms of toxicity are not fully elucidated.

Purpose of the Study:

• To investigate whether nitrogen mustard induces DNA damage at Sp1-binding sites within the cytochrome c(1) gene promoter.
• To determine if this damage affects Sp1 binding and subsequent gene transcription.

Main Methods:

• Quantitative PCR to detect and quantify DNA lesions in the Sp1-binding region of the cytochrome c(1) gene in HeLa cells.
• Sp1 competition assay to assess the impact of nitrogen mustard exposure on Sp1 protein binding to the promoter.

Main Results:

• Nitrogen mustard exposure induced DNA lesions in the Sp1-binding region of the cytochrome c(1) gene in HeLa cells.
• Lesion formation increased with exposure time, with significant alkylation occurring within 1 hour.
• Nitrogen mustard inhibited the binding of Sp1 transcription factor to the target DNA sequence.

Conclusions:

• Nitrogen mustard directly damages Sp1-binding sites in the cytochrome c(1) gene promoter.
• This damage interferes with Sp1-mediated transcriptional activation.
• Interference with gene activation at Sp1-binding sites likely contributes to the overall toxicity of nitrogen mustard.