Benzo[a]pyrene represses DNA repair through altered E2F1/E2F4 function marking an early event in DNA damage-induced...

Area of Science:

• Molecular Biology
• Genetics
• Cell Biology

Background:

• Transcriptional regulation of DNA repair is crucial for maintaining genomic integrity under genotoxic stress.
• Environmental carcinogens can disrupt normal cellular processes, including DNA repair mechanisms.

Purpose of the Study:

• To investigate the effect of benzo[a]pyrene (B[a]P) on DNA repair gene expression.
• To elucidate the molecular mechanisms underlying B[a]P-induced DNA repair downregulation.
• To determine if this repression is linked to cellular senescence.

Main Methods:

• Analysis of mismatch repair (MMR) and homologous recombination (HR) gene expression.
• Investigation of E2F1 signaling pathways and the p21-dependent E2F4/DREAM complex.
• Cell cycle analysis and assessment of senescence markers following B[a]P exposure.

Main Results:

• B[a]P treatment leads to transcriptional repression of MMR genes (MSH2, MSH6, EXO1) and RAD51.
• E2F1 signaling is abrogated via proteasomal degradation (G2) or mRNA downregulation (G1), mediated by the p21-dependent E2F4/DREAM complex.
• Repression of DNA repair is observed with B[a]P metabolites and ionizing radiation, coinciding with p53/p21-triggered senescence.

Conclusions:

• Downregulation of MMR and HR is an early event in genotoxic stress-induced senescence.
• Persistent suppression of DNA repair may contribute to maintaining the senescence phenotype.
• Accumulation of unrepaired DNA lesions could be a consequence of this repair deficiency in senescent cells.