Genome-wide mapping of estrogen receptor-beta-binding regions reveals extensive cross-talk with transcription factor...

Area of Science:

• Molecular Biology
• Genomics
• Cancer Research

Background:

• Estrogen signaling pathways are critical in cellular processes and cancer.
• Nonclassical estrogen receptor (ER) signaling involves interactions with other transcription factors, but mechanisms remain unclear.
• Previous in vitro studies on ER and activator protein-1 (AP-1) interactions yielded conflicting results.

Purpose of the Study:

• To elucidate the genomic binding sites of ERbeta and its functional association with AP-1 in breast cancer cells.
• To understand the mechanistic basis of nonclassical estrogen signaling.
• To investigate the role of AP-1 in mediating ERbeta recruitment and estrogen signaling.

Main Methods:

• Genome-wide identification of ERbeta binding sites using ChIP-on-chip in MCF7 breast cancer cells.
• Chromatin immunoprecipitation (ChIP) and re-ChIP assays to confirm ERbeta and AP-1 co-occupancy on DNA.
• Short interfering RNA (siRNA) to knock down c-Fos and c-Jun expression.

Main Results:

• Identified 1,457 high-confidence ERbeta binding sites.
• Approximately 60% of ERbeta-bound regions contained AP-1-like binding sites and estrogen response element-like sites.
• Confirmed physical association and co-occupancy of ERbeta and AP-1 on chromatin.
• Knockdown of c-Fos or c-Jun reduced ERbeta recruitment, indicating AP-1's role in ERbeta binding.
• ERalpha and ERbeta recruitment varied depending on the gene and response to antiestrogens.

Conclusions:

• Estrogen receptor beta (ERbeta) directly binds to genomic regions associated with the activator protein-1 (AP-1) transcription factor.
• AP-1 plays a critical role in mediating ERbeta recruitment to chromatin, influencing estrogen signaling in breast cancer.
• These findings reveal a novel crosstalk between ERbeta and AP-1 at the genomic level, impacting breast cancer cell regulation.