BRCA1 orchestrates a novel molecular interplay at the BRCA1 and GADD153 promoters to regulate transcriptional responses to DNA damage.

DE LUCA P; VAZQUEZ E; MOIOLA C; GUERON G; ZALAZAR F; GARDNER K; DE SIERVI A

Denver, Colorado, USA

Congreso; 100th AACR Annual Meeting: American Association for Cancer Research.; 2009

The BRCA1 gene product plays numerous roles in regulating genome integrity. It interacts with crucial proteins and is considered a gene-specific transcriptional co-regulator; however, BRCA1 role in response to DNA damage is poorly understood. By chromatin immunoprecipitation and genome arrays technology (ChIP-chip) we recently determined that BRCA1 is highly enriched at the BRCA1 promoter in cancer cells. Following exposure to genotoxic agents BRCA1 is released from it own promoter in order to be recruited to other genes or sites of DNA damage, as GADD153 (growth arrest and DNA damage gene). In this study, using Tandem ChIP, we provide evidence for the first time that BRCA1 binds its own promoter trought E2F1 transcription factor demonstrating its coregulator function. Moreover, we found that the release of BRCA1 from its own promoter is accompanied by an increase in its occupancy at the GADD153 promoter and an increase in GADD153 transcription. We also determined that BRCA1 binds and regulates GADD153 promoter after DNA damage. Finnally, we established that BRCA1 directly regulates GADD153 mediated apoptosis, as we determined by Annexin V/PI in the stable transfected cells that overexpress BRCA1 or have silenced BRCA1 or GADD153 expression levels. All together these results show a new mechanism for the DNA damage response in cancer cells orchestrated by BRCA1. It suggests that BRCA1 and GADD153 show coordinate upregulation through promoter exchange of BRCA1 protein following DNA damage.