DNA Damage-Binding Complex Recruits HDAC1 to Repress Bcl-2 Transcription in Human Ovarian Cancer Cells

Abstract

Elevated expression of the anti-apoptotic factor Bcl-2 is believed to be one of the contributing factors to an increased relapse rate associated with multiple cisplatin-resistant cancers. DNA damage-binding protein complex subunit 2 (DDB2) has recently been revealed to play an important role in sensitizing human ovarian cancer cells to cisplatin-induced apoptosis through the down-regulation of Bcl-2, but the underlying molecular mechanism remains poorly defined. Here, we report that DDB2 functions as a transcriptional repressor for Bcl-2 in combination with DDB1. Quantitative ChIP and EMSA analysis revealed that DDB2 binds to a specific cis-acting element at the 5′-end of bcl-2 P1 promoter. Overexpression of DDB2 resulted in marked losses of histone H3K9,14 acetylation along the bcl-2 promoter and enhancer regions, concomitant with a local enrichment of HDAC1 to the bcl-2 P1 core promoter in ovarian cancer cells. Co-immunoprecipitation analysis and in vitro binding assay identified a physical interaction between DDB1 and HDAC1, while downregulation of HDAC1 significantly enhanced bcl-2 promoter activity. Finally, in comparison to wild-type DDB2, mutated DDB2, which is unable to repress Bcl-2 transcription, mediates a compromised apoptosis upon cisplatin treatment. Taken together, our data support a model wherein DDB1 and DDB2 cooperate with each other to repress bcl-2 transcription. DDB2 recognizes and binds to the bcl-2 P1 promoter, and HDAC1 is recruited through the DDB1 subunit associated with DDB2, to deacetylate histone H3K9,14 across bcl-2 regulatory regions, resulting in suppressed bcl-2 transcription. Thus, increasing the expression of DDB complex may provide a molecular strategy for cancer therapy.

Damaged DNA-binding protein down-regulates epigenetic mark H3K56Ac through histone deacetylase 1 and 2

“…3A). These results confirmed our previous observations and indicated that DDB2 physically interacts with HDAC1 [38]. We further investigated whether DDB2 affects translocation of HDAC1 to chromatin.…”

DDB2 Suppresses Tumorigenicity by Limiting the Cancer Stem Cell Population in Ovarian Cancer

“…DDB2 expression lentiviruses were generated as described before (21). To establish shDDB2 stably transfected cell lines, MISSION shDDB2 (TRCN0000083993) plasmids (Sigma) were transfected into 2008 cells using eletroporation.…”

“…The low expression of DDB2 in cisplatin-resistant ovarian cancer cell lines (18) and high-grade colon cancer (19) and skin cancer (20) indicates a link between DDB2 expression and tumor progression. Recently, new functions of DDB2 beyond its role in DNA repair have been identified, e.g., inhibiting cellular apoptosis through downregulation of Bcl-2 (18, 21) and p21 (22), suppressing colon tumor metastasis through blocking epithelial–mesenchymal transition (EMT; ref. 19), and limiting the motility and invasiveness of invasive human breast tumor cells by regulating NF-κB activity (23), as well as mediating premature senescence (24).…”

DDB2 increases radioresistance of NSCLC cells by enhancing DNA damage responses

“…Our previous studies have revealed the role of DDB2 in mediating the sensitivity of ovarian cancer cells to cisplatin [12, 13]. As a DNA damage binding protein, DDB2 is involved in the repair of UV-induced CPD by the NER pathway, but is not required for the repair of cisplatin-induced intrastrand crosslinks.…”