The EMSY threonine 207 phospho-site is required for EMSY-driven suppression of DNA damage repair

Abstract

BRCA1 and BRCA2 are essential for the repair of double-strand DNA breaks, and alterations in these genes are a hallmark of breast and ovarian carcinomas. Other functionally related genes may also play important roles in carcinogenesis. Amplification of EMSY, a putative BRCAness gene, has been suggested to impair DNA damage repair by suppressing BRCA2 function. We employed direct repeat GFP (DR-GFP) and RAD51 foci formation assays to show that EMSY overexpression impairs the repair of damaged DNA, suggesting that EMSY belongs to the family of BRCAness proteins. We also identified a novel phospho-site at threonine 207 (T207) and demonstrated its role in EMSY-driven suppression of DNA damage repair. In vitro kinase assays established that protein kinase A (PKA) directly phosphorylates the T207 phospho-site. Immunoprecipitation experiments suggest that EMSY-driven suppression of DNA damage repair is a BRCA2-independent process. The data also suggest that EMSY amplification is a BRCAness feature, and may help to expand the population of patients who could benefit from targeted therapies that are also effective in BRCA1/2-mutant cancers.

New Insights into Protein Kinase B/Akt Signaling: Role of Localized Akt Activation and Compartment-Specific Target Proteins for the Cellular Radiation Response

“…Instead, overexpression of Akt3 in a genetic model of PDGF-driven murine glioma [ 8 ] or of the clinically relevant activating mutation Akt1-E17K in murine prostate cancer cells facilitated the repair of radiation-induced DNA damage, thereby increasing radiation resistance [ 23 ]. But, Akt can also exert inhibitory actions on the proper repair of DNA damage [ 243 , 141 , 249 ]. In the following paragraphs we highlight current knowledge about important nuclear proteins with suspected regulation by Akt and their positive or negative effect on DNA DSB repair ( Figure 3 ).…”

“…Interestingly, EMSY constitutes another Akt substrate with potential impact on DNA repair if overexpressed [ 249 ]. Breast cancer and ovarian cancer cells show strong amplification of EMSY and this is associated with poor prognosis [ 258 ].…”

“…Breast cancer and ovarian cancer cells show strong amplification of EMSY and this is associated with poor prognosis [ 258 ]. EMSY can bind to BRCA2, a protein implicated in transcriptional regulation and DNA repair, leading to deactivation and transcriptional repression of BRCA2 [ 144 , 145 , 249 , 259 ]. While overexpression of EMSY repressed interferon-stimulated genes in breast and ovarian cancer cells in a BRCA2-dependent manner, its knockdown had opposite effects [ 144 , 145 ].…”

Clinical importance of the EMSY gene expression and polymorphisms in ovarian cancer

“…It co-localizes with γH2AX foci, a marker of double-strand breaks, after ionizing irradiation. Overexpression of EMSY elicits a “chromosome instability phenotype” similar to that observed in BRCA2-deficient cells [ 7 , 11 , 41 ]. Consistently, amplification of the EMSY gene has been proposed to mimic the BRCA2 -mutant phenotype which might be a mechanism of BRCA2 pathway inactivation and consequent sensitization of cancer cells to DNA damaging drugs.…”

“…Moreover, siRNA-mediated silencing of EMSY expression in cell lines with EMSY amplification had no effect on their sensitivity to cisplatin and olaparib. Noteworthy, there is also one recent study that suggested that EMSY participation in DNA repair might be BRCA2-independent [ 41 ]. Considering all these discrepancies, the role of EMSY in DNA repair and cancer therapy still remains unclear and requires further investigation.…”