RESUMO
Efficient DNA repair and limitation of genome rearrangements rely on crosstalk between different DNA double-strand break (DSB) repair pathways, and their synchronization with the cell cycle. The selection, timing and efficacy of DSB repair pathways are influenced by post-translational modifications of histones and DNA damage repair (DDR) proteins, such as phosphorylation. While the importance of kinases and serine/threonine phosphatases in DDR have been extensively studied, the role of tyrosine phosphatases in DNA repair remains poorly understood. In this study, we have identified EYA4 as the protein phosphatase that dephosphorylates RAD51 on residue Tyr315. Through its Tyr phosphatase activity, EYA4 regulates RAD51 localization, presynaptic filament formation, foci formation, and activity. Thus, it is essential for homologous recombination (HR) at DSBs. DNA binding stimulates EYA4 phosphatase activity. Depletion of EYA4 decreases single-stranded DNA accumulation following DNA damage and impairs HR, while overexpression of EYA4 in cells promotes dephosphorylation and stabilization of RAD51, and thereby nucleoprotein filament formation. Our data have implications for a pathological version of RAD51 in EYA4-overexpressing cancers.
Assuntos
Rad51 Recombinase , Transativadores , DNA , Reparo do DNA , Proteínas de Ligação a DNA/genética , Proteínas de Ligação a DNA/metabolismo , Recombinação Homóloga/genética , Fosfoproteínas Fosfatases/metabolismo , Rad51 Recombinase/genética , Rad51 Recombinase/metabolismo , Tirosina/genética , Humanos , Transativadores/metabolismoRESUMO
The Eyes Absent (EYA) family of proteins is an atypical group of four dual-functioning protein phosphatases (PP), which have been linked to many vital cellular processes and organogenesis pathways. The four family members of this PP family possess transcriptional activation and phosphatase functions, with serine/threonine and tyrosine phosphatase domains. EYA4 has been associated with several human cancers, with tumor-suppressing and tumor-promoting roles. However, EYA4 is the least well-characterized member of this unique family of PP, with its biological functions and molecular mechanisms in cancer progression, particularly in breast cancer, still largely unknown. In the present study, we found that the over-expression of EYA4 in breast tissue leads to an aggressive and invasive breast cancer phenotype, while the inhibition of EYA4 reduced tumorigenic properties of breast cancer cells in vitro and in vivo. Cellular changes downstream of EYA4, including cell proliferation and migration, may explain the increased metastatic power of breast cancer cells over-expressing EYA4. Mechanistically, EYA4 prevents genome instability by inhibiting the accumulation of replication-associated DNA damage. Its depletion results in polyploidy as a consequence of endoreplication, a phenomenon that can occur in response to stress. The absence of EYA4 leads to spontaneous replication stress characterized by the activation of the ATR pathway, sensitivity to hydroxyurea, and accumulation of endogenous DNA damage as indicated by increased γH2AX levels. In addition, we show that EYA4, specifically its serine/threonine phosphatase domain, plays an important and so far, unexpected role in replication fork progression. This phosphatase activity is essential for breast cancer progression and metastasis. Taken together, our data indicate that EYA4 is a novel potential breast cancer oncogene that supports primary tumor growth and metastasis. Developing therapeutics aimed at the serine/threonine phosphatase activity of EYA4 represents a robust strategy for killing breast cancer cells, to limit metastasis and overcome chemotherapy resistance caused by endoreplication and genomic rearrangements.
Assuntos
Neoplasias da Mama , Humanos , Feminino , Neoplasias da Mama/genética , Transativadores/genética , Transativadores/metabolismo , Linhagem Celular Tumoral , Proteínas Tirosina Fosfatases/genética , Proteínas Tirosina Fosfatases/metabolismo , Fosfoproteínas Fosfatases/genética , SerinaRESUMO
The Eyes Absent (EYA) family of proteins is an atypical group of four dual-functioning protein phosphatases, which have been linked to many vital cellular processes and organogenesis pathways. Like the other isoforms, EYA4 possesses transcriptional activation and phosphatase functions, with serine/threonine and tyrosine phosphatase domains. EYA4 has been associated with several human cancers, with tumor-suppressing and tumor-promoting roles. However, EYA4 is the least well-characterized member of this unique family of phosphatases, with its biological functions and molecular mechanisms in cancer progression, particularly in breast cancer, still largely unknown. In the present study, we found that the over-expression of EYA4 in breast tissue leads to an aggressive and invasive breast cancer phenotype, while the inhibition of EYA4 reduced tumorigenic properties of breast cancer cells in vitro and in vivo . Cellular changes downstream of EYA4, including cell proliferation and migration, may explain the increased metastatic power of breast cancer cells over-expressing EYA4. Mechanistically, EYA4 prevents genome instability by inhibiting the accumulation of replication-associated DNA damage. Its depletion results in polyploidy as a consequence of endoreplication, a phenomenon that can occur in response to stress. The absence of EYA4 leads to spontaneous replication stress characterized by the activation of the ATR pathway, sensitivity to hydroxyurea, and accumulation of endogenous DNA damage as indicated by increased γH2AX levels. In addition, we show that EYA4, specifically its serine/threonine phosphatase domain, plays an important and so far, unexpected role in replication fork progression. This phosphatase activity is essential for breast cancer progression and metastasis. Taken together, our data indicate that EYA4 is a novel breast cancer oncogene that supports primary tumor growth and metastasis. Developing therapeutics aimed at the serine/threonine phosphatase activity of EYA4 represents a robust strategy for killing breast cancer cells, to limit metastasis and overcome chemotherapy resistance caused by endoreplication and genomic rearrangements.
RESUMO
PURPOSE: Chromatin remodeling plays an essential role in regulating transcriptional networks and timing of gene expression. Chromatin remodelers such as SWItch/Sucrose Non-Fermentable (SWI/SNF) harbor many protein components, with the catalytic subunit providing ATPase activity to displace histones along or from the DNA molecules, and associated subunits ensuring tissue specificity and transcriptional or co-transcriptional activities. Mutations in several of the SWI/SNF subunits have been linked to cancer. Here, we investigate between SMARCD3/Baf60c expression and hormone-positive (ER+) breast cancer. METHODS: The level of SMARCD3 was detected by immunohistochemistry in breast cancer patient samples, and expression levels of SMARCD1, SMARCD2, and SMARCD3 were investigated using publicly available datasets from large cohorts of breast cancer patients. Using molecular biology and microscopy, we interrogated the cellular consequences of lower SMARCD3 expression. RESULTS: Lower proliferation rates were observed in SMARCD3-depleted cells, which reflects a failure of the cell cycle progression and an increase in endoreplication. In the absence of SMARCD3, p21 accumulates in cells, but does not halt the cell cycle, and DNA damage accumulates and remains unrepaired. CONCLUSION: Taken together, our data begin to explain why ER+ breast cancer patients with low-SMARCD3 expressing tumors exhibit reduced survival rates compared to patients expressing normal or higher levels of SMARCD3. SMARCD3 might act as a tumor suppressor through regulation of cell cycle checkpoints and could be a reliable and specific breast cancer prognostic biomarker.
Assuntos
Neoplasias da Mama , Fatores de Transcrição , Neoplasias da Mama/genética , Ciclo Celular/genética , Dano ao DNA , Feminino , Humanos , Sacarose , Fatores de Transcrição/genéticaRESUMO
Breast cancer risk is strongly associated with an intergenic region on 11q13. We have previously shown that the strongest risk-associated SNPs fall within a distal enhancer that regulates CCND1. Here, we report that, in addition to regulating CCND1, this enhancer regulates two estrogen-regulated long noncoding RNAs, CUPID1 and CUPID2. We provide evidence that the risk-associated SNPs are associated with reduced chromatin looping between the enhancer and the CUPID1 and CUPID2 bidirectional promoter. We further show that CUPID1 and CUPID2 are predominantly expressed in hormone-receptor-positive breast tumors and play a role in modulating pathway choice for the repair of double-strand breaks. These data reveal a mechanism for the involvement of this region in breast cancer.
Assuntos
Neoplasias da Mama/genética , Cromossomos Humanos Par 11/genética , Ciclina D1/genética , Reparo do DNA/genética , RNA Longo não Codificante/genética , Linhagem Celular Tumoral , Cromatina/metabolismo , Quebras de DNA de Cadeia Dupla , Dano ao DNA/genética , Elementos Facilitadores Genéticos/genética , Estrogênios/metabolismo , Feminino , Regulação Neoplásica da Expressão Gênica , Predisposição Genética para Doença/genética , Humanos , Células MCF-7 , Polimorfismo de Nucleotídeo Único/genética , Regiões Promotoras Genéticas/genética , Interferência de RNA , RNA Guia de Cinetoplastídeos/genética , RNA Interferente Pequeno/genéticaRESUMO
Exposure of melanocytes to ultraviolet radiation (UVR) induces the formation of UV lesions that can produce deleterious effects in genomic DNA. Encounters of replication forks with unrepaired UV lesions can lead to several complex phenomena, such as the formation of DNA double-strand breaks (DSBs). The NR4A family of nuclear receptors are transcription factors that have been associated with mediating DNA repair functions downstream of the MC1R signaling pathway in melanocytes. In particular, emerging evidence shows that upon DNA damage, the NR4A2 receptor can translocate to sites of UV lesion by mechanisms requiring post-translational modifications within the N-terminal domain and at a serine residue in the DNA-binding domain at position 337. Following this, NR4A2 aids in DNA repair by facilitating chromatin relaxation, allowing accessibility for DNA repair machinery. Using A2058 and HT144 melanoma cells engineered to stably express wild-type or mutant forms of the NR4A2 proteins, we reveal that the expression of functional NR4A2 is associated with elevated cytoprotection against UVR. Conversely, knockdown of NR4A2 expression by siRNA results in a significant loss of cell viability after UV insult. By analyzing the kinetics of the ensuing 53BP1 and RAD51 foci following UV irradiation, we also reveal that the expression of mutant NR4A2 isoforms, lacking the ability to translocate, transactivate, or undergo phosphorylation, display compromised repair capacity.Implications: These data expand the understanding of the mechanism by which the NR4A2 nuclear receptor can facilitate DNA DSB repair. Mol Cancer Res; 15(9); 1184-96. ©2017 AACR.