Proline, glutamic acid and leucine-rich protein-1 is essential for optimal p53-mediated DNA damage response

Single Amino Acid Substitution the DNA Repairing Gene Radiation-Sensitive 4 Contributes to Ultraviolet Tolerance of a Plant Pathogen

To successfully survive and reproduce, all species constantly modify the structure and expression of their genomes to cope with changing environmental conditions including ultraviolet (UV) radiation. Thus, knowledge of species adaptation to environmental changes is a central theme of evolutionary studies which could have important implication for disease management and social-ecological sustainability in the future but is generally insufficient. Here, we investigated the evolution of UV adaptation in organisms by population genetic analysis of sequence structure, physiochemistry, transcription, and fitness variation in the radiation-sensitive 4 (RAD4) gene of the Irish potato famine pathogen Phytophthora infestans sampled from various altitudes. We found that RAD4 is a key gene determining the resistance of the pathogen to UV stress as indicated by strong phenotype-genotype-geography associations and upregulated transcription after UV exposure. We also found conserved evolution in the RAD4 gene. Only five nucleotide haplotypes corresponding to three protein isoforms generated by point mutations were detected in the 140 sequences analyzed and the mutations were constrained to the N-terminal domain of the protein. Physiochemical changes associated with non-synonymous mutations generate severe fitness penalty to mutants, which are purged out by natural selection, leading to the conserved evolution observed in the gene.

PELP1 is a novel oncogene in gastric tumorigenesis and negatively regulated by miR-15 family microRNAs

BACKGROUD

Gastric cancer (GC) is one of the leading causes of cancer-related death in East Asia and some South American countries, but its mechanism has not been clarified clearly. Proline-, glutamic acid-, and leucine-rich protein-1 (PELP1), a co-regulatory molecule of estrogen receptor α (ER α), is up-regulated in series of cancers such as endometrial carcinoma, ovarian cancer, colorectal cancer, breast cancer, and non-small cell lung cancer. However, PELP1's role in GC is still obscure, and its aberrant expression in cancers also remains to be explained.

METHODS

Immunohistochemical staining and Real-time PCR were used to compare the expression level of PELP1 in GC tissues and adjacent tissues. Western blot was used to detect the expression of PELP1 in cell lines. Kaplan-meier analysis and chi-square test were applied to evaluate the potential of PELP1 to function as a cancer biomarker. RNA interference was used to inhibit PELP1 expression in GC cells, followed by detecting cell proliferation, apoptosis, migration and invasion. Luciferase assay was conducted to validate whether miR-15 family members can directly target PELP1.

RESULTS

In this study, we validated that PELP1 was significantly up-regulated in GC samples and cell lines. It was also demonstrated that the up-regulation of PELP1 was associated with several clinicopathologic features such as tumor diameter (P< 0.001), serum CEA level (P= 0.034), and lymphatic metastasis (P= 0.0009) of GC patients, and its high expression was correlated with shorter disease-free survival and overall survival of the patients. Knockdown of PELP1 remarkably arrested the proliferationï¼ migration and invasion, while promoted apoptosis. We also confirmed that miR-15 family microRNAs, most of which were down-regulated and tumor suppressor in cancers, were posttranscriptional regulators of PELP1.

CONCLUSION

In conclusion, we demonstrated that PELP1 was an oncogene of GC associated with patients' prognosis and miR-15 family members contributed to its aberrant expression in cancers.

Mouse bone marrow mesenchymal stem cells with distinct p53 statuses display differential characteristics

Mesenchymal stem cells (MSCs) affect diverse aspects of tumor progression, such as angiogenesis, tumor growth and metastasis. Bone marrow MSCs (BM‑MSCs) are fibroblast‑like cells with multipotent differentiation ability, that localize to areas of tissue damage, including wounds and solid tumors. The tumor suppressor gene, p53, is functionally involved in cell cycle control, apoptosis and genomic stability, and is mutated and inactivated in most human cancers. The present study aimed to investigate the role of p53 in the biology of BM‑MSCs. In the present study, p53 wild‑type (p53+/+), knockdown (p53+/‑) and knockout (p53‑/‑) mouse BM‑MSCs (mBM‑MSCs) were observed to be similar in appearance and in the expression of cell surface biomarkers, but expressed differential p53 protein levels. The p53+/‑ and p53‑/‑ mBM‑MSCs demonstrated an increased proliferation rate compared with mBM‑MSCs derived from p53+/+ mice. mBM‑MSCs from all three groups, representing distinct p53 statuses, were unable to form tumors over a 3‑month period in vivo. The adipogenic and osteogenic differentiation of mBM‑MSCs was increased in the absence of p53. The colony formation and migratory abilities of p53+/‑ and p53‑/‑ mBM‑MSCs were markedly enhanced, and the expression levels of stem cell‑associated proteins were significantly increased compared with p53+/+. The expression levels of microRNA (miR)‑3152 and miR‑337 were significantly increased in p53+/‑ and p53‑/‑ mBM‑MSCs, whereas the expression levels of miR‑221, miR‑155, miR‑1288 and miR‑4669 were significantly decreased. The expression levels of tumor necrosis factor‑α and interferon‑γ‑inducible protein‑10 were significantly upregulated in the supernatant of p53+/‑ and p53‑/‑ mBM‑MSCs. Ubiquitin protein ligase E3 component n‑recognin 2, RING‑finger protein 31 and matrix metalloproteinase 19 were highly expressed in p53+/‑ and p53‑/‑ mBM‑MSCs. The results of the present study indicated that p53 may serve an important role in the biology of mBM‑MSCs, and may provide novel insights into the role of cells with different p53 statuses in cancer progression.

Phosphoproteomic analysis reveals plant DNA damage signalling pathways with a functional role for histone H2AX phosphorylation in plant growth under genotoxic stress

DNA damage responses are crucial for plant growth under genotoxic stress. Accumulating evidence indicates that DNA damage responses differ between plant cell types. Here, quantitative shotgun phosphoproteomics provided high-throughput analysis of the DNA damage response network in callus cells. MS analysis revealed a wide network of highly dynamic changes in the phosphoprotein profile of genotoxin-treated cells, largely mediated by the ATAXIA TELANGIECTASIA MUTATED (ATM) protein kinase, representing candidate factors that modulate plant growth, development and DNA repair. A C-terminal dual serine target motif unique to H2AX in the plant lineage showed 171-fold phosphorylation that was absent in atm mutant lines. The physiological significance of post-translational DNA damage signalling to plant growth and survival was demonstrated using reverse genetics and complementation studies of h2ax mutants, establishing the functional role of ATM-mediated histone modification in plant growth under genotoxic stress. Our findings demonstrate the complexity and functional significance of post-translational DNA damage signalling responses in plants and establish the requirement of H2AX phosphorylation for plant survival under genotoxic stress.

PELP1 promotes glioblastoma progression by enhancing Wnt/β-catenin signaling

Background

Glioblastoma (GBM) is a deadly neoplasm of the central nervous system. The molecular mechanisms and players that contribute to GBM development is incompletely understood.

Methods

The expression of PELP1 in different grades of glioma and normal brain tissues was analyzed using immunohistochemistry on a tumor tissue array. PELP1 expression in established and primary GBM cell lines was analyzed by Western blotting. The effect of PELP1 knockdown was studied using cell proliferation, colony formation, migration, and invasion assays. Mechanistic studies were conducted using RNA-seq, RT-qPCR, immunoprecipitation, reporter gene assays, and signaling analysis. Mouse orthotopic models were used for preclinical evaluation of PELP1 knock down.

Results

Nuclear receptor coregulator PELP1 is highly expressed in gliomas compared to normal brain tissues, with the highest expression in GBM. PELP1 expression was elevated in established and patient-derived GBM cell lines compared to normal astrocytes. Knockdown of PELP1 resulted in a significant decrease in cell viability, survival, migration, and invasion. Global RNA-sequencing studies demonstrated that PELP1 knockdown significantly reduced the expression of genes involved in the Wnt/β-catenin pathway. Mechanistic studies demonstrated that PELP1 interacts with and functions as a coactivator of β-catenin. Knockdown of PELP1 resulted in a significant increase in survival of mice implanted with U87 and GBM PDX models.

Conclusions

PELP1 expression is upregulated in GBM and PELP1 signaling via β-catenin axis contributes to GBM progression. Thus, PELP1 could be a potential target for the development of therapeutic intervention in GBM.

Protective effects of dietary glycine and glutamic acid toward the toxic effects of oxidized mustard oil in rabbits

The protective role of glycine and glutamic acid against the toxic effects of oxidized oil was studied for the first time. Mustard seed oil was thermally oxidized and characterized for quality characteristics and polyphenolic composition using reversed phase HPLC-DAD. Significant changes in the quality characteristics occurred with thermal oxidation. Fourteen polyphenolic compounds were identified and quantified in oils. Quercetin-3-glucoside, quercetin-3-feruloylsophoroside, catechin, quercetin-3-rutinoside, quercetin-3,7-diglucoside, sinapic acid and vanillic acid hexoside were the major compounds in the fresh and oxidized oil. Oxidized, un-oxidized mustard oils, glycine and glutamic acid were given to rabbits alone or in combination. The biochemical responses were studied in terms of haematological and biochemical parameters and histopathology. It has been observed that biochemical and haematological parameters were adversely affected by the oxidized oil, while supplementation of both amino acids was beneficial in normalizing these parameters. Both amino acids alone have no significant effects, however, oxidized oil affected the liver by enhancing fat accumulation, causing hepatitis, reactive Kupffer cells and necrosis. The co-administration of oxidized oils with glycine or glutamic acid revealed significant recovery of the liver structure and function. In conclusion, glycine or glutamic acid is beneficial and protective against food toxicity and can be considered as an ameliorative food supplement.

PELP1: a key mediator of oestrogen signalling and actions in the brain

Proline-, glutamic acid- and leucine-rich protein 1 (PELP1) is an oestrogen receptor (ER) coregulator protein identified by our collaborative group. Work from our laboratory and others has shown that PELP1 is a scaffold protein that interacts with ERs and kinase signalling factors, as well as proteins involved in chromatin remodelling and DNA repair. Its role in mediating 17β-oestradiol (E₂ ) signalling and actions has been studied in detail in cancer cells, although only recently has attention turned to its role in the brain. In this review, we discuss the tissue, cellular and subcellular localisation of PELP1 in the brain. We also discuss recent evidence from PELP1 forebrain-specific knockout mice demonstrating a critical role of PELP1 in mediating both extranuclear and nuclear ER signalling in the brain, as well as E₂ -induced neuroprotection, anti-inflammatory effects and regulation of cognitive function. Finally, the PELP1 interactome and unique gene network regulated by PELP1 in the brain is discussed, especially because it provides new insights into PELP1 biology, protein interactions and mechanisms of action in the brain. As a whole, the findings discussed in the present review indicate that PELP1 functions as a critical ER coregulator in the brain to mediate E₂ signalling and actions.

Setdb1, a novel interactor of ΔNp63, is involved in breast tumorigenesis

ΔNp63 has been recently involved in self-renewal potential of breast cancer stem cells. Although the p63 transcriptional profile has been extensively characterized, our knowledge of the p63-binding partners potentially involved in the regulation of breast tumour progression is limited. Here, we performed the yeast two hybrid approach to identify p63α interactors involved in breast tumorigenesis and we found that SETDB1, a histone lysine methyl transferases, interacts with ΔNp63α and that this interaction contributes to p63 protein stability. SETDB1 is often amplified in primary breast tumours, and its depletion confers to breast cancer cells growth disadvantage. We identified a list of thirty genes repressed by ΔNp63 in a SETDB1-dependent manner, whose expression is positively correlated to survival of breast cancer patients. These results suggest that p63 and SETDB1 expression, together with the repressed genes, may have diagnostic and prognostic potential.

Metabolic pathways regulated by TAp73 in response to oxidative stress

Reactive oxygen species are involved in both physiological and pathological processes including neurodegeneration and cancer. Therefore, cells have developed scavenging mechanisms to maintain redox homeostasis under control. Tumor suppressor genes play a critical role in the regulation of antioxidant genes. Here, we investigated whether the tumor suppressor gene TAp73 is involved in the regulation of metabolic adaptations triggered in response to oxidative stress. H₂O₂ treatment resulted in numerous biochemical changes in both control and TAp73 knockout (TAp73−/−) mouse embryonic fibroblasts, however the extent of these changes was more pronounced in TAp73−/− cells when compared to control cells. In particular, loss of TAp73 led to alterations in glucose, nucleotide and amino acid metabolism. In addition, H₂O₂ treatment resulted in increased pentose phosphate pathway (PPP) activity in null mouse embryonic fibroblasts. Overall, our results suggest that in the absence of TAp73, H₂O₂ treatment results in an enhanced oxidative environment, and at the same time in an increased pro-anabolic phenotype. In conclusion, the metabolic profile observed reinforces the role of TAp73 as tumor suppressor and indicates that TAp73 exerts this function, at least partially, by regulation of cellular metabolism.

p73 promotes glioblastoma cell invasion by directly activating POSTN (periostin) expression

Glioblastoma Multiforme is one of the most highly metastatic cancers and constitutes 70% of all gliomas. Despite aggressive treatments these tumours have an exceptionally bad prognosis, mainly due to therapy resistance and tumour recurrence. Here we show that the transcription factor p73 confers an invasive phenotype by directly activating expression of POSTN (periostin, HGNC:16953) in glioblastoma cells. Knock down of endogenous p73 reduces invasiveness and chemo-resistance, and promotes differentiation in vitro. Using chromatin immunoprecipitation and reporter assays we demonstrate that POSTN, an integrin binding protein that has recently been shown to play a major role in metastasis, is a transcriptional target of TAp73. We further show that POSTN overexpression is sufficient to rescue the invasive phenotype of glioblastoma cells after p73 knock down. Additionally, bioinformatics analysis revealed that an intact p73/POSTN axis, where POSTN and p73 expression is correlated, predicts bad prognosis in several cancer types. Taken together, our results support a novel role of TAp73 in controlling glioblastoma cell invasion by regulating the expression of the matricellular protein POSTN.

Ultraconserved long non-coding RNA uc.63 in breast cancer

Transcribed-ultraconserved regions (T-UCRs) are long non-coding RNAs (lncRNA) encoded by a subset of long ultraconserved stretches in the human genome. Recent studies revealed that the expression of several T-UCRs is altered in cancer and growing evidences underline the importance of T-UCRs in oncogenesis, offering also potential new strategies for diagnosis and prognosis. We found that overexpression of one specific T-UCRs named uc.63 is associated with bad outcome in luminal A subtype of breast cancer patients. uc.63 is localized in the third intron of exportin-1 gene (XPO1) and is transcribed in the same orientation of its host gene. Interestingly, silencing of uc.63 induces apoptosis in vitro. However, silencing of host gene XPO1 does not cause the same effect suggesting that the transcription of uc.63 is independent of XPO1. Our results reveal an important role of uc.63 in promoting breast cancer cells survival and offer the prospect to identify a signature associated with poor prognosis.

Differential regulated microRNA by wild type and mutant p53 in induced pluripotent stem cells

The tumour suppressor p53 plays an important role in somatic cell reprogramming. While wild-type p53 reduces reprogramming efficiency, mutant p53 exerts a gain of function activity that leads to increased reprogramming efficiency. Furthermore, induced pluripotent stem cells expressing mutant p53 lose their pluripotency in vivo and form malignant tumours when injected in mice. It is therefore of great interest to identify targets of p53 (wild type and mutant) that are responsible for this phenotype during reprogramming, as these could be exploited for therapeutic use, that is, formation of induced pluripotent stem cells with high reprogramming efficiency, but no oncogenic potential. Here we studied the transcriptional changes of microRNA in a series of mouse embryonic fibroblasts that have undergone transition to induced pluripotent stem cells with wild type, knock out or mutant p53 status in order to identify microRNAs whose expression during reprogramming is dependent on p53. We identified a number of microRNAs, with known functions in differentiation and carcinogenesis, the expression of which was dependent on the p53 status of the cells. Furthermore, we detected several uncharacterised microRNAs that were regulated differentially in the different p53 backgrounds, suggesting a novel role of these microRNAs in reprogramming and pluripotency.

DNA repair and aging: the impact of the p53 family

Cells are constantly exposed to endogenous and exogenous factors that threaten the integrity of their DNA. The maintenance of genome stability is of paramount importance in the prevention of both cancer and aging processes. To deal with DNA damage, cells put into operation a sophisticated and coordinated mechanism, collectively known as DNA damage response (DDR). The DDR orchestrates different cellular processes, such as DNA repair, senescence and apoptosis. Among the key factors of the DDR, the related proteins p53, p63 and p73, all belonging to the same family of transcription factors, play multiple relevant roles. Indeed, the members of this family are directly involved in the induction of cell cycle arrest that is necessary to allow the cells to repair. Alternatively, they can promote cell death in case of prolonged or irreparable DNA damage. They also take part in a more direct task by modulating the expression of core factors involved in the process of DNA repair or by directly interacting with them. In this review we will analyze the fundamental roles of the p53 family in the aging process through their multifaceted function in DDR.

Acetylation-regulated interaction between p53 and SET reveals a widespread regulatory mode

Although lysine acetylation is now recognized as a general protein modification for both histones and non-histone proteins^1-3, the mechanisms of acetylation mediated actions are not completely understood. Acetylation of the C-terminal domain (CTD) of p53 was the first example for non-histone protein acetylation⁴. Yet the precise role of the CTD acetylation remains elusive. Lysine acetylation often creates binding sites for bromodomain-containing “reader” proteins^5,6; surprisingly, in a proteomic screen, we identified SET as a major cellular factor whose binding with p53 is totally dependent on the CTD acetylation status. SET profoundly inhibits p53 transcriptional activity in unstressed cells but SET-mediated repression is completely abolished by stress-induced p53 CTD acetylation. Moreover, loss of the interaction with SET activates p53, resulting in tumor regression in mouse xenograft models. Notably, the acidic domain of SET acts as a “reader” for unacetylated CTD of p53 and this mechanism of acetylation-dependent regulation is widespread in nature. For example, p53 acetylation also modulates its interactions with similar acidic domains found in other p53 regulators including VPRBP, DAXX and PELP1 (refs. 7-9), and computational analysis of the proteome identified numerous proteins with the potential to serve as the acidic domain readers and lysine-rich ligands. Unlike bromodomain readers, which preferentially bind the acetylated forms of their cognate ligands, the acidic domain readers specifically recognize the unacetylated forms of their ligands. Finally, the acetylation-dependent regulation of p53 was further validated in vivo by using a knockin mouse model expressing an acetylation-mimicking form of p53. These results reveal that the acidic domain-containing factors act as a new class of acetylation-dependent regulators by targeting p53 and potentially, beyond.

Anti-tumoral effect of desmethylclomipramine in lung cancer stem cells

Lung cancer is the most feared of all cancers because of its heterogeneity and resistance to available treatments. Cancer stem cells (CSCs) are the cell population responsible for lung cancer chemoresistance and are a very good model for testing new targeted therapies. Clomipramine is an FDA-approved antidepressant drug, able to inhibit in vitro the E3 ubiquitin ligase Itch and potentiate the pro-apoptotic effects of DNA damaging induced agents in several cancer cell lines. Here, we investigated the potential therapeutic effect of desmethylclomipramine (DCMI), the active metabolite of Clomipramine, on the CSCs homeostasis. We show that DCMI inhibits lung CSCs growth, decreases their stemness potential and increases the cytotoxic effect of conventional chemotherapeutic drugs. Being DCMI an inhibitor of the E3 ubiquitin ligase Itch, we also verified the effect of Itch deregulation on CSCs survival. We found that the siRNA-mediated depletion of Itch induces similar anti-proliferative effects on lung CSCs, suggesting that DCMI might exert its effect, at least in part, by inhibiting Itch. Notably, Itch expression is a negative prognostic factor in two primary lung tumors datasets, supporting the potential clinical relevance of Itch inhibition to circumvent drug resistance in the treatment of lung cancer.

PELP1: Structure, biological function and clinical significance

Proline-, glutamic acid-, and leucine-rich protein 1 (PELP1) is a scaffolding protein that functions as a coregulator of several transcription factors and nuclear receptors. Notably, the PELP1 protein has a histone-binding domain, recognizes histone modifications and interacts with several chromatin-modifying complexes. PELP1 serves as a substrate of multitude of kinases, and phosphorylation regulates its functions in various complexes. Further, PELP1 plays essential roles in several pathways including hormonal signaling, cell cycle progression, ribosomal biogenesis, and the DNA damage response. PELP1 expression is upregulated in several cancers, its deregulation contributes to therapy resistance, and it is a prognostic biomarker for breast cancer survival. Recent evidence suggests that PELP1 represents a novel therapeutic target for many hormonal cancers. In this review, we summarized the emerging biological properties and functions of PELP1.

P53 functional abnormality in mesenchymal stem cells promotes osteosarcoma development

It has been shown that p53 has a critical role in the differentiation and functionality of various multipotent progenitor cells. P53 mutations can lead to genome instability and subsequent functional alterations and aberrant transformation of mesenchymal stem cells (MSCs). The significance of p53 in safeguarding our body from developing osteosarcoma (OS) is well recognized. During bone remodeling, p53 has a key role in negatively regulating key factors orchestrating the early stages of osteogenic differentiation of MSCs. Interestingly, changes in the p53 status can compromise bone homeostasis and affect the tumor microenvironment. This review aims to provide a unique opportunity to study the p53 function in MSCs and OS. In the context of loss of function of p53, we provide a model for two sources of OS: MSCs as progenitor cells of osteoblasts and bone tumor microenvironment components. Standing at the bone remodeling point of view, in this review we will first explain the determinant function of p53 in OS development. We will then summarize the role of p53 in monitoring MSC fidelity and in regulating MSC differentiation programs during osteogenesis. Finally, we will discuss the importance of loss of p53 function in tissue microenvironment. We expect that the information provided herein could lead to better understanding and treatment of OS.

Neuroblastoma: oncogenic mechanisms and therapeutic exploitation of necroptosis

Neuroblastoma (NB) is the most common extracranial childhood tumor classified in five stages (1, 2, 3, 4 and 4S), two of which (3 and 4) identify chemotherapy-resistant, highly aggressive disease. High-risk NB frequently displays MYCN amplification, mutations in ALK and ATRX, and genomic rearrangements in TERT genes. These NB subtypes are also characterized by reduced susceptibility to programmed cell death induced by chemotherapeutic drugs. The latter feature is a major cause of failure in the treatment of advanced NB patients. Thus, proper reactivation of apoptosis or of other types of programmed cell death pathways in response to treatment is relevant for the clinical management of aggressive forms of NB. In this short review, we will discuss the most relevant genomic rearrangements that define high-risk NB and the role that destabilization of p53 and p73 can have in NB aggressiveness. In addition, we will propose a strategy to stabilize p53 and p73 by using specific inhibitors of their ubiquitin-dependent degradation. Finally, we will introduce necroptosis as an alternative strategy to kill NB cells and increase tumor immunogenicity.

The p53 tetramer shows an induced-fit interaction of the C-terminal domain with the DNA-binding domain

The Trp53 gene is the most frequently mutated gene in all human cancers. Its protein product p53 is a very powerful transcription factor that can activate different biochemical pathways and affect the regulation of metabolism, senescence, DNA damage response, cell cycle and cell death. The understanding of its function at the molecular level could be of pivotal relevance for therapy. Investigation of long-range intra- and interdomain communications in the p53 tetramer–DNA complex was performed by means of an atomistic model that included the tetramerization helices in the C-terminal domain, the DNA-binding domains and a consensus DNA-binding site of 18 base pairs. Nonsymmetric dynamics are illustrated in the four DNA-binding domains, with loop L1 switching from inward to outward conformations with respect to the DNA major groove. Direct intra- and intermonomeric long-range communications between the tetramerization and DNA-binding domains are noted. These long-distance conformational changes link the C terminus with the DNA-binding domain and provide a biophysical rationale for the reported functional regulation of the p53 C-terminal region. A fine characterization of the DNA deformation caused by p53 binding is obtained, with ‘static' deformations always present and measured by the slide parameter in the central thymine–adenine base pairs; we also detect ‘dynamic' deformations switched on and off by particular p53 tetrameric conformations and measured by the roll and twist parameters in the same base pairs. These different conformations can indeed modulate the electrostatic potential isosurfaces of the whole p53–DNA complex. These results provide a molecular/biophysical understanding of the evident role of the C terminus in post-translational modification that regulates the transcriptional function of p53. Furthermore, the unstructured C terminus is able to facilitate contacts between the core DNA-binding domains of the tetramer.

Amino-terminal residues of ΔNp63, mutated in ectodermal dysplasia, are required for its transcriptional activity

p63, a member of the p53 family, is a crucial transcription factor for epithelial development and skin homeostasis. Heterozygous mutations in TP63 gene have been associated with human ectodermal dysplasia disorders. Most of these TP63 mutations are missense mutations causing amino acidic substitutions at p63 DNA binding or SAM domains that reduce or abolish the transcriptional activity of mutants p63. A significant number of mutants, however, resides in part of the p63 protein that apparently do not affect DNA binding and/or transcriptional activity, such as the N-terminal domain. Here, we characterize five p63 mutations at the 5' end of TP63 gene aiming to understand the pathogenesis of the diseases and to uncover the role of ΔNp63α N-terminus residues in determining its transactivation potential.

TAp73 transcriptionally represses BNIP3 expression

TAp73 is a tumor suppressor transcriptional factor, belonging to p53 family. Alteration of TAp73 in tumors might lead to reduced DNA damage response, cell cycle arrest and apoptosis. Carcinogen-induced TAp73(-/-) tumors display also increased angiogenesis, associated to hyperactivition of hypoxia inducible factor signaling. Here, we show that TAp73 suppresses BNIP3 expression, directly binding its gene promoter. BNIP3 is a hypoxia responsive protein, involved in a variety of cellular processes, such as autophagy, mitophagy, apoptosis and necrotic-like cell death. Therefore, through different cellular process altered expression of BNIP3 may differently contribute to cancer development and progression. We found a significant upregulation of BNIP3 in human lung cancer datasets, and we identified a direct association between BNIP3 expression and survival rate of lung cancer patients. Our data therefore provide a novel transcriptional target of TAp73, associated to its antagonistic role on HIF signaling in cancer, which might play a role in tumor suppression.

Novel role of PELP1 in regulating chemotherapy response in mutant p53-expressing triple negative breast cancer cells

Triple-negative breast cancer (TNBC), the most aggressive breast cancer subtype, occurs in younger women and is associated with poor prognosis. Gain-of-function mutations in TP53 are a frequent occurrence in TNBC and have been demonstrated to repress apoptosis and up-regulate cell cycle progression. Even though TNBC responds to initial chemotherapy, resistance to chemotherapy develops and is a major clinical problem. Tumor recurrence eventually occurs and most patients die from their disease. An urgent need exists to identify molecular-targeted therapies that can enhance chemotherapy response. In the present study, we report that targeting PELP1, an oncogenic co-regulator molecule, could enhance the chemotherapeutic response of TNBC through the inhibition of cell cycle progression and activation of apoptosis. We demonstrate that PELP1 interacts with MTp53, regulates its recruitment, and alters epigenetic marks at the target gene promoters. PELP1 knockdown reduced MTp53 target gene expression, resulting in decreased cell survival and increased apoptosis upon genotoxic stress. Mechanistic studies revealed that PELP1 depletion contributes to increased stability of E2F1, a transcription factor that regulates both cell cycle and apoptosis in a context-dependent manner. Further, PELP1 regulates E2F1 stability in a KDM1A-dependent manner, and PELP1 phosphorylation at the S1033 residue plays an important role in mediating its oncogenic functions in TNBC cells. Accordingly, depletion of PELP1 increased the expression of E2F1 target genes and reduced TNBC cell survival in response to genotoxic agents. PELP1 phosphorylation was significantly greater in the TNBC tumors than in the other subtypes of breast cancer and in the normal tissues. These findings suggest that PELP1 is an important molecular target in TNBC, and that PELP1-targeted therapies may enhance response to chemotherapies.

Dose-dependent metabolic alterations in human cells exposed to gamma irradiation

Radiation exposure is a threat to public health because it causes many diseases, such as cancers and birth defects, due to genetic modification of cells. Compared with the past, a greater number of people are more frequently exposed to higher levels of radioactivity today, not least due to the increased use of diagnostic and therapeutic radiation-emitting devices. In this study, ultra-performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UPLC-QTOF-MS)-based metabolic profiling was used to investigate radiation- induced metabolic changes in human fibroblasts. After exposure to 1 and 5 Gy of γ-radiation, the irradiated fibroblasts were harvested at 24, 48, and 72 h and subjected to global metabolite profiling analysis. Mass spectral peaks of cell extracts were analyzed by pattern recognition using principal component analysis (PCA) and partial least squares-discriminant analysis (PLS-DA). The results showed that the cells irradiated with 1 Gy returned to control levels at 72 h post radiation, whereas cells irradiated with 5 Gy were quite unlike the controls; therefore, cells irradiated with 1 Gy had recovered, whereas those irradiated with 5 Gy had not. Lipid and amino acid levels increased after the higher-level radiation, indicating degradation of membranes and proteins. These results suggest that MS-based metabolite profiling of γ-radiation-exposed human cells provides insight into the global metabolic alterations in these cells.

PELP1 overexpression in the mouse mammary gland results in the development of hyperplasia and carcinoma

Estrogen receptor (ER) coregulator overexpression promotes carcinogenesis and/or progression of endocrine related-cancers in which steroid hormones are powerful mitogenic agents. Recent studies in our laboratory, as well as others, demonstrated that the estrogen receptor coregulator PELP1 is a proto-oncogene. PELP1 interactions with histone demethylase KDM1 play a critical role in its oncogenic functions and PELP1 is a prognostic indicator of decreased survival in patients with breast cancer. However, the in vivo significance of PELP1 deregulation during initiation and progression of breast cancer remains unknown. We generated an inducible, mammary gland-specific PELP1-expressing transgenic (Tg) mouse (MMTVrtTA-TetOPELP1). We found more proliferation, extensive side branching, and precocious differentiation in PELP1-overexpressing mammary glands than in control glands. Aged MMTVrtTA-TetOPELP1 Tg mice had hyperplasia and preneoplastic changes as early as 12 weeks, and ER-positive mammary tumors occurred at a latency of 14 to 16 months. Mechanistic studies revealed that PELP1 deregulation altered expression of a number of known ER target genes involved in cellular proliferation (cyclin D1, CDKs) and morphogenesis (EGFR, MMPs) and such changes facilitated altered mammary gland morphogenesis and tumor progression. Furthermore, PELP1 was hyper-phosphorylated at its CDK phosphorylation site, suggesting an autocrine loop involving the CDK-cyclin D1-PELP1 axis in promoting mammary tumorigenesis. Treatment of PELP1 Tg mice with a KDM1 inhibitor significantly reduced PELP1-driven hyperbranching, reversed alterations in cyclin D1 expression levels, and reduced CDK-driven PELP1 phosphorylation. These results further support the hypothesis that PELP1 deregulation has the potential to promote breast tumorigenesis in vivo and represent a novel model for future investigation into molecular mechanisms of PELP1-mediated tumorigenesis.