GADD45A: With or without you.

The growth arrest and DNA damage inducible (GADD)45 family includes three small and ubiquitously distributed proteins (GADD45A, GADD45B, and GADD45G) that regulate numerous cellular processes associated with stress signaling and injury response. Here, we provide a comprehensive review of the current literature investigating GADD45A, the first discovered member of the family. We first depict how its levels are regulated by a myriad of genotoxic and non-genotoxic stressors, and through the combined action of intricate transcriptional, posttranscriptional, and even, posttranslational mechanisms. GADD45A is a recognized tumor suppressor and, for this reason, we next summarize its role in cancer, as well as the different mechanisms by which it regulates cell cycle, DNA repair, and apoptosis. Beyond these most well-known actions, GADD45A may also influence catabolic and anabolic pathways in the liver, adipose tissue and skeletal muscle, among others. Not surprisingly, GADD45A may trigger AMP-activated protein kinase activity, a master regulator of metabolism, and is known to act as a transcriptional coregulator of numerous nuclear receptors. GADD45A has also been reported to display a cytoprotective role by regulating inflammation, fibrosis and oxidative stress in several organs and tissues, and is regarded an important contributor for the development of heart failure. Overall data point to that GADD45A may play an important role in metabolic, neurodegenerative and cardiovascular diseases, and also autoimmune-related disorders. Thus, the potential mechanisms by which dysregulation of GADD45A activity may contribute to the progression of these diseases are also reviewed below.

Aristolochic acids-hijacked p53 promotes liver cancer cell growth by inhibiting ferroptosis.

Aristolochic acids (AAs) have been identified as a significant risk factor for hepatocellular carcinoma (HCC). Ferroptosis is a type of regulated cell death involved in the tumor development. In this study, we investigated the molecular mechanisms by which AAs enhanced the growth of HCC. By conducting bioinformatics and RNA-Seq analyses, we found that AAs were closely correlated with ferroptosis. The physical interaction between p53 and AAs in HepG2 cells was validated by bioinformatics analysis and SPR assays with the binding pocket sites containing Pro92, Arg174, Asp207, Phe212, and His214 of p53. Based on the binding pocket that interacts with AAs, we designed a mutant and performed RNA-Seq profiling. Interestingly, we found that the binding pocket was responsible for ferroptosis, GADD45A, NRF2, and SLC7A11. Functionally, the interaction disturbed the binding of p53 to the promoter of GADD45A or NRF2, attenuating the role of p53 in enhancing GADD45A and suppressing NRF2; the mutant did not exhibit the same effects. Consequently, this event down-regulated GADD45A and up-regulated NRF2, ultimately inhibiting ferroptosis, suggesting that AAs hijacked p53 to down-regulate GADD45A and up-regulate NRF2 in HepG2 cells. Thus, AAs treatment resulted in the inhibition of ferroptosis via the p53/GADD45A/NRF2/SLC7A11 axis, which led to the enhancement of tumor growth. In conclusion, AAs-hijacked p53 restrains ferroptosis through the GADD45A/NRF2/SLC7A11 axis to enhance tumor growth. Our findings provide an underlying mechanism by which AAs enhance HCC and new insights into p53 in liver cancer. Therapeutically, the oncogene NRF2 is a promising target for liver cancer.

OsGADD45a1: a multifaceted regulator of rice architecture, grain yield, and blast resistance.

KEY MESSAGE: The homolog gene of the Growth Arrest and DNA Damage-inducible 45 (GADD45) in rice functions in the regulation of plant architecture, grain yield, and blast resistance. The Growth Arrest and DNA Damage-inducible 45 (GADD45) family proteins, well-established stress sensors and tumor suppressors in mammals, serve as pivotal regulators of genotoxic stress responses and tumorigenesis. In contrast, the homolog and role of GADD45 in plants have remained unclear. Herein, using forward genetics, we identified an activation tagging mutant AC13 exhibited dwarf characteristics resulting from the loss-of-function of the rice GADD45α homolog, denoted as OsGADD45a1. osgadd45a1 mutants displayed reduced plant height, shortened panicle length, and decreased grain yield compared to the wild-type Kitaake. Conversely, no obvious differences in plant height, panicle length, or grain yield were observed between wild-type and OsGADD45a1 overexpression plants. OsGADD45a1 displayed relatively high expression in germinated seeds and panicles, with localization in both the nucleus and cytoplasm. RNA-sequencing analysis suggested a potential role for OsGADD45a1 in the regulation of photosynthesis, and binding partner identification indicates OsGADD45a1 interacts with OsRML1 to regulate rice growth. Intriguingly, our study unveiled a novel role for OsGADD45a1 in rice blast resistance, as osgadd45a1 mutant showed enhanced resistance to Magnaporthe oryzae, and the expression of OsGADD45a1 was diminished upon blast fungus treatment. The involvement of OsGADD45a1 in rice blast fungus resistance presents a groundbreaking finding. In summary, our results shed light on the multifaceted role of OsGADD45a1 in rice, encompassing biotic stress response and the modulation of several agricultural traits, including plant height, panicle length, and grain yield.

GADD45A regulates subcutaneous fat deposition and lipid metabolism by interacting with Stat1.

BACKGROUND: Obesity, characterized by excessive white adipose tissue expansion, is associated with several metabolic complications. Identifying new adipogenesis regulators may lead to effective therapies for obesity-induced metabolic disorders. RESULTS: Here, we identified the growth arrest and DNA damage-inducible A (GADD45A), a stress-inducible histone-folding protein, as a novel regulator of subcutaneous adipose metabolism. We found that GADD45A expression was positively correlated with subcutaneous fat deposition and obesity in humans and fatty animals. In vitro, the gain or loss function of GADD45A promoted or inhibited subcutaneous adipogenic differentiation and lipid accumulation, respectively. Using a Gadd45a-/- mouse model, we showed that compared to wild-type (WT) mice, knockout (KO) mice exhibited subcutaneous fat browning and resistance to high-fat diet (HFD)-induced obesity. GADD45A deletion also upregulated the expression of mitochondria-related genes. Importantly, we further revealed that the interaction of GADD45A with Stat1 prevented phosphorylation of Stat1, resulting in the impaired expression of Lkb1, thereby regulating subcutaneous adipogenesis and lipid metabolism. CONCLUSIONS: Overall, our results reveal the critical regulatory roles of GADD45A in subcutaneous fat deposition and lipid metabolism. We demonstrate that GADD45A deficiency induces the inguinal white adipose tissue (iWAT) browning and protects mice against HFD-induced obesity. Our findings provide new potential targets for combating obesity-related metabolic diseases and improving human health.

Deletion of Gadd45a Expression in Mice Leads to Cognitive and Synaptic Impairment Associated with Alzheimer's Disease Hallmarks.

Gadd45 genes have been implicated in survival mechanisms, including apoptosis, autophagy, cell cycle arrest, and DNA repair, which are processes related to aging and life span. Here, we analyzed if the deletion of Gadd45a activates pathways involved in neurodegenerative disorders such as Alzheimer's Disease (AD). This study used wild-type (WT) and Gadd45a knockout (Gadd45a-/-) mice to evaluate AD progression. Behavioral tests showed that Gadd45a-/- mice presented lower working and spatial memory, pointing out an apparent cognitive impairment compared with WT animals, accompanied by an increase in Tau hyperphosphorylation and the levels of kinases involved in its phosphorylation in the hippocampus. Moreover, Gadd45a-/- animals significantly increased the brain's pro-inflammatory cytokines and modified autophagy markers. Notably, neurotrophins and the dendritic spine length of the neurons were reduced in Gadd45a-/- mice, which could contribute to the cognitive alterations observed in these animals. Overall, these findings demonstrate that the lack of the Gadd45a gene activates several pathways that exacerbate AD pathology, suggesting that promoting this protein's expression or function might be a promising therapeutic strategy to slow down AD progression.

BBOX1-AS1 mediates trophoblast cells dysfunction via regulating hnRNPK/GADD45A axis†.

Recurrent pregnancy loss (RPL) is a common pathological problem during pregnancy, and its clinical etiology is complex and unclear. Dysfunction of trophoblasts may cause a series of pregnancy complications, including preeclampsia, fetal growth restriction, and RPL. Recently, lncRNAs have been found to be closely related to the occurrence and regulation of pregnancy-related diseases, but few studies have focused on their role in RPL. In this study, we identified a novel lncRNA BBOX1-AS1 that was significantly upregulated in villous tissues and serum of RPL patients. Functionally, BBOX1-AS1 inhibited proliferation, migration, invasion, tube formation and promoted apoptosis of trophoblast cells. Mechanistically, overexpression of BBOX1-AS1 activated the p38 and JNK MAPK signaling pathways by upregulating GADD45A expression. Further studies indicated that BBOX1-AS1 could increase the stability of GADD45A mRNA by binding hnRNPK and ultimately cause abnormal trophoblast function. Collectively, our study highlights that the BBOX1-AS1/hnRNPK/GADD45A axis plays an important role in trophoblast-induced RPL and that BBOX1-AS1 may serve as a potential target for the diagnosis of RPL.

Genotoxic stress response: What is the role of cytoplasmic mRNA fate?

Genotoxic stress leads to DNA damage which can be detrimental to the cell. A well-orchestrated cellular response is mounted to manage and repair the genotoxic stress-induced DNA damage. Our understanding of genotoxic stress response is derived mainly from studies focused on transcription, mRNA splicing, and protein turnover. Surprisingly not as much is understood about the role of mRNA translation and decay in genotoxic stress response. This is despite the fact that regulation of gene expression at the level of mRNA translation and decay plays a critical role in a myriad of cellular processes. This review aims to summarize some of the known findings of the role of mRNA translation and decay by focusing on two categories of examples. We discuss examples of mRNA whose fates are regulated in the cytoplasm and RNA-binding proteins that regulate mRNA fates in response to genotoxic stress.

GADD45A and GADD45B as Novel Biomarkers Associated with Chromatin Regulators in Renal Ischemia-Reperfusion Injury.

Chromatin regulators (CRs) are essential upstream regulatory factors of epigenetic modification. The role of CRs in the pathogenesis of renal ischemia-reperfusion injury (IRI) remains unclear. We analyzed a bioinformatic analysis on the differentially expressed chromatin regulator genes in renal IRI patients using data from public domains. The hub CRs identified were used to develop a risk prediction model for renal IRI, and their expressions were also validated using Western blot, qRT-PCR, and immunohistochemistry in a murine renal IRI model. We also examined the relationships between hub CRs and infiltrating immune cells in renal IRI and used network analysis to explore drugs that target hub CRs and their relevant downstream microRNAs. The results of machine learning methods showed that five genes (DUSP1, GADD45A, GADD45B, GADD45G, HSPA1A) were upregulated in renal IRI, with key roles in the cell cycle, p38 MAPK signaling pathway, p53 signaling pathway, FoxO signaling pathway, and NF-κB signaling pathway. Two genes from the network, GADD45A and GADD45B (growth arrest and DNA damage-inducible protein 45 alpha and beta), were chosen for the renal IRI risk prediction model. They all showed good performance in the testing and validation cohorts. Mice with renal IRI showed significantly upregulated GADD45A and GADD45B expression within kidneys compared to sham-operated mice. GADD45A and GADD45B showed correlations with plasmacytoid dendritic cells (pDCs) in infiltrating immune cell analysis and enrichment in the MAPK pathway based on the weighted gene co-expression network analysis (WGCNA) method. Candidate drugs that target GADD45A and GADD45B include beta-escin, sertraline, primaquine, pimozide, and azacyclonol. The dysregulation of GADD45A and GADD45B is related to renal IRI and the infiltration of pDCs, and drugs that target GADD45A and GADD45B may have therapeutic potential for renal IRI.

Tanshinol inhibits trophoblast cell migration and invasion by regulating Gadd45a in preeclampsia.

OBJECTIVE: Tanshinol is an active constituent of Salvia miltiorrhiza that possesses anti-inflammatory, antioxidant, and antibacterial activities. Therefore, this study attempted to detect whether it has a role in the treatment of preeclampsia (PE). METHODS: In this study, we explored the effect of tanshinol on the development of PE at the cellular level. The effect of tanshinol on cell proliferation was measured by colony formation and EdU assays. The migration, invasion, and in vitro angiogenesis of HTR-8/SVneo cells were detected by wound-healing, transwell, and tube formation assays, respectively. In addition, a PE cell model was established by overexpression of Gadd45a, and this cell model was assessed with the optimal concentration of tanshinol. RESULTS: The results show that tanshinol enhanced proliferation, migration, invasion, and tube formation of HTR-8/SVneo cells in vitro. Furthermore, the reduction in proliferation, migration, invasion, and tube formation of cells by Gadd45a overexpression was partially reversed by tanshinol treatment. Tanshinol also inhibited the apoptosis of HTR-8/SVneo cells transfected with Gadd45a. CONCLUSIONS: In summary, tanshinol promoted proliferation, migration, invasion, and tube formation and inhibited the apoptosis of HTR-8/SVneo cells. It may be a novel therapeutic compound to attenuate the development of PE.

Traditional Chinese medicine has maintained the health of people in Asia for thousands of years and is increasingly used worldwide. Tanshinol has been found to be useful in the treatment and prevention of many diseases. Through experiments, we found that tanshinol is a novel therapeutic compound that promotes the proliferation, migration, invasion and tubular formation of HTR-8/SVneo cells. In addition, tanshinol also inhibited the apoptosis rate of preeclampsia cell models. Follow-up experiments will further validate the results of this study.

Molecular basis for RASSF10/NPM/RNF2 feedback cascade-mediated regulation of gastric cancer cell proliferation.

Ras-association domain family (RASSF) proteins are encoded by numerous tumor suppressor genes that frequently become silenced in human cancers. RASSF10 is downregulated by promoter hypermethylation in cancers and has been shown to inhibit cell proliferation; however, the molecular mechanism(s) remains poorly understood. Here, we demonstrate for the first time that RASSF10 inhibits Cdk1/cyclin-B kinase complex formation to maintain stable levels of cyclin-B for inducing mitotic arrest during cell cycle. Using LC-MS/MS, live cell imaging, and biochemical approaches, we identify Nucleophosmin (NPM) as a novel functional target of RASSF10 and revealed that RASSF10 expression promoted the nuclear accumulation of GADD45a and knockdown of either NPM or GADD45a, resulting in impairment of RASSF10-mediated G2/M phase arrest. Furthermore, we demonstrate that RASSF10 is a substrate for the E3 ligase ring finger protein 2 (RNF2) and show that an NPM-dependent downregulation of RNF2 expression is critical to maintain stable RASSF10 levels in cells for efficient mitotic arrest. Interestingly, the Kaplan-Meier plot analysis shows a positive correlation of RASSF10 and NPM expression with greater gastric cancer patient survival and the reverse with expression of RNF2, suggesting that they may have a role in cancer progression. Finally, our findings provide insights into the mode of action of the RASSF10/NPM/RNF2 signaling cascade on controlling cell proliferation and may represent a novel therapeutic avenue for the prevention of gastric cancer metastasis.

Gadd45 in Senescence.

Gadd45a, Gadd45b, and Gadd45g have been implicated in cell cycle arrest, DNA repair, apoptosis, innate immunity, genomic stability, and more recently in senescence. Evidence has accumulated that Gadd45a deficiency results in escape of mouse embryo fibroblasts from senescence, whereas Gadd45b deficiency promotes premature senescence and skin aging. Moreover, recently Gadd45b deficiency was found to promote senescence and attenuate liver fibrosis, whereas Gadd45a was observed to exert a protective effect against hepatic fibrosis. These findings indicate that the Gadd45 stress response proteins play important roles in modulating cellular responses to senescence. Thus, exploring how Gadd45 proteins modulate cellular senescence has the potential to provide new and innovative tools to treat cancer as well as liver disease.

Gadd45 in Preeclampsia.

Preeclampsia is a pregnancy-induced complex of multiple pathological changes. Numerous stresses during pregnancy, including hypoxia, immune activation, inflammatory cytokines, and oxidative stress were reported as contributing factors to the preeclamptic pathology. Seeking common sensors of various stressors in preeclampsia is of new interest and can potentially benefit in disease prevention and treatment. Recent studies have highlighted the role of the Gadd45a protein as a stress sensor in preeclampsia. In response to various pathophysiological stressors, notably hypoxia, oxidative stress, inflammatory cytokines, and AT1-AAs, Gadd45a activates Mkk3-p38 and or JNK signaling. This, in turn, results in immunological and inflammatory changes as well as triggering the production of circulating factors such as sFlt-1, which are believed to account for many of the pathophysiological-related symptoms of preeclampsia. Activation of inflammatory/immune responses in preeclampsia may function in a feedback loop to maintain elevated expression of Gadd45a protein.

Salinomycin induces cell cycle arrest and apoptosis and modulates hepatic cytochrome P450 mRNA expression in HepG2/C3a cells.

Salinomycin (SAL) is a monocarboxylic polyether ionophore antibiotic isolated from Streptomyces albus. It exhibits an effective antitumor potential against numerous human cancer cells. This study aimed to assess the antiproliferative effects of SAL in human hepatocellular carcinoma HepG2/C3a cell line. We investigated the effects of SAL on cell growth, DNA damage induction, cell cycle changes and apoptosis; and relative changes in expression of cell cycle-related, apoptosis-related, and CYP450 genes. SAL induced cell cycle arrest in the G2/M phase, upregulation of CDKN1A and GADD45A and downregulation of cyclin genes including CCNB1 and CCNA2. SAL effectively suppressed mRNA levels of CTNNB1 gene, an important oncogene that promotes tumorigenesis. The decrease of HepG2/C3A cells' survival can also be due to downregulation of antiapoptotic BCL-2 expression, thus promoting the induction of apoptosis by SAL. This study also demonstrated the ability of SAL in modulating hepatic cytochrome P450 (CYP) mRNA expression, such that SAL caused the upregulation of CYP1A members and CYP3A5; and downregulation of CYP3A4. Taken together, these data contribute to the understanding of the mechanism of action of SAL, highlighting that metabolizing enzymes modulated by SAL can interfere with chemotherapy treatment and it must be considered in associated treatments.

Function of DHX33 in promoting Warburg effect via regulation of glycolytic genes.

Cancer cells metabolize glucose through glycolysis to promote cell proliferation even with abundant oxygen. Multiple glycolysis genes are deregulated during cancer development. Despite intensive effort, the cause of their deregulation remains incompletely understood. Here in this study, we discovered that DHX33 plays a critical role in Warburg effect of cancer cells. DHX33 deficient cells have markedly reduced glycolysis activity. Through RNA-seq analysis, we found multiple critical genes involved in Warburg effect were downregulated after DHX33 deficiency. These genes include lactate dehydrogenase A (LDHA), pyruvate dehydrogenase kinase 1 (PDK1), pyruvate kinase muscle isoform 2 (PKM2), enolase 1 (ENO1), ENO2, hexokinase 1/2, among others. With LDHA, PDK1, and PKM2 as examples, we further revealed that DHX33 altered the epigenetic marks around the promoter of glycolytic genes. This is through DHX33 in complex with Gadd45a-a growth arrest and DNA damage protein. DHX33 is required for the loading of Gadd45a and DNA dioxygenase Tet1 at the promoter sites, which resulted in active DNA demethylation and enhanced histone H4 acetylation. We conclude that DHX33 changes local epigenetic marks in favor of the transcription of glycolysis genes to promote cancer cell proliferation. Our study highlights the significance of RNA helicase DHX33 in Warburg effect and cancer therapeutics.

Silencing lncRNA-DGCR5 increased trophoblast cell migration, invasion and tube formation, and inhibited cell apoptosis via targeting miR-454-3p/GADD45A axis.

Long noncoding RNA (lncRNA)-DGCR5 has been recognized as a potential tumor progression regulator, while its expression and specific functions in preeclampsia (PE) development remain unveiled. The expressions of miR-454-3p, lncRNA-DiGeorge syndrome critical region gene 5 (DGCR5) and growth arrest and DNA damage protein-inducible 45A (GADD45A) in placental tissues from PE patients or HTR-8/SVneo cells were assessed by Western blot or qRT-PCR. Dual-luciferase reporter assay determined the binding relations between miR-454-3p and GADD45A and between miR-454-3p and lncRNA-DGCR5. The viability, apoptosis, migration, invasiveness and tube formation of HTR-8/SVneo cell were evaluated using cell counting kit (CCK)-8, Annexin-V/Propidium iodide staining, wound healing, transwell and tube formation assays, respectively. miR-454-3p was low-expressed in PE tissue, and upregulation of miR-454-3p increased viability and promoted migration, invasion and tube formation in HTR-8/SVneo cells while inhibiting apoptosis. Then, miR-454-3p was found to directly target GADD45A which was high-expressed in PE tissues. Overexpressing GADD45A decreased the viability and inhibited the migration, invasion and tube formation of HTR-8/SVneo cells while enhancing apoptosis, and it neutralized the effect of miR-454-3p upregulation. In turn, miR-454-3p upregulation reversed the effect of GADD45A overexpression. Meanwhile, miR-454-3p could also target lncRNA-DGCR5. Silencing lncRNA-DGCR5 increased miR-454-3p expression and cell viability and promoted migration, invasion and tube formation in HTR-8/SVneo cells while inhibiting apoptosis, and it counteracted the effect of miR-454-3p downregulation. As usual, miR-454-3p downregulation reversed the effect of lncRNA-DGCR5 silencing. To conclude, silencing lncRNA-DGCR5 increased viability, promoted migration, invasion and tube formation, and inhibited apoptosis in HTR-8/SVneo cells by rescuing the inhibition of GADD45A expression caused by miR-454-3p.

Gadd45α modulates aversive learning through post-transcriptional regulation of memory-related mRNAs.

Learning is essential for survival and is controlled by complex molecular mechanisms including regulation of newly synthesized mRNAs that are required to modify synaptic functions. Despite the well-known role of RNA-binding proteins (RBPs) in mRNA functionality, their detailed regulation during memory consolidation is poorly understood. This study focuses on the brain function of the RBP Gadd45α (growth arrest and DNA damage-inducible protein 45 alpha, encoded by the Gadd45a gene). Here, we find that hippocampal memory and long-term potentiation are strongly impaired in Gadd45a-deficient mice, a phenotype accompanied by reduced levels of memory-related mRNAs. The majority of the Gadd45α-regulated transcripts show unusually long 3' untranslated regions (3'UTRs) that are destabilized in Gadd45a-deficient mice via a transcription-independent mechanism, leading to reduced levels of the corresponding proteins in synaptosomes. Moreover, Gadd45α can bind specifically to these memory-related mRNAs. Our study reveals a new function for extended 3'UTRs in memory consolidation and identifies Gadd45α as a novel regulator of mRNA stability.

Neddylation promotes protein translocation between the cytoplasm and nucleus.

Neddylation is an ubiquitin-like modification of proteins that affects the activity, stability and protein-protein interaction of its substrates. Apart from its role as a promoter for Cullin ring E3 ligase to positively regulate the ubiquitylation process, other functional studies about neddylation are still lacking. In this study, we developed a system to explore the impact of neddylation on changes in the subcellular localization of proteins at the omics level. By applying a method combining subcellular protein extraction and immunoprecipitation-mass spectrometry (IP-MS), 81 proteins with a tendency to shuttle between the cytoplasm and nucleus due to different neddylation levels were obtained. Among the 81 candidates, transforming growth factor-ß (TGF-ß)-activated kinase 1 (TAK1) and growth arrest and DNA damage protein 45a (Gadd45a) were confirmed as novel substrates of Nedd8, and neddylation promotes TAK1 nuclear import as well as Gadd45a nuclear export.

Telomeric epigenetic response mediated by Gadd45a regulates stem cell aging and lifespan.

Progressive attrition of telomeres triggers DNA damage response (DDR) and limits the regenerative capacity of adult stem cells during mammalian aging. Intriguingly, telomere integrity is not only determined by telomere length but also by the epigenetic status of telomeric/sub-telomeric regions. However, the functional interplay between DDR induced by telomere shortening and epigenetic modifications in aging remains unclear. Here, we show that deletion of Gadd45a improves the maintenance and function of intestinal stem cells (ISCs) and prolongs lifespan of telomerase-deficient mice (G3Terc-/-). Mechanistically, Gadd45a facilitates the generation of a permissive chromatin state for DDR signaling by inducing base excision repair-dependent demethylation of CpG islands specifically at sub-telomeric regions of short telomeres. Deletion of Gadd45a promotes chromatin compaction in sub-telomeric regions and attenuates DDR initiation at short telomeres of G3Terc-/- ISCs. Treatment with a small molecule inhibitor of base excision repair reduces DDR and improves the maintenance and function of G3Terc-/- ISCs. Taken together, our study proposes a therapeutic approach to enhance stem cell function and prolong lifespan by targeting epigenetic modifiers.

Expression and prognostic significance of the P53-related DNA damage repair proteins checkpoint kinase 1 (CHK1) and growth arrest and DNA-damage-inducible 45 alpha (GADD45A) in human oral squamous cell carcinoma.

DNA damage repair is a key factor in the maintenance of cell genome stability, plays an important role in the regulation of tumour evolution, and can affect the prognosis of cancer patients. This study aimed to detect the protein expression of the DNA damage repair protein P53 and its upstream and downstream regulators, CHK1, GADD45A, and MDM2, in oral squamous cell carcinoma (OSCC), in order to analyse the association between the expression of these proteins and overall survival, and to assess their prognostic implications for OSCC patients. The expression of the above proteins was detected by immunohistochemistry in 80 human OSCC tissue samples and in non-cancerous tissue samples. Compared to that in the non-cancerous tissue, the expression of CHK1, GADD45A, and MDM2 in OSCC tissue was significantly increased. The protein expression of the tumour suppressor gene P53 was also increased. Patients with high CHK1 and MDM2 expression levels had a reduced survival time and a poor prognosis, whereas patients with high GADD45A expression levels had a good prognosis. Our results indicate that high CHK1 expression is an independent risk factor for poor OSCC prognosis, and that CHK1 may be a potential target for OSCC clinical treatment.

Insulin receptor substrate 1 gene expression is strongly up-regulated by HSPB8 silencing in U87 glioma cells.

Objective. The aim of the present investigation was to study the expression of genes encoding IRS1 (insulin receptor substrate 1) and some other functionally active proteins in U87 glioma cells under silencing of polyfunctional chaperone HSPB8 for evaluation of the possible significance of this protein in intergenic interactions.Methods. Silencing of HSPB8 mRNA was introduced by HSPB8 specific siRNA. The expression level of HSPB8, IRS1, HK2, GLO1, HOMER3, MYL9, NAMPT, PER2, PERP, GADD45A, and DEK genes was studied in U87 glioma cells by quantitative polymerase chain reaction.Results. It was shown that silencing of HSPB8 mRNA by specific to HSPB8 siRNA led to a strong down-regulation of this mRNA and significant modification of the expression of IRS1 and many other genes in glioma cells: strong up-regulated of HOMER3, GLO1, and PERP and down-regulated of MYL9, NAMPT, PER2, GADD45A, and DEK gene expressions. At the same time, no significant changes were detected in the expression of HK2 gene in glioma cells treated by siRNA, specific to HSPB8. Moreover, the silencing of HSPB8 mRNA enhanced the glioma cells proliferation rate.Conclusions. Results of this investigation demonstrated that silencing of HSPB8 mRNA affected the expression of IRS1 gene as well as many other genes encoding tumor growth related proteins. It is possible that the dysregulation of most of the studied genes in glioma cells after silencing of HSPB8 is reflected by a complex of intergenic interactions and that this polyfunctional chaperone is an important factor for the stability of genome function and regulatory mechanisms contributing to the tumorigenesis control.