Cloning and characterization of the human USP22 gene promoter

Transcription factor AP2 enhances malignancy of non-small cell lung cancer through upregulation of USP22 gene expression

BACKGROUND

Ubiquitin-specific protease 22 (USP22), a putative cancer stem cell marker, is frequently upregulated in cancers, and USP22 overexpression is associated with aggressive growth, metastasis, and therapy resistance in various human cancers including lung cancer. However, USP22 gene amplification seldom occurs, and the mechanism underlying USP22 upregulation in human cancers remains largely unknown.

METHODS

A luciferase reporter driven by a promoter region of USP22 gene was selectively constructed to screen against a customized siRNA library targeting 89 selected transcription factors to identify potential transcription factors (TFs) that regulate USP22 expression in human non-small cell lung cancers (NSCLC). Association of identified TFs with USP22 and potential role of the TFs were validated and explored in NSCLC by biological assays and immunohistochemistry analysis.

RESULTS

Luciferase reporter assays revealed that SP1 and activating transcription factor 3 (ATF3) inhibit USP22 transcription, while transcription factor AP-2 Alpha/Beta (TFAP2A/2B) and c-Myc promote USP22 transcription. Binding site-directed mutagenesis and chromosome immunoprecipitation (ChIP) assays validated AP2α and AP2β are novel TFs of USP22. Furthermore, overexpression of AP2A and AP2B significantly upregulates USP22 expression, and its target: Cyclin D1, concurrently enhances the proliferation, migration, and invasion of NSCLC A549 and H1299 cells in a partially USP22-dependent manner. Moreover, AP2 protein level correlated with USP22 protein in human NSCLC tissues.

CONCLUSION

Our findings indicate AP2α and AP2β are important transcription factors driving USP22 gene expression to promote the progression of NSCLC, and further support USP22 as a potential biomarker and therapeutic target for lung cancer. Video Abstract.

Coenzyme Q10 deficiency can be expected to compromise Sirt1 activity

For reasons that remain unclear, endogenous synthesis and tissue levels of coenzyme Q10 (CoQ10) tend to decline with increasing age in at least some tissues. When CoQ10 levels are sufficiently low, this compromises the efficiency of the mitochondrial electron transport chain, such that production of superoxide by site 2 increases and the rate of adenosine triphosphate production declines. Moreover, CoQ10 deficiency can be expected to decrease activities of Sirt1 and Sirt3 deacetylases, believed to be key determinants of health span. Reduction of the cytoplasmic and mitochondrial NAD⁺/NADH ratio consequent to CoQ10 deficit can be expected to decrease the activity of these deacetylases by lessening availability of their obligate substrate NAD⁺. The increased oxidant production induced by CoQ10 deficiency can decrease the stability of Sirt1 protein by complementary mechanisms. And CoQ10 deficiency has also been found to lower mRNA expression of Sirt1. An analysis of the roles of Sirt1/Sirt3 in modulation of cellular function helps to rationalise clinical benefits of CoQ10 supplementation reported in heart failure, hypertension, non-alcoholic fatty liver disease, metabolic syndrome and periodontal disease. Hence, correction of CoQ10 deficiency joins a growing list of measures that have potential for amplifying health protective Sirt1/Sirt3 activities.

Maintaining Effective Beta Cell Function in the Face of Metabolic Syndrome-Associated Glucolipotoxicity-Nutraceutical Options

In people with metabolic syndrome, episodic exposure of pancreatic beta cells to elevated levels of both glucose and free fatty acids (FFAs)-or glucolipotoxicity-can induce a loss of glucose-stimulated insulin secretion (GSIS). This in turn can lead to a chronic state of glucolipotoxicity and a sustained loss of GSIS, ushering in type 2 diabetes. Loss of GSIS reflects a decline in beta cell glucokinase (GK) expression associated with decreased nuclear levels of the pancreatic and duodenal homeobox 1 (PDX1) factor that drives its transcription, along with that of Glut2 and insulin. Glucolipotoxicity-induced production of reactive oxygen species (ROS), stemming from both mitochondria and the NOX2 isoform of NADPH oxidase, drives an increase in c-Jun N-terminal kinase (JNK) activity that promotes nuclear export of PDX1, and impairs autocrine insulin signaling; the latter effect decreases PDX1 expression at the transcriptional level and up-regulates beta cell apoptosis. Conversely, the incretin hormone glucagon-like peptide-1 (GLP-1) promotes nuclear import of PDX1 via cAMP signaling. Nutraceuticals that quell an increase in beta cell ROS production, that amplify or mimic autocrine insulin signaling, or that boost GLP-1 production, should help to maintain GSIS and suppress beta cell apoptosis in the face of glucolipotoxicity, postponing or preventing onset of type 2 diabetes. Nutraceuticals with potential in this regard include the following: phycocyanobilin-an inhibitor of NOX2; agents promoting mitophagy and mitochondrial biogenesis, such as ferulic acid, lipoic acid, melatonin, berberine, and astaxanthin; myo-inositol and high-dose biotin, which promote phosphatidylinositol 3-kinase (PI3K)/Akt activation; and prebiotics/probiotics capable of boosting GLP-1 secretion. Complex supplements or functional foods providing a selection of these agents might be useful for diabetes prevention.

ZRANB1 enhances stem-cell-like features and accelerates tumor progression by regulating Sox9-mediated USP22/Wnt/β-catenin pathway in colorectal cancer

The pathogenesis of colorectal cancer (CRC) is a multistep process characterized by the accumulation of gene mutations and epigenetic alterations. Tumor necrosis factor receptor-associated factor-binding protein domain (ZRANB1) is a deubiquitinase that mediates tumor growth and metastasis by deubiquitinating target proteins. In this study, we examined the regulatory effects of ZRANB1 on the maintenance of cancer stem cell (CSC) properties and tumor growth in CRC. Human CRC tissue samples and matched normal tissues were collected for the analysis of ZRANB1 expression. ZRANB1 was upregulated in CRC human tissues and cell lines, and its expression was positively correlated with advanced tumor stage and poor survival of CRC patients. The overexpression of ZRANB1 also induced the expression of CSC markers in CRC cells. Then, a xenograft model was established by inoculating BALB/c mice with CRC cells. The upregulation of ZRANB1 promoted tumorigenesis in vivo. Sox9 is a transcription factor that acts as an oncogene in human cancers. ZRANB1 increased the stability of Sox9 in CRC cells by decelerating its ubiquitination. Further analysis revealed that Sox9 regulated the transcription activity of USP22 by binding to its promoter. Moreover, ZRANB1 enhances stem-cell-like features of CRC cells and activated the Wnt/β-catenin pathway through USP22. Our results highlighted the role of ZRANB1 as a molecular target for CRC treatment, which may contribute to the development of novel therapies with better efficacy.

Ubiquitin-specific peptidase 22 in cancer

Recently, many studies have shown that deubiquitination modification of proteins is of great significance in major physiological processes such as cell proliferation, apoptosis, and differentiation. The ubiquitin-specific peptidase (USP) family is one of the most numerous and structurally diverse of the deubiquitinates known to date. USP22, an important member of the USP family, has been found to be closely associated with tumor cell cycle regulation, stemness maintenance, invasion and metastasis, chemoresistance, and immune regulation. We focus on recent advances regarding USP22's function in cancer and discuss the prospect of USP22 in this review.

USP22 promotes melanoma and BRAF inhibitor resistance via YAP stabilization

Yes-associated protein (YAP) is a conserved transcriptional coactivator that plays key roles in controlling organ size, tumorigenesis and drug resistance. Emerging evidence shows that YAP is overexpressed and associated with resistance to BRAF inhibitor treatment in melanoma. However, the mechanism accounting for YAP-overexpression in melanoma is largely unknown. The present study characterized ubiquitin-specific peptidase 22 (USP22) as a deubiquitinase controlling YAP abundance and biological functions in melanoma. Using western blotting and immunohistochemical staining, it was found that the expression of USP22 and YAP was associated in melanoma cell lines and patient samples. Moreover, USP22 interacted with and deubiquitinated YAP to prevent YAP turnover. Depletion of USP22 decreased YAP expression, which in turn suppressed cell proliferation and tumorigenesis. Furthermore, overexpression of USP22 conferred vemurafenib resistance in a YAP-dependent manner. Overall, the present study revealed the important role of the USP22/YAP axis in melanoma and BRAF inhibitor resistance, and provides a rationale to target USP22/YAP for melanoma treatment.

Deubiquitination in prostate cancer progression: role of USP22

Prostate cancer (PCa) is the leading cause of cancer death in men. With more therapeutic modalities available, the overall survival in PCa has increased significantly in recent years. Patients with relapses after advanced secondgeneration anti-androgen therapy however, often show poor disease prognosis. This group of patients often die from cancer-related complicacies. Multiple approaches have been taken to understand disease recurrence and to correlate the gene expression profile. In one such study, an 11-gene signature was identified to be associated with PCa recurrence and poor survival. Amongst them, a specific deubiquitinase called ubiquitin-specific peptidase 22 (USP22) was selectively and progressively overexpressed with PCa progression. Subsequently, it was shown to regulate androgen receptors and Myc, the two most important regulators of PCa progression. Furthermore, USP22 has been shown to be associated with the development of therapy resistant PCa. Inhibiting USP22 was also found to be therapeutically advantageous, especially in clinically challenging and advanced PCa. This review provides an update of USP22 related functions and challenges associated with PCa research and explains why targeting this axis is beneficial for PCa relapse cases.

Pirarubicin reduces USP22 expression by inhibiting CREB-1 phosphorylation in HeLa cells

The expression of ubiquitin specific peptidase 22 (USP22) is upregulated in several types of cancer, and has been implicated in tumorigenesis. Pirarubicin (THP), an anthracycline antineoplastic drug, can induce apoptosis of several types of cancer cells. However, the molecular mechanisms underlying the action of THP remain to be elucidated. In the current study, treatment with THP induced HeLa cell apoptosis and decreased USP22 expression in a dose- and time-dependent manner. THP reduced the USP22 promoter-regulated luciferase activity, regardless of the mutation of transcriptional activator MYB or E3 ubiquitin-protein ligase SP1 binding sequences; however, this effect was abrogated by the mutation of cyclic AMP-responsive element-binding protein (CREB) binding sequence in HeLa cells. Furthermore, the inhibition on the USP22 promoter activity by THP was not affected by overexpression of CREB-1 in HeLa cells. Additionally, treatment with THP significantly decreased the phosphorylation of CREB-1 at ser133 in HeLa cells. Quantitative chromatin immunoprecipitation assay revealed that THP significantly inhibited the binding of CREB-1 to the USP22 promoter in HeLa cells. The present study demonstrated that THP decreased USP22 expression and promoted HeLa cell apoptosis partially by inhibiting the phosphorylation of CREB-1. The current results may provide novel insights into the molecular mechanisms underlying the pharmacological effect of THP on cancer cell apoptosis.

Ubiquitin-specific peptidase 22 functions and its involvement in disease

Deubiquitylases remove ubiquitin moieties from different substrates to regulate protein activity and cell homeostasis. Since this posttranslational modification plays a role in several different cellular functions, its deregulation has been associated with different pathologies. Aberrant expression of the Ubiquitin-Specific Peptidase 22 (USP22) has been associated with poor cancer prognosis and neurological disorders. However, little is known about USP22 role in these pathologies or in normal physiology. This review summarizes the current knowledge about USP22 function from yeast to human and provides an overview of the possible mechanisms by which USP22 is emerging as a potential oncogene.

p38 mitogen-activated protein kinase inhibits USP22 transcription in HeLa cells

Elevated expression of ubiquitin-specific processing enzyme 22 (USP22) was identified in multiple types of human cancers, and was correlated with tumorigenesis and progression. Despite an increase in the numbers of studies in the physiological function of USP22, little is known regarding the regulation of its expression. The 5' flanking sequence of the USP22 gene was recently characterized. In the present study, USP22 transcription was regulated by p38 mitogen-activated protein kinase (MAPK). Treatment of human cervical carcinoma (HeLa) cells with SB203580, an inhibitor of p38 MAPK, enhanced basal USP22 promoter activity and mRNA abundance. Transfection of MAPK kinase 6 (MKK6), an upstream activator of p38 MAPK, resulted in a 40% decrease in USP22 mRNA, while the dominant negative MKK6 increased the transcription level of the USP22, similar to SB203580. Dual luciferase report assays showed that mutations of the Sp1 binding site ahead of the transcription start site abolished the promoting effect of the USP22 promoter by SB203580. Cisplatin, the activator of p38 MAPK, also suppressed USP22 expression. This suppression was blocked by SB203580. In conclusion, p38 MAPK acts as an upstream negative regulator of USP22 transcription in HeLa cells.

USP22 transcriptional activity is negatively regulated by the histone deacetylase inhibitor trichostatin A

The ubiquitin‑specific protease 22 (USP22) gene is overexpressed in the majority of types of cancer cells, and has been implicated in tumorigenesis. However, the mechanisms that regulate its expression remain unclear. The results of the present study demonstrated that the expression of USP22 is negatively regulated by trichostatin A (TSA), a classical histone deacetylase inhibitor. Furthermore, TSA was revealed to interfere with the binding of RNA polymerase II to the USP22 promoter, directly suppressing its transcription. In addition, the overexpression of USP22 was observed to attenuate TSA‑induced apoptosis in HeLa cells. To the best of our knowledge, these results provide the first insight into the regulation of the USP22 gene by antitumor drugs and into the mechanisms underlying the anticancer activity of TSA.