Abstract. 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. IntroductionUbiquitin-specific processing enzyme 22 (USP22) is a novel deubiquitinating enzyme that can cleave ubiquitin (Ub) from Ub-conjugated protein substrates (1). As the subunit of the human SAGA coactivator complex, USP22 is linked to the regulation of gene transcription by deubiquitinating histones H2A and H2B (2,3). In addition, USP22 deubiquitinates intracellular protein, including the shelterin protein telomeric repeat binding factor 1 (4), the histone deacetylase sirtuin 1 (5) and the far upstream element-binding protein 1 fructose-1,6-bisphosphatase 1 (4), and therefore performs an extensive physiological function. A murine study showed that USP22 also regulates embryonic stem cell differentiation (6). In humans, the USP22 gene is located on chromosome 17, consists of 14 exons, and is transcribed and produced broadly across various tissues (7). Of note, elevated levels of USP22 have been identified in numerous types of human cancer, including colorectal (8) lung (9) and breast cancer (10). USP22 has been indicated in tumorigenesis. Deletion of USP22 leads to the accumulation of cells in the G 1 phase of the cell cycle (2). For these reasons, USP22 is a putative cancer stem cell marker. Reducing the rate of USP22 expression may be a suitable target for cancer therapy (11). However, the mechanisms that lead to USP22 transcriptional activation, particularly in the human tumor cells, remain unknown.Previously, USP22 transcription was activated by mitogen stimulation or viral infection in normal T and B lymphocytes (12), suggesting the regulation of USP22 gene expression occurs mainly at the transcriptional level. However, the mechanism in which signal transduction pathways regulate USP22 transcription is unclear. It is well-known that activation of the mito...

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.