PATZ1 Is a DNA Damage-Responsive Transcription Factor That Inhibits p53 Function

Abstract

e Insults to cellular health cause p53 protein accumulation, and loss of p53 function leads to tumorigenesis. Thus, p53 has to be tightly controlled. Here we report that the BTB/POZ domain transcription factor PATZ1 (MAZR), previously known for its transcriptional suppressor functions in T lymphocytes, is a crucial regulator of p53. The novel role of PATZ1 as an inhibitor of the p53 protein marks its gene as a proto-oncogene. PATZ1-deficient cells have reduced proliferative capacity, which we assessed by transcriptome sequencing (RNA-Seq) and real-time cell growth rate analysis. PATZ1 modifies the expression of p53 target genes associated with cell proliferation gene ontology terms. Moreover, PATZ1 regulates several genes involved in cellular adhesion and morphogenesis. Significantly, treatment with the DNA damage-inducing drug doxorubicin results in the loss of the PATZ1 transcription factor as p53 accumulates. We find that PATZ1 binds to p53 and inhibits p53-dependent transcription activation. We examine the mechanism of this functional inhibitory interaction and demonstrate that PATZ1 excludes p53 from DNA binding. This study documents PATZ1 as a novel player in the p53 pathway. Wild-type (WT) p53 is a stress-responsive, sequence-specific transcription factor that inhibits the cell cycle, promotes senescence, and, if the insult to cellular health is not resolved, induces apoptotic death (1). p53 mutations that allow cells to escape this death are the most common genetic event in human cancer (2). Alternative mechanisms of escape rely on the overexpression of MDM2 and MDMX, major negative regulators of p53 that keep p53 levels low under unstressed conditions through ubiquitination-mediated degradation (3). Moreover, many DNA tumor viruses encode proteins that can inactivate p53 (2). However, the list of p53 regulators is far from complete. Various stress conditions result in the upregulation of p53, controlled by feedback loops, posttranslational modifications, and epigenetic changes. In the present study, we aimed to find new players that modify p53 function.p53 is composed of an N-terminal transactivation domain (through which it interacts with MDM2), a proline-rich domain, central DNA binding and tetramerization domains, and a C-terminal regulatory domain. p53 binds response elements (REs) in nuclear DNA, which results in stress-induced changes (either upor downregulation) in gene expression. Tetrameric p53 binds REs that are composed of two half-sites, each with a consensus of RR RCWWGYYY, separated by 0 to 21 bases (where R is a purine, Y is a pyrimidine, and W is either an A or T) (4). p53 REs can be subcategorized as those that respond to low levels of wild-type p53, those that respond to stabilized p53 after stress, and those that respond to p53 with mutations in its DNA binding domain. A recent study found 160 p53 REs controlling 129 genes in the human genome (5). Another study using chromatin immunoprecipitation (ChIP) with paired-end ditag (PET) sequencing identified 542 functional p53 binding sites...

The Tumor Suppressive Role of PATZ1 in Thyroid Cancer: A Matter of Epithelial-Mesenchymal Transition

“…Consistent with the ability of PATZ1 to interact with p53 and regulate transcription of p53 target genes [10,13], we next showed that in PATZ1-expressing cells the EMT and cell migration gene program, activated by EGF and negatively regulated by p53, was deregulated. In more details, PATZ1 binds the promoter regions of three genes, EpCam, RhoE and Caldesmon, involved in EMT, cellular migration and invasion, respectively, modulating their transcriptional changes associated with EGF stimulation (Figure 1).…”

“…Consistently, silencing of PATZ1 expression in a p53-null osteosarcoma cell line enhanced its sensitivity to the proapoptotic chemotherapeutic agent 5-fluorouracil (5FU), while Patz1-/-mouse embryonic fibroblasts show a decreased number of apoptotic cells, either spontaneous or induced by 5FU treatment, compared with wild-type controls [10]. However, in a colon cancer cell line, even in the presence of a wild-type p53, PATZ1 has been shown to inhibit p53 function [13], supporting the concept that PATZ1 may have opposite roles on p53 in different tumors. In this context, our recent studies show that PATZ1 acts as a tumor suppressor in thyroid cancer via targeting p53-dependent genes involved in EMT and cell migration [17].…”

“…It has been recently indicated as a "stemness factor" [11] and shown to play a critical role in reprogramming somatic cells into pluripotent stem cells [12]. PATZ1 expression is regulated by DNA damage [13] and appears deregulated in different human cancers, suggesting a cancer-related role [14][15][16][17], which appears oncogenic or anti-oncogenic depending on the tumor type and likely on the presence/absence of a wild-type p53 protein with which it interacts [10,13]. Consistently, silencing of PATZ1 expression in a p53-null osteosarcoma cell line enhanced its sensitivity to the proapoptotic chemotherapeutic agent 5-fluorouracil (5FU), while Patz1-/-mouse embryonic fibroblasts show a decreased number of apoptotic cells, either spontaneous or induced by 5FU treatment, compared with wild-type controls [10].…”

Genetic alterations in uncommon low-grade neuroepithelial tumors: BRAF, FGFR1, and MYB mutations occur at high frequency and align with morphology

“…A similar fusion involving these two genes has been described once before in an undifferentiated sarcoma that presented in the chest wall of a teenager [33]. PATZ1 is a BTB-ZF transcription factor that inhibits the ability of p53 to bind to its response elements and is involved in keeping embryonic stem cells in an undifferentiated state [28,37]. Rearrangement of EWSR1 is found in intracranial Ewing sarcomas that involve the inner table of the skull and extraosseous meningeal ‘peripheral’ primitive neuroectodermal tumors [35,52].…”

Structural analysis of the PATZ1 BTB domain homodimer

“…PATZ1 also negatively regulates induced pluripotent stem-cell (iPSC) generation (Ow et al, 2014;Ma et al, 2014). This function may be related to its interaction with the p53 tumour suppressor, as demonstrated by various studies (Valentino, Palmieri, Vitiello, Pierantoni et al, 2013;Keskin et al, 2015;Chiappetta et al, 2015).…”