Silencing of CHD5 Gene by Promoter Methylation in Leukemia

Abstract

Chromodomain helicase DNA binding protein 5 (CHD5) was previously proposed to function as a potent tumor suppressor by acting as a master regulator of a tumor-suppressive network. CHD5 is down-regulated in several cancers, including leukemia and is responsible for tumor generation and progression. However, the mechanism of CHD5 down-regulation in leukemia is largely unknown. In this study, quantitative reverse-transcriptase polymerase chain reaction and western blotting analyses revealed that CHD5 was down-regulated in human leukemia cell lines and samples. Luciferase reporter assays showed that most of the baseline regulatory activity was localized from 500 to 200 bp upstream of the transcription start site. Bisulfite DNA sequencing of the identified regulatory element revealed that the CHD5 promoter was hypermethylated in human leukemia cells and samples. Thus, CHD5 expression was inversely correlated with promoter DNA methylation in these samples. Treatment with DNA methyltransferase inhibitor 5-aza-2′-deoxycytidine (DAC) activates CHD5 expression in human leukemia cell lines. In vitro luciferase reporter assays demonstrated that methylation of the CHD5 promoter repressed its promoter activity. Furthermore, a chromatin immunoprecipitation assay combined with qualitative PCR identified activating protein 2 (AP2) as a potential transcription factor involved in CHD5 expression and indicated that treatment with DAC increases the recruitment of AP2 to the CHD5 promoter. In vitro transcription-factor activity studies showed that AP2 over-expression was able to activate CHD5 promoter activity. Our findings indicate that repression of CHD5 gene expression in human leukemia is mediated in part by DNA methylation of its promoter.

Tumor suppressors in acute myeloid leukemia

“…In addition, CHD5 is frequently found to be silenced by promoter methylation in AML. Similar to its described role in other cancers, CHD5 controls cell proliferation and suppresses leukemogenesis in AML [67]. In pediatric AML patients, early EBF3 is repressed by promoter hypermethylation based on its role in apoptosis regulation, which renders also EBF3 tumor suppressor in AML [68].…”

Proteomic Studies for the Investigation of γ-Globin Induction by Decitabine in Human Primary Erythroid Progenitor Cultures

“…These findings suggest that decitabine promotes transcriptional termination and post-transcriptional processes. Decitabine also appears to regulate chromatin remodeling as can be observed by the up-regulation of SMARCD3, a subunit of SWI/SNF complex that promotes DNA-histone dissociation [55] and the downregulation of CHD5, a chromatin remodeling, helicase and DNA-binding protein which is activated by demethylation of its promoter [56]. A hypothetical pathway of the effects of decitabine treatment of thalassemic cultures is shown in Figure 2.…”

The Chromodomain Helicase DNA-Binding Chromatin Remodelers: Family Traits that Protect from and Promote Cancer

“…Loss of function CHD5 lesions including compromised expression, promoter hypermethylation, deletion and/or mutation have been reported in glioma (Bagchi et al 2007; Mulero-Navarro and Esteller 2008; Wang et al 2013), neuroblastoma (Fujita et al 2008; Garcia et al 2010; Koyama et al 2012; Li et al 2012), lung cancer (Zhao et al 2012), prostate cancer (Robbins et al 2011), breast cancer (Mulero-Navarro and Esteller 2008; Wu et al 2012), pancreatic adenocarcinoma (Hall et al 2014), gastric cancer (Wang et al 2009; Qu et al 2013), bladder cancer (Wu et al 2015), ovarian cancer (Gorringe et al 2008; Wong et al 2011), gallbladder carcinoma (Du et al 2013), colorectal cancer (Mulero-Navarro and Esteller 2008; Mokarram et al 2009; Cai et al 2012; Fatemi et al 2014), hepatocellular carcinoma (Zhao et al 2014; Fang et al 2015; Xie et al 2015) melanoma (Lang et al 2011), leukemia (Zhao et al 2014), and laryngeal squamous cell carcinoma (Wang et al 2011). …”