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• The cDNA sequence of DDX43 was identified from tilapia (Oreochromis niloticus). • Expressions of DDX43 mRNAs were altered after Streptococcus agalactiae , LPS, and poly I:C stimulation. • The overexpression of OnDDX43 could significantly upregulate IFN-β activity in 293 T cells. • OnDDX43 interacted with both IPS-1 and TRIF. DDX43 is one of the members of the DExD/H-box protein family, and emerging data suggest that it may play an important role in antiviral immunity across mammals. However, little is known about DDX43 in the fish immune response. In this study, we isolated the cDNA sequence of ddx43 in Nile tilapia (Oreochromis niloticus). The ddx43 gene was 2338 bp in length, contained an open reading frame (ORF) of 2064 bp and encoded a polypeptide of 687 amino acids. The predicted protein of On DDX43 has three conserved domains, including the RNA binding domain KH, DEAD-like helicase superfamily DEXDc and C-terminal HELICc domain. In healthy Nile tilapia, the Onddx43 transcript was broadly expressed in all examined tissues, with the highest expression levels in the muscle and brain and the lowest in the liver. After challenge with Streptococcus agalactiae , lipopolysaccharides (LPS) and polyinosinic polycytidylic acid (Poly I:C), the expression level of Onddx43 mRNA was upregulated or downregulated in all of the tissues tested. Overexpression of On DDX43 in 293 T cells showed that it has a positive regulatory effect on IFN-β. The subcellular localization showed that On DDX43 was expressed in the cytoplasm. We performed further pull-down assays and found that On DDX43 interacted with both interferon-β promoter stimulator1 (IPS-1) and TIR domain-containing adaptor inducing interferon-β (TRIF). [ABSTRACT FROM AUTHOR]

Abstract: DEAD box polypeptide 43 (DDX43), a cancer/testis antigen (CTA), has been found to be overexpressed in various solid tumors and some hematologic malignancies. In the present work hypomethylation of the DDX43 gene was detected in 15% (32/214) of primary acute myeloid leukemia (AML) using real-time quantitative methylation-specific PCR (RQ-MSP). The level of DDX43 expression was correlated with DDX43 hypomethylation (R =0.277, P =0.014). Moreover, bisulfite sequencing confirmed the significant correlation between the methylation density and the level of DDX43 hypomethylation. Additionally, restoration of DDX43 expression in the K562 cell line by 5-aza-2′-deoxycytidine treatment confirmed a direct contribution of methylation in regulating the DDX43 gene. DDX43 hypomethylation was observed more frequently in favorable group (21.4%) and intermediate group (15.8%) than in poor group (0%) (P =0.009). AML patients with DDX43 hypomethylation had a better overall survival (median not obtained) than those with DDX43 methylation (median 8 months, 95% confidence interval 5.6–10.4 months) (P =0.014). In summary, the DDX43 gene is activated by promoter hypomethylation and DDX43 hypomethylation may be a favorable prognostic factor in AML. [Copyright &y& Elsevier]