Molecular cloning and expression analysis of TRAF3 in chicken

Tumor necrosis factor receptor-associated factor 3 (TRAF3) is a crucial regulator that suppresses c-Jun N-terminal kinase and non-canonical nuclear factor-kB signaling, but facilitates type I interferon production. To determine TRAF3 function in innate immune responses among birds, particularly chicken, we cloned and characterized the chicken TRAF3 gene (chTRAF3) and detected its tissue expression profile in chicken. We also detected the differential expression of chTRAF3 and its downstream gene interferon-β (IFN-β) upon different stimuli in primary chicken embryo fibroblast cells. Two chTRAF3 gene products, chTRAF3-1 and chTRAF3-2, can be produced by alternative splicing. The full-length coding sequence of chTRAF3 (chTRAF3-1) was 1704 base pairs and encoded a protein of 567 amino acids with high identity to TRAF3 homologs from mammals and other birds. The deduced amino acid sequence showed typical characteristics of TRAFs, with a RING finger domain, 2 zf-TRAF motifs, and a MATH domain. Quantitative real-time polymerase chain reaction analysis revealed broad expression of chTRAF3 in all detected tissues, with abundant expression in the spleen, thymus, lung, and small intestine. Expression of chTRAF3 was significantly upregulated in a time- and concentration-dependent manner in chicken embryo fibroblast cells challenged with poly I:C or poly dA-dT. Furthermore, chTRAF3 and IFN-β mRNA expression from chicken embryo fibroblast cells challenged with Newcastle disease virus F48E9 suffered intense suppression compared with Newcastle disease virus Mukteswar infection. Our results indicate that chTRAF3 plays important roles in defending against both RNA and DNA virus infection.