Molecular and functional characterization of pigeon (Columba livia) tumor necrosis factor receptor-associated factor 3

Tumor necrosis factor receptor-associated factor 3 (TRAF3) plays a key antiviral role by promoting type I interferon production. We cloned the pigeon TRAF3 gene (PiTRAF3) according to its predicted mRNA sequence to investigate its function. The 1704-bp full-length open reading frame encodes a 567-amino acid protein. One Ring finger, two TRAF-type Zinc fingers, one Coiled coil, and one MATH domain were inferred. RT-PCR showed that PiTRAF3 was expressed in all tissues, with relatively weak expression in the heart and liver. In HEK293T cells, over-expression of wild-type, △Ring, △Zinc finger, and △Coiled coil PiTRAF3, but not a △MATH form, significantly increased IFN-β promoter activity. Zinc finger and Coiled coil domains were essential for NF-κB activation. In chicken HD11 cells, PiTRAF3 increased IFN-β promoter activity and four domains were all contributing. R848 stimulation of pigeon peripheral blood mononuclear cells and splenocytes significantly increased expression of PiTRAF3 and the inflammatory cytokine genes CCL5, IL-8, and IL-10. These data demonstrate TRAF3's innate immune function and improve understanding of its involvement in poultry antiviral defense.