Characterization of chicken melanoma differentiation-associated gene 5 (MDA5) from alternative translation initiation.

The present study was undertaken to identify and characterize chicken melanoma differentiation-associated gene 5 (MDA5) from alternative translation initiation. The alternatively translated chicken MDA5 had an open reading frame of 3309 base pairs, shorter than the predicted chicken MDA5 sequence by 549 base pairs and longer than the recently published chicken MDA5 (GU570144) by 303 base pairs. The domain architecture was conserved among MDA5 molecules from various vertebrates. The alternatively translated chicken MDA5 shared high genetic identity to zebrafinch MDA5, but not to fish or mammalian MDA5. Various concentrations of chicken MDA5 transcripts were detected in different chicken tissues, with the highest concentration found in the intestine (1.4×10(10)copy/mg tissue). Chicken interferon (IFN-β) expression was dependent on the dose of pCDNA3.1-MDA5-long transfection in DF1 cells without double-stranded RNA stimulation. DF1 cells transfected with polyinosinic-polycytidylic acid (poly(I:C)) had significantly (p<0.05) increased fold changes in chicken MDA5 and IFN-β mRNA expression as compared to those in the controls. DF1 cells incubated with poly(I:C) did not have significant (p>0.05) changes in mRNA expression of chicken MDA5 and IFN-β. Chicken MDA5 mRNA level did not change significantly (p>0.05) in DF1 cells treated with imiquimod or bacterial DNA. The results indicate that although chicken MDA5 is phylogenetically different from mammalian MDA5, the domain architecture remains conserved. Chicken MDA5 can be detected in various tissues and functions to signal the activation of chicken IFN-β when overexpressing or being stimulated by poly(I:C).