Molecular cloning and functional characterization of porcine DNA-dependent activator of IFN-regulatory factors (DAI)

The DNA-dependent activator of IFN-regulatory factors (DAI) is a recently identified DNA sensor for intracellular DNA that triggers a signal for the production of type I IFN. Here we report the cloning and characterization of porcine DAI (poDAI). The full-length of poDAI encodes 439 amino acids, contains two N-terminal DNA-binding domains and shows similarity to mouse, rat, dog, monkey, human, horse and cattle counterparts ranging from 44% to 67%. poDAI mRNA expression was mainly detected in spleen, lung, kidney and small intestine. Over-expression of poDAI activated transcription factors IRF3 and NF-κB and induced IFN-β in different porcine cell lines, but to varying degrees. Deletion mutant analysis revealed that both the DNA-binding domains and the C-terminus are required for full activation of IFN-β. siRNA targeting poDAI significantly decreased poly(dAT:dAT)- or Pseudorabies virus (PRV)-induced IFN-β activation. These results indicate that DAI is an important immuno-regulator of the porcine innate immune system.