Ctenopharyngodon idella p53 mediates between NF-κB and PKR at the transcriptional level.

p53, NF-κB and PKR are well-known to be involved in antiviral response. Although p53 has been reported in fish, its role in the regulation of NF-κB and PKR is not well understood. Here, we cloned and characterized the full length of cDNA sequence of grass carp (Ctenopharyngodon idella) p53 (Cip53) and its promoter sequence. The full length cDNA of Cip53 was 1879 bp with an ORF of 1116 bp encoding a polypeptide of 371 amino acids. Phylogenetic tree analysis revealed that Cip53 shares high homology with Dario rerio p53 (Drp53). Similar to those of Cip65 and CiPKR, the expression of Cip53 in CIK cells was significantly up-regulated after stimulation with poly I:C. To further understand the roles of fish p53 in the transcriptional control of NF-κB and PKR, Cip53 and Cip65 were expressed in E. coli BL21 and purified by affinity chromatography with the Ni-NTA His-Bind resin. In vitro, gel mobility shift assays demonstrated that the high affinity interaction between Cip65 and Cip53 promoter. Similarly, Cip53 bound to CiPKR promoter with high affinity. Dual-luciferase reporter assays showed that Cip65 activated Cip53 promoter and Cip53 activated CiPKR promoter, respectively. In addition, the role of p53 in p65-p53-PKR transcription pathway was explored. When Cip53 was knockdown in CIK cells, the mRNA levels of Cip65 and CiPKR were decreased. Taken together, p53 may play pivotal roles in transcription pathway of NF-κB and PKR in fish.