Molecular characterization and expression analysis of double‐stranded RNA‐dependent protein kinase (PKR) in Dabry’s sturgeon ( Acipenser dabryanus )

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Protein kinase RNA-activated (PKR) is an important component of the innate immune system induced by interferon. This antiviral protein senses a variety of stresses and pathogen-driven double-stranded RNAs (dsRNAs). In the present study, we cloned and characterized the PKR gene from Dabry's sturgeon (Acipenser dabryanus). Bioinformatics analysis revealed that the AdPKR gene comprises a coding sequence (CDS) of 1848 bp, encoding a 616 amino acids (aa) polypeptide. AdPKR shares high aa identity/similarity with proteins from other fish, ranging from 33.4%/51.8% to 87.6%/91.2%, and relatively low aa identity (13.9%) and similarity (26.8%) with human PKR. The AdPKR polypeptide has two dsRNA-binding motifs at the N-terminus and a conserved catalytic kinase domain at the C-terminus. The sturgeon PKR gene contains 17 exons split by 16 introns. Phylogenetic analysis clustered AdPKR together with its counterparts from other teleost fishes. Real-time fluorescene quantitative PCR (RT-qPCR) transcription profiles revealed highest AdPKR expression levels in brain, followed by middle kidney, skin, muscle and head kidney. AdPKR mRNA transcripts were significantly increased at 6 hr post-stimulation (hps) with polyinosinic:polycytidylic acid (poly I:C), remained high at 24 hps, then decreased to normal levels at 48 hps. These results indicate that AdPKR might play a vital role in antiviral immune responses.