Grass carp (Ctenopharyngodon idella) DYRK2 modulates cell apoptosis through phosphorylating p53

In mammals, DYRK2 increases p53 phosphorylation level by interacting with it and then promotes cell apoptosis. However, the function of fish DYRK2 has not yet been elucidated. In this paper, we cloned and identified the coding sequence (CDS) of a grass carp DYRK2 (CiDYRK2) which is 1773 bp in length and encodes 590 amino acids. SMART predictive analysis showed that CiDYRK2 possesses a serine/threonine kinase domain. Subsequently, we used the dsRNA analog polyinosinic-polycytidylic acid (poly (I:C) and Grass carp reovirus (GCRV) to stimulate grass carp and CIK cells for different times and found that CiDYRK2 mRNA was significantly up-regulated both in fish tissues and cells. To explore the function of CiDYRK2, we carried out overexpression and knockdown experiments of CiDYRK2 in CIK cells. Real-time quantitative PCR (Q-PCR), TdT-mediated dUTP nick end labeling (TUNEL) assay and flow cytometry were used to detect the ratio of BAX/BCL-2 mRNA, the number of TUNEL positive cells, the proportion of Annexin V-positive cells respectively. The results showed that CiDYRK2 significantly up-regulated BAX/Bcl-2 mRNA ratio and increased the number of TUNEL-positive cells, as well as the proportion of Annexin V-positive cells. On the contrary, knock-down of CiDYRK2 significantly down-regulated BAX/Bcl-2 mRNA ratio in the cells. Therefore, CiDYRK2 promoted cell apoptosis. To study the molecular mechanism by which CiDYRK2 promoting cell apoptosis, subcellular localization and immunoprecipitation experiments were used to study the relationship between grass carp DYRK2 and the pro-apoptotic protein p53. The results showed that CiDYRK2 and Cip53 were located and co-localized in the nucleus. Co-immunoprecipitation experiment also showed that CiDYRK2 and Cip53 can bind with each other. We further found that DYRK2 can increase the phosphorylation level of p53. In a word, our results showed that grass carp DYRK2 induces cell apoptosis by increasing the phosphorylation level of p53.