Involvement of ATR-CHK1 pathway in fish megalocytivirus infection induced DNA-damage response in vitro

Increasing evidence has demonstrated that megalocytiviruses cause severe disease with high mortality in both freshwater and marine species. However, the molecular events employed in megalocytivirus infection in vitro still remained largely uncertain. Here, using an in vitro infection model of sea perch iridovirus (SPIV), we investigated the transcriptomic profiles of sea perch fry (SPF) cells upon SPIV infection, and elucidated the roles of crucial molecular events during infection using the specific inhibitors. Our data showed that almost all the differentially expressed genes (DEGs) associated with DNA-damage response (DDR), including DNA replication, mismatch repair, homologous recombination, nucleotide excision repair and Fanconi anemia (FA) pathway exhibited the up-regulation expression patterns during SPIV infection. As expected, DNA damage was detected in infected SPF cells, as evidenced by the DNA migration and the increased phosphorylation levels of H2AX along with the infection time. Furthermore, the key components of DDR, ataxia telangiectasia mutated and Rad3 related (ATR) and checkpoint kinase 1 (CHK1) kinases were elucidated to be essential for SPIV replication. Meanwhile, we also found that SPIV infection induced cell cycle arrest at G2/M phase, and 45 genes related to cell cycle pathway were up-regulated during infection. Inhibition of ATR activity induced cell cycle arrest of the infected cells at S phase, perhaps leading to the inhibitory effects on SPIV replication. Together, our data demonstrated for the first time that fish megalocytivirus induced DDR in vitro, and the ATR-CHK1 pathway exerted crucial roles in viral replication via regulating the cell cycle progression. These findings also provided new insights into the understanding of the interactions between fish megalocytivirus and host cells in vitro.