XBP1 and infection: Similarly, in HRTV-infected HEK 293 cells, an increase in phosphorylation level of eIF2a protein began to be detected at 48 h p.i., while a decrease in ATF6 p90 protein began to be detected at 24 h p.i. (Fig. 7D), and a weak increase in the spliced XBP1 mRNA was detected at 12 h p.i. (Fig. 7F), suggesting that infection of HRTV could also activate the three branches of the UPR.