Heat Shock Factor 1(HSF1)as A Host Factor Against Influenza Replication

Background:Seasonal influenza is an acute viral infection that spreads around the world and is easily transmitted from person to person.The current clinical anti-flu drugs mainly target viral proteins.Because of the frequent appearance of influenza virus resistant strains,the research and efficacy of anti-flu drugs are limited.Therefore,the researchers proposed a host-targeted anti-flu strategy.The process of viral entering target cells and replication requires the assistance of a large number of host factors in the cells.High fever is a common symptom of influenza.In the case of high temperature,the body often causes heat shock response,and heat shock factor 1(HSF1)is the main host factor involved in heat shock response.Some researches reported that HSF1 is an important host factor that regulates transcription and various cellular functions to resist a variety of external stimuli,such as thermal,chemical,and viral infections.HSF1 not only functions in the heat shock response,but also has multiple roles in both aging and disease.Researchers have found that HSF1 is associated with HIV,dengue virus,and other RNA viruses.Therefore,we speculated that HSF1 might participate in the replication process of influenza A viruses by regulating various cellular functions.Objectives:In this project,we selected HSF1 as the research object,to explore the effect of HSF1 on the replication of influenza A virus,and further clarified the mechanism of HSF1 in viral infection.Our work could provide basis researches and ideas for finding new antiviral targets.Methods:1.CRISPR-Cas9 technology,high-speed flow cytometry technology and screening with puromycin were operated for the construction of KO-HSF1-A549 cells.2.Western blotting,qRT-PCR,plaque assay and indirect immunofluorescence assay were used to detect the regulation of HSF1 on influenza virus infection.3.Mini-replicon experiment and Time-of-addition experiment are used to detect the replication stage of influenza virus.Results:1.Phosphorylated HSF1 protein at Ser 326 was increased along with viral infection.However,the expression of HSF1 total protein and mRNA level did not change significantly.2.The expression of NP reduced in HSF1-deficient A549 cells compared with parental group and the release of progeny virus also decreased.After the cells are heat shocked,the progeny influenza virus release increases.3.The expression of influenza virus protein were reduced after KRIBB11 treatment in A549 cells and Beas-2B cells and the release of progeny viruses was also reduced.4.There-was a notable decrease occurring from 2-5 h KRIBB11-treated periods on the expression of NP.KRIBB11 also blocked the activity of vRNP to reduce the early synthesis of vRNA,cRNA and mRNA.5.HSF1 inhibitors reduced cellular autophagy caused by influenza virus and rapamycin,and also reduced the protein expression of autophagy-related gene ATG7.Conclusion:1.Influenza virus can activate HSF1 in cells.2.Endogenous HSF1 can regulate the infection of influenza virus.3.HSF1 inhibitors can inhibit the replication of influenza virus.4.HSF1 affects the early stages of influenza virus replication and affects vRNP expression,thus affecting the early synthesis of cRNA,vRNA and mRNA.5.HSF1 inhibitors can regulate the autophagy-related gene ATG7 to reduce cellular autophagy caused by influenza viruses,thereby inhibiting virus replication.