Small Molecule Compound JQ1 Promotes Adenovirus Replication And Its Infection Mechanism Research

Gene therapy delivers some specific nucleic acid into cell by using a naked plasmid,virus or other microorganism as a vector and to transcripts or translates for therapeutic purposes.Specific and efficient transduction of genetic nucleic acid into target cells is one of the most important obstacles in gene therapy.As a non-cellular organism,virus must complete its life cycle by infecting host cells and using the substances and energy in the host cells.Therefore,in the early stage of gene therapy,recombinant viruses are mainly used to transfer nucleic acid sequences into cells.The most used viruses include adenovirus,adeno-associated virus,retrovirus,and herpes virus.Their advantage is that they have relatively simple structure,small genome,and strong evolutionary plasticity,etc.Adenovirus is not carcinogenic,easy to prepare,and has the advantages of high transfection efficiency and wide tissue selectivity,it is the most widely used carrier in clinical research of gene therapy.The main disadvantage of adenovirus used in gene therapy vectors is that adenovirus is highly immunogenic and easily causes strong inflammatory reactions.In addition,since most adults are infected with adenovirus,neutralizing antibodies present in the body reduce transfection efficiency.Therefore,how to improve the transfection efficiency and reduce the host's immune response to the virus is a key issue for the successful use of adenoviral vectors for clinical treatment.Adenovirus-2 and-5(Ad2,Ad5)mainly use Coxsackievirus adenovirus receptor(CAR)to adhere to susceptible cells,and then activate cell invasion by binding to the integrin by the pento base protein.Adenovirus infection is regulated by host cytokines.Recent studies have reported that histone deacetylation inhibitors can increase the efficiency of adenovirus infection.The histone deacetylation process first recognizes the bromodomain(BD)family protein BRD4(Bromodomain-containing protein 4)and the like,causing specific residues to be deacetylated.Studies have found that BRD4 plays a role in the process of infecting cells with multiple viruses.This article aims to investigate the role of histone acetylated "Reader" protein BRD4 in adenovirus infection.This paper found that BRD4 small molecule inhibitor JQ1 can promote adenovirus infection.Further studies found that JQ1 can competitively bind to BRD4,so that BRD4 binding to genomic protein acetylated lysine residues is dissociated from the chromosome.Free BRD4 recruits and activates a positive transcription elongation factor(P-TEFb)through the C-terminal functional domain to form a transcriptionally active complex,which increases viral gene expression and promotes viral infection.CDK9 is a component of P-TEFb,and knockdown of BRD4 and CDK9 small molecule inhibitors can alleviate the promotion of adenovirus infection by JQ1.Replication-type viruses are mainly used in gene therapy,and the El A protein deleted by such viruses plays a key role in gene expression.In investigating the application of JQ1 in gene therapy for replication-deletion virus,we selected the E1A gene-deficient virus Ad5-EGFP as the research object.The study found that JQ1 can increase the expression of heterologous protein of replication-deficient virus Ad5?EGFP in epithelial cell A549 or lymphocyte Jurkat T.This indicates that JQ1 can increase the gene expression of the replication-deletion virus in a cell-free manner.In the mouse allogeneic tumor model experiment,P388D1 tumor infected with the same dose of replication-deficient virus vector in vitro was injected into the peritoneal cavity of mice,and treated with different concentrations of JQ1 or solvent control,it was found that JQ1 dose-dependently increased intra-abdominal adenovirus heterologous Gene expression.This study demonstrates that JQ1 promotes adenoviral gene expression,thereby promoting adenoviral infection and exploring its molecular mechanisms.In the field of tumor therapeutic applications,it was found that JQ1 can promote gene expression of replication-deficient virus in mouse tumor cells in vivo.It is suggested that when using the replication-deficient virus to treat tumors,JQ1 can regulate the expression of the target gene and enhance the therapeutic effect of the tumor.Adenovirus can infect a variety of cells and tissues,especially non-dividing cells,and efficiently express the delivered gene.So it becomes one of the most widely used viral vectors in gene therapy.However,adenoviral vector may initiate the host immune response easily and then be cleared,resulting in a short expression time of the target gene.Therefore,measures to reduce the immunogenicity of the adenovirus or improve the expression efficiency of the adenovirus can increase the gene therapy effect.We found that the small molecule inhibitor JQ1 of the BET protein family promotes adenovirus infection.In fact,JQ1 does not alter the phosphorylation or acetylation of intracellular histones,but by competitively binding to BRD4,dissociates the bound BRD4 from the chromosome and promotes the formation of a transcriptional complex between BRD4 and P-TEFb.This complex can increase the expression of adenovirus genes and promote adenovirus infection.Further studies have found that knockdown of BRD4 and the inhibitors of CDK9(functional subunit of P-TEFb)can offset the promotion of adenovirus infection by JQ1.In the application study of tumor therapy,we found that JQ1 can increase the expression of heterologous gene delivered by replication-deficient adenovirus(Ad5-EGFP)in mouse tumor model,suggesting that we can regulate the expression of delivered gene through JQ1 and enhance the therapeutic effect of gene therapy when adenovirus is used to treat tumor.