Mechanisms Of Histone H3 Acetylation In BoHV-1 Infection

Bovine herpesvirus type 1(BoHV-1)is a double-stranded DNA virus that include three serotypes:BoHV-I.1,BoHV-1.2a and BoHV-1.2b.BoHV-1 is the primary infection of infectious bovine rhinotracheitis(IBR)in the cattle.Then,BoHV-1 reaches trigeminal ganglion and travels to the conjunctiva via axonal transport,and establishes latency.It was reported that during bovine herpesvirus 1(BoHV-1)productive infection in cell cultures,partial of intranuclear viral DNA is present in nucleosomes,and viral protein VP22 associates with decreasing histone H4 acetylation,indicating the involvement of histone H4 acetylation in virus replication.Except H4,the role of H3,as another Histones with highly conserved sequences,in viral infection still worth of further exploration.In this study,we demonstrated that BoHV-1 infection at the late stage(at 24 h after infection)dramatically decreased histone H3 acetylation[at residues K9(H3K9ac)and K18(H3K18ac)],which consist with the result that the expression of HATs,such as CBP/p300,GCN5L2 and PCAF,is significantly reduced by viral infection.HATs activator CTPB increased the viral replication while HATs inhibitor AA decreased,and AA could reverse the decreased expression of H3K9ac caused by virus.Interesting,AA also effected the IE gene expression and decreased the expression of VP16,it shows that BoHV-1 infection may take advantage of histone acetylation for efficient replication.There are three pathways to control protein degradation in eukaryotic cells:ubiquitin-proteasome,lysosome and autophagy.This study demonstrated GCN5L2 was ubiquitinated after infection by IP assay,but H3K9ac was not,combining this result that the treatment of ubiquitin-proteasome inhibitor MG 132 reversed the depletion of both H3K9ac and H3K18ac attributed to virus.This result indicated that virus infection might target GCN5L2 for ubiquitin-mediated degradation,which would partially account for the depletion of acetylated histone H3;Lysosome inhibitor NH4Cl treatment did not show any effect;In this study,we found that the autophagy-related marker proteins including ATG5、LC3-Ⅰ、LC3-Ⅱ and Beclin-l were significantly reduced at the later stage of viral infection in a context of both with and without serum.Using inhibitors targeting different stages of autophagy formation,we discovered that 3-MA,an early stage autophagy inhibitor had no effects on virus replication,but BAF a later stage autophagy inhibitor could reduce virus replication.In addition,the decrease of ATG5,LC3-Ⅱ and Beclin一lcould be rescued by BAF treatment.We speculated that BoHV-1 infection needs the fundamentally autophagy formation and autophagy may be inhibited in the late stage of virus infection to maintain the survival of the virus itself.Although the treatment by HATs inhibitor AA could minorly reversed the decreased expression of ATG5,LC3-Ⅱ and Beclin-1 and HDAC inhibitor had no effects,we suggested that HATs play a role in the reduction of autophagic proteins by virus.In summary,this study was based on the reduction of H3 and its acetylation in MDBK cells infected with BoHV-1,the reduction mechanism of H3 and its acetylation in MDBK cells infected with BoHV-1 was preliminarily constructed from the four directions:enzymatic hydrolysis and three intracellular degradation pathways.