Role of the Bombyx mori nucleopolyhedrovirus LEF3 acetylation on viral replication

Late expression factor 3 (LEF3) is a single-stranded DNA binding protein of Bombyx mori nucleopolyhedrovirus (BmNPV) with multiple functions. It is an essential factor for viral DNA replication and plays an important regulatory role during BmNPV infection. Our recent quantitative analysis of protein acetylome revealed for the first time that LEF3 can be acetylated at four lysine residues during the viral infection, but the underlying mechanism is unknown. Among the modification sites, two of them (K18 and K27) are located in the conserved nuclear localization sequence region. The acetylation level for K18 especially was up-regulated approximately 7.4 times after 36 h of post-infection. To understand the regulatory function of this modification, site-direct mutagenesis for acetylated mimic (K18Q) or deacetylated mimic (K18R) mutants was performed on LEF3. The fluorescence analysis results showed that the replication capacity of the virus was significantly reduced after K18 acetylation. Meanwhile, co-localization analysis revealed that acetylation at K18 caused LEF3 to lose its nuclear targeting ability and affected the interaction between LEF3 and P143, retaining P143 in the cytoplasm. And further Yeast two-hybrid analysis results also confirmed that the acetylation at K18 did affect the interaction between LEF3 and P143. In conclusion, the acetylation of LEF3 at K18 might act as one of the antiviral strategies for silkworm host by affecting nuclear localization of LEF3, interaction with P143, and then blocking viral replication.