Autographa californica multiple nucleopolyhedrovirus LEF-2 is a capsid protein required for amplification but not initiation of viral DNA replication.
The late expression factor 2 gene (lef-2) of baculovirus Autographa californica multiple nucleopolyhedrovirus (AcMNPV) has been identified as one of the factors essential for origin-dependent DNA replication in transient expression assays and has been shown to be involved in late/very late gene expression. To study the function of lef-2 in the life cycle of AcMNPV, lef-2 knockout and repair bacmids were generated by homologous recombination in Escherichia coli. Growth curve analysis showed that lef-2 was essential for virus production. Interestingly, a DNA replication assay indicated that lef-2 is not required for the initiation of viral DNA replication and that, rather, it is required for the amplification of DNA replication. lef-2 is also required for the expression of late and very late genes, as the expression of these genes was abolished by lef-2 deletion. Temporal and spatial distributions of LEF-2 protein in infected cells were also analyzed, and the data showed that LEF-2 protein was localized to the virogenic stroma in the nuclei of the infected cells. Analysis of purified virus particles revealed that LEF-2 is a viral protein component of both budded and occlusion-derived virions, predominantly in the nucleocapsids of the virus particles. This observation suggests that LEF-2 may be required immediately after virus entry into host cells for efficient viral DNA replication.
Wu
Carol P
CP
Department of Chemistry, National Tsing-Hua University, Hsinchu 300, Taiwan, Republic of China.
Huang
Yi-Ju
YJ
Wang
Jen-Yeu
JY
Wu
Yueh-Lung
YL
Lo
Huei-Ru
HR
Wang
Jui-Ching
JC
Chao
Yu-Chan
YC
D000818:Animals; D036022:Capsid Proteins / Q000235:genetics / Q000502:physiology*; D002460:Cell Line; D004279:DNA, Viral / Q000096:biosynthesis*; D017353:Gene Deletion; D015967:Gene Expression Regulation, Viral; D017924:Nucleopolyhedroviruses / Q000235:genetics / Q000502:physiology*; D018411:Spodoptera; D014779:Virus Replication
D036022:Capsid Proteins; D004279:DNA, Viral