Characterization of Autographa californica nucleopolyhedrovirus immediate early protein ME53: The role of conserved domains in BV production, viral gene transcription, and evidence for ME53 presence at the ribosome

The baculovirus AcMNPV early/late gene me53 is required for efficient BV production and is conserved in all alpha and betabaculoviruses. The 449-amino acid protein contains several highly conserved functionally important domains including two putative C4 zinc finger domains (ZnF-N and ZnF-C) whose cysteine residues are 100% conserved. One purpose of this study is to confirm the presence of two zinc binding domains in ME53, as well as determine their role in virus infection and viral gene transcription. Interestingly, deletion of ZnF-C results in an early delay of BV production from 12 to 18 hours post transfection correlating to ME53's cytoplasmic localization. Cytoplasmic functions at early times post-transfection may include translational regulation, which is supported by yeast-2-hybrid data that ME53 interacts with the host 40S ribosomal subunit protein RACK1. In this study the association of ME53 with the ribosomes of virus infected cells was also investigated.