Expression and localization of LEF-11 in Autographa californica nucleopolyhedrovirus-infected Sf9 cells

The Autographa californica multicapsid nucleopolyhedrovirus (AcMNPV) lef-1 I gene was found previously to be necessary to support optimal levels of tr ansient expression from an AcMNPV late promoter. The lef-1 1 gene is unusua l in that it overlaps both upstream (orf38) and downstream (pp31) genes. In this study, the expression and cellular localization of LEF-1 1 were exami ned. The lef-1 1 transcripts were detected from 4 to 36h postinfection (p.i .). The 1-5 kb lef-1 1 mRNA initiates 196 nt upstream of the lef-1 1 transl ation initiation codon, within the upstream orf38 gene. This relatively lon g 5' upstream region encodes a potential small upstream open reading frame (ORF) of 58 amino acids that overlaps the lef-1 I ORF. The 3' end of the le f-1 1 mRNA was mapped as co-terminal with mRNAs from the downstream pp31 ge ne. Using affinity purified anti-LEF-1 1 antibodies, levels of LEF-1 1 expr ession were found to be maximal between approximately 8 and 24 h p.i., alth ough LEF-1 I could be detected as late as 72 h p.i. Using immunofluorescenc e microscopy, it was determined that LEF-1 I localized to dense regions of infected cell nuclei, consistent with its role as a possible late transcrip tion factor.