A Cellular Drosophila melanogaster Protein with Similarity to Baculovirus F Envelope Fusion Proteins

Abstract

Baculovirus F (fusion) proteins are found in the envelopes of budded virions. Recently a Drosophila melanogaster gene (CG4715) that encodes a protein with sequence similarity to baculovirus F proteins was discovered. To examine similarities and differences with baculovirus F proteins, we cloned the D. melanogaster cellular F (Dm-cF) protein gene and analyzed Dm-cF expression and localization. The predicted Dm-cF protein sequence lacks a furin cleavage site, and transiently expressed Dm-cF showed no protein cleavage and no detectable membrane fusion activity. In cell localization studies, transiently expressed Dm-cF was localized to intracellular organelles in D. melanogaster S2 cells, unlike baculovirus F proteins, which localize to cellular plasma membranes. Using reverse transcriptase PCR and Western blot analysis to examine Dm-cF expression in animals, we detected Dm-cF expression in both larval and adult D. melanogaster cells. However, Dm-cF expression was detected only in third instar larvae and adults, suggesting that Dm-cF expression may be developmentally regulated. We also identified genes related to Dm-cF in the genomes of two other Drosophila species, Drosophila yakuba and Drosophila pseudoobscura, and the mosquito Anopheles gambiae. These observations suggest that f genes may be present in the genomes of many insects. Conservation within and between 22 baculovirus and 4 insect F proteins was examined in detail. These studies demonstrate that Dm-cF is expressed in D. melanogaster and suggest that if baculovirus f genes are derived from a host cellular f gene, the function appears to have changed substantially upon adaptation to the baculovirus infection cycle.

Positive Selection of Iris, a Retroviral Envelope–Derived Host Gene in Drosophila melanogaster

“…(B) An “expected” phylogeny of Drosophila species is shown, summarizing results from many genes [30,31]. …”

“…Compared to mammalian genomes, Drosophila genomes have a higher rate of DNA loss [29], thus proviral sequences are more likely to reflect recent insertion events or insertions that have been selectively retained. In our survey, we unexpectedly found that the D. melanogaster genome contains a host gene, CG4715 (renamed Iris in this paper), which is homologous to the env genes from baculoviruses and insect retroviruses (also identified in [22] [30]). We have now investigated the evolution of Iris in insect genomes, and found it to be conserved in most Drosophila species of the Sophophora subgenus.…”

Genomic comparison of Neodiprion sertifer and Neodiprion lecontei nucleopolyhedroviruses and identification of potential hymenopteran baculovirus-specific open reading frames

“…There is evidence that several baculovirus genes have been transferred horizontally from eukaryotes, possibly from their hosts or bacterial sources (Hughes & Friedman, 2003). Some genes originally derived from a host may have different functions in the virus due to viral adaptation, as was found recently for the baculovirus F protein (Lung & Blissard, 2005).…”

The Baculoviruses Occlusion‐Derived Virus: Virion Structure and Function

“…It has been postulated that gp64 was acquired during baculovirus evolution (Pearson et al, 2000) and it is established that GP64 is not present in ODV envelopes (Hohmann and Faulkner, 1983;Keddie et al, 1989;Wang and Kelly, 1985). The gp64 gene has a common origin with tick-transmitted mammalian arboviruses (Morse et al, 1992) while the f protein gene has an insect origin (Lung and Blissard, 2005). The different origins of these proteins would influence how they function in the virus.…”