Optimization of codon usage of poxvirus genes allows for improved transient expression in mammalian cells

John W. Barrett, Yunming Sun, Steven H. Nazarian, Tara A. Belsito, Craig R. Brunetti, Grant McFadden

Research output: Contribution to journalArticlepeer-review

27 Scopus citations


Transient expression of viral genes from certain poxviruses in uninfected mammalian cells can sometimes be unexpectedly inefficient. The reasons for poor expression levels can be due to a number of features of the gene cassette, such as cryptic splice sites, polymerase II termination sequences or motifs that lead to mRNA instability. Here we suggest that in some cases the problem of low protein expression in transfected mammalian cells may be due to inefficient codon usage. We have observed that for many poxvirus genes from the yatapoxvirus genus this deficiency can be overcome by synthesis of the gene with codon sequences optimized for expression in primate cells. This led us to examine colon usage across 2-dozen sequenced members of the Poxviridae. We conclude that codon usage is surprisingly divergent across the different Poxviridae genera but is much more conserved within a single genus. Thus, Poxviridae genera can be divided into distinct groups based on their observed codon bias. When viewed in this context, successful transient expression of transfected poxvirus genes in uninfected mammalian cells can be more accurately predicted based on codon bias. As a corollary, for specific poxvirus genes with less favorable codon usage, codon optimization can result in profoundly increased transient expression levels following transfection of uninfected mammalian cell lines.

Original languageEnglish (US)
Pages (from-to)15-26
Number of pages12
JournalVirus Genes
Issue number1
StatePublished - Aug 2006
Externally publishedYes


  • Codon optimization
  • Codon usage
  • Effective codon number
  • Poxvirus expression
  • Yatapoxvirus

ASJC Scopus subject areas

  • Molecular Biology
  • Genetics
  • Virology


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