PubMed Health⌕ Search
Home/Archive/PubMed

PubMed · 7765462

Alphavirus expression systems.

P Liljeström
View original source ↗Export metadata ↓

Abstract

Alphavirus vectors are newcomers in the field of heterologous gene expression. Nevertheless, they have rapidly become popular and are now being used in a wide range of applications. During the past year, new vectors and new methods for their use have improved levels of gene expression. As alphaviruses are capable of infecting humans, biosafety was an important issue during early work with these vectors. The construction of a conditional lethal helper system has now largely overcome this problem, and should further increase the utility of these types of vector in animal cell systems.

Explore related subjects

AlphavirusAnimalsCell LineGene ExpressionGenetic VectorsHumansTransfectionVirus ReplicationJournal ArticleResearch Support, Non-U.S. Gov'tReview

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

P Liljeström. 1994. Alphavirus expression systems.. https://doi.org/10.1016/0958-1669(94)90063-9

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related citations

PubMed1997

Nucleotide sequence of the Barmah Forest virus genome.

Barmah Forest virus (BFV) is an atypical alphavirus [Dalgarno, L., Short, N. J., Hardy, C. M., Bell, J. R., Strauss, J. H., and Marshall, I. D. (1984). Virology 133, 416-426] and has been classified as the sole known member of a seventh alphavirus serocomplex. The complete nucleotide sequence of BFV genomic RNA is 11,488 nucleotides in length excluding the poly(A) tail. Two long open reading frames in the RNA encode a nonstructural polyprotein of 2411 amino acids and a structural polyprotein of 1239 amino acids, respectively. The BFV envelope protein E2 is unique among sequenced alphaviruses in having no N-linked glycosylation sites; E1 carries two glycosylation sites. From amino acid sequence comparisons with sequenced alphaviruses BFV is most closely related to Ross River and Semliki Forest viruses. Sequence homology between BFV and other alphaviruses is relatively uniform along the length of the nonstructural and structural polyproteins, providing no evidence that BFV has arisen from recombination between ancestral alphaviruses in the coding region of the genome. The BFV 3' noncoding region of 445 nucleotides has unusual features. There are two unrelated sequence blocks of 48 nucleotides (sequence I) and 47 nucleotides (sequence II) both of which are repeated once. Sequence I is closely related to a repeat in the 3' noncoding region of Ross River and Getah viruses; sequence II is unrelated to repeat blocks in other sequenced alphaviruses. Thus, recombination between ancestral viruses may have played a role in the evolution of the BFV 3' noncoding region.

Alphavirus↗
PubMed1997

Recombinational history and molecular evolution of western equine encephalomyelitis complex alphaviruses.

Western equine encephalomyelitis (WEE) virus (Togaviridae: Alphavirus) was shown previously to have arisen by recombination between eastern equine encephalomyelitis (EEE)- and Sindbis-like viruses (C. S. Hahn, S. Lustig, E. G. Strauss, and J. H. Strauss, Proc. Natl. Acad. Sci. USA 85:5997-6001, 1988). We have now examined the recombinational history and evolution of all viruses belonging to the WEE antigenic complex, including the Buggy Creek, Fort Morgan, Highlands J, Sindbis, Babanki, Ockelbo, Kyzylagach, Whataroa, and Aura viruses, using nucleotide sequences derived from representative strains. Two regions of the genome were examined: sequences of 477 nucleotides from the C terminus of the E1 envelope glycoprotein gene which in WEE virus was derived from the Sindbis-like virus parent, and 517 nucleotide sequences at the C terminus of the nsP4 gene which in WEE virus was derived from the EEE-like virus parent. Trees based on the E1 region indicated that all members of the WEE virus complex comprise a monophyletic group. Most closely related to WEE viruses are other New World members of the complex: the Highlands J, Buggy Creek, and Fort Morgan viruses. More distantly related WEE complex viruses included the Old World Sindbis, Babanki, Ockelbo, Kyzylagach, and Whataroa viruses, as well as the New World Aura virus. Detailed analyses of 38 strains of WEE virus revealed at least 4 major lineages; two were represented by isolates from Argentina, one was from Brazil, and a fourth contained isolates from many locations in South and North America as well as Cuba. Trees based on the nsP4 gene indicated that all New World WEE complex viruses except Aura virus are recombinants derived from EEE- and Sindbis-like virus ancestors. In contrast, the Old World members of the WEE complex, as well as Aura virus, did not appear to have recombinant genomes. Using an evolutionary rate estimate (2.8 x 10(-4) substitutions per nucleotide per year) obtained from E1-3' sequences of WEE viruses, we estimated that the recombination event occurred in the New World 1,300 to 1,900 years ago. This suggests that the alphaviruses originated in the New World a few thousand years ago.

Alphavirus↗
PubMed1996

Preformed cytoplasmic nucleocapsids are not necessary for alphavirus budding.

According to the present model for assembly of alphaviruses, e.g. Semliki Forest virus (SFV), the viral genome is first encapsidated into a nucleocapsid (NC) in cytoplasm and this is then used for budding at plasma membrane (PM). The preformed NC is thought to act as a template on which the viral envelope can be organized. In the present work we have characterized two SFV deletion mutants which did not assemble NCs in the cytoplasm but which instead appeared to form NCs at the PM simultaneously with virus budding. The deletions were introduced in a conserved 14 residue long linker peptide that joins the amino-terminal RNA-binding domain with the carboxy-terminal serine-protease domain of the capsid protein. Despite the deletions and the change in morphogenesis, wild-type (wt)-like particles were produced with almost wt efficiency. It is suggested that the NC assembly defect of the mutants is rescued through spike-capsid interactions at PM. The results show that the preassembly of NCs in the cytoplasm is not a prerequisite for alphavirus budding. The apparent similarities of the morphogenesis pathways of wt and mutant SFV with those of type D and type C retroviruses are discussed.

Alphavirus↗