Poxvirus Vascular Endothelial Growth Factor (VEGF) Homologs of Orf Virus

4 Pages·0.166 MB·English

by  McFadden G., Moyer R.

Poxvirus Vascular
Endothelial Growth
Factor (VEGF)
Homologs of Orf Virus
Grant McFadden1,* and Richard Moyer2
1The John P. Robarts Research Institute and Department of Microbiology and Immunology,
The University of Western Ontario, 1400 Western Road, London, Ontario, N6G 2V4, Canada
2Department of Molecular Genetics and Microbiology, University of Florida College of Medicine,
PO Box 100266, Gainesville, FL 32610-0266, USA
*corresponding author tel: [phone], fax: [phone], e-mail: [email protected]
DOI: 10.1006/rwcy.2000.03015.
SUMMARY distinct orthopoxvirus genus (36% G+C) (vaccinia
virus Copenhagen, 192kb, smallpox variola virus
(Bangladesh), 186kb) and exhibits a rather narrow
Todate,aviralhomologofvascularendothelialgrowth
host range (Gassmann et al., 1985; Robinson et al.,
factor (VEGF) has been discovered in only one pox-
1987).TwodistinctOVVEGFgenesareknown.They
virus,namelyorfvirusofsheep.Orfvirusencodestwo
werediscoveredinitiallybyroutinesequencingderived
such proteins, each of which possesses characteristic
from New Zealand isolates, strains NZ2 and NZ7
cysteinespacingmotifsfoundincellularVEGFfamily
respectively(Lyttleetal.,1994).TheNZ2geneencodes
members.ViralVEGFbindstothemembersofthesame
a 133 amino acid (14.7kDa) polypeptide; the NZ7
family of cell surface receptors as its cellular counter-
geneencodesa148aminoacid(15kDa)polypeptide.
partsandhasproangiogenicactivity.
Structure
BACKGROUND
NZ2 and NZ7 are contiguous genes lacking introns.
Discovery
Main activities and
Orfvirus(OV)isamemberoftheparapoxvirusgenus,
pathophysiological roles
a group of poxviruses which primarily infect ungu-
latesandlivestock(RobinsonandBalassu,1981).The
virus causes contagious pustular dermatitis in sheep The role of the two viral genes within the context of
and goats and can be transmitted to humans (Mercer the individual viruses is believed to be similar and
et al., 1997). The 139kb OV genome, typical of para- responsible for the marked increase in capillary
poxviruses, is somewhat smaller and more G+C rich endothelial proliferation seen in the dermis following
(63%)thanpoxvirusesofthemorewidelystudiedand infection (Balassu and Robinson, 1987).
806 Grant McFadden and Richard Moyer
GENE AND GENE REGULATION Genepept:
NZ2: 1718158
Accession numbers NZ7: 1718159
NZ2 VEGF: S67520 Sequence
NZ7 VEGF: S67522
See Figure 1.
Chromosome location
Description of protein
The NZ7 and NZ2 VEGF genes are colocated in a
similar region of the viral chromosome in both The two OV VEGF genes are derived from two
viruses. Unlike the gene designation for the ortho- distinctOVviruses.Thetwoproteinsare73%similar
poxviruses, which is based on the HindIII restriction and41%identicaltoeachother.TheNZ7geneis148
map, the OV virus map is based in a BamHI amino acids, the NZ2 gene 133 amino acids. No
restriction map (Fleming et al., 1993). The largest introns are found in poxvirus genes.
viralDNAfragmentresultingfromBamHIdigestion, Both proteins have homology to the VEGF family
the BamHI A fragment, is located at the right most andtheBchainoftherelatedplatelet-derivedgrowth
region of the OV genome, and includes a portion of factor (PDGF) family and the v-sis gene of simian
the inverted terminal repeat sequence found at both sarcoma virus. Both OV proteins also share a
left and right extremes of the viral DNA. This region sequence of N-terminal hydrophobic residues pre-
of the OV genome is the most divergent between the cededby alysine at residue 2, aputative cleavagesite
NZ2andNZ7strains.TheA1R,A2R,andA3Ropen at residues 20—22 (Ala-Asp-Ser) in the NZ2 protein
readingframesarethefirstthreeORFs,readingfrom and the sequence (Ser-Gln-Ser) at residues 25—27 in
right to left, in the BamHI A fragment. The the NZ7 protein. The remaining sequence of both
designation ‘R’ refers to the direction of transcrip- proteins contains a region homologous to the v-sis
tion, which is from left to right. The VEGF genes minimal transforming region, which is conserved in
compriseORFA2.OrfA3Risrelatedtothe30 endof all members of the VEGF family. This minimal
the vaccinia gene F9L. transformingsequenceofthetwoOVVEGFproteins
retains the eight cysteine residues conserved in
VEGF, two of which are needed for dimerization
Regulatory sites and corresponding
andfunctionality(aminoacids114—114NZ2VEGF,
transcription factors 130—132 NZ7 VEGF). A single N-linked glycosyla-
tion site is present (amino acids 85—87 NZ2 VEGF,
95—97 NZ7 VEGF). The glycosylation sites align
Expression of the VEGF gene is ‘early’, before viral
with those in cellular VEGFs. Missing in both
DNA replication.
proteinsarefourblocksofsequencecorrespondingto
the proposed central four exons in the human VEGF
gene, including the highly basic sequence of 24
Cells and tissues that express the
residues shown to be responsible for the cell-
gene associated forms of human VEGF.
Poxvirus gene expression is independent of the
Important homologies
infected cell.
See Table 1.
PROTEIN
Posttranslational modifications
Accession numbers
Potential N-terminal cleavage at amino acids 22—22
GenBank: in NZ2 VEGF, 25—27 in NZ7 VEGF; N-linked
NZ2: S67520 glycosylationsite atNZ2 VEGF amino acids85—87,
NZ7: S67522 NZ7 amino acids 95—97.
Poxvirus Vascular Endothelial Growth Factor (VEGF) Homologs of Orf Virus 807
Figure 1 Alignment of NZ7, NZ2, and v-sis from simian sarcoma virus.
Table 1 Comparative homologies of NZ2 and NZ7 VEGF proteins to various mammalian VEGFs showing
similarities and identities
NZ2 NZ7 Human Rat Guinea pig Human
VEGF VEGF VEGF VEGF VEGF placental
VEGF
NZ2 VEGF
Similarities — 73.3 56.6 50.3 43.8 55.3
Identities — 41.1 28.5 24.6 24.6 27.5
NZ7 VEGF
Similarities 73.3 — 60.1 51.7 43.7 57.9
Identities 41.1 — 23.0 19.0 16.1 19.6
ExtractedfromdataofLyttleetal.(1994).
RECEPTOR UTILIZATION
and induces receptor autophosphorylation, but does
notbindtotheVEGFreceptor1(Flt-1)(Ogawaetal.,
The NZ7 VEGF ligand is expressed as a 20kDa 1998). The viral ligand cannot bind heparin, but
dimer that binds to VEGF receptor 2 (KDR/Flk-1) exhibits comparable ability to stimulate primary
808 Grant McFadden and Richard Moyer
endothelial cells into mitosis and induces vascular infectiousvirusproductionandanalysisofvirionpolypeptides.
permeability as well as the cellular VEGF. Arch.Virol.97,267—281.
Fleming, S. B., Blok, J., Fraser, K. M., Mercer, A. A., and
Robinson, A. J. (1993). Conservation of gene structure and
arrangement between vaccinia and orf virus. Virology 195,
IN VIVO BIOLOGICAL 175—184.
Gassmann, U., Wyler, R., and Wittek, R. (1985). Analysis of
ACTIVITIES OF LIGANDS IN
parpoxvirusgenomes.Arch.Virol.83,17—31.
ANIMAL MODELS Lyttle, D. J., Fraser, K. M., Fleming, S. B., Mercer, A. A., and
Robinson, A. J. (1994). Homologs of vascular endothelial
growth factor are encoded by the poxvirus ORF virus.
Normal physiological roles
J.Virol.68,84—92.
Mercer,A.,Fleming,S.,Robinson,A.,Nettleton,P.,andReid,H.
(1997).Moleculargeneticanalysesofparpoxvirusespathogenic
It is believed that the protein functions to induce the
forhumans.Arch.Virol.13,25—34.
marked capillary endothelial cell proliferation seen in
Ogawa,S.,Oku,A.,Sawano,A.,Yamaguchi,S.,Yazaki,Y.,and
the dermis, as well as the dilatation and dermal Shibuya,M.(1998).Anoveltypeofvascularendothelialgrowth
swelling seen in histological sections of lesions factor, VEGF-E (NZ-7 VEGF), preferentially utilizes KDR/
following OV infection. FLK-1 receptor and carries a potent mitotic activity without
heparin-bindingdomain.J.Biol.Chem.273,31273—31282.
Robinson, A. J., and Balassu, T. C. (1981). Contagious pustular
dermatitis(orf).Vet.Bull.51,771—779.
References Robinson, A. J., Barns, G., Fraser, K., Carpenter, E., and
Mercer, A. A. (1987). Conservation and variation in orf virus
genomes.Virology157,13—23.
Balassu, T. C., and Robinson, A. J. (1987). Orf virus replication
in bovine testis cells: kinetics of viral DNA, polypeptide, and