Complete sequence of enzootic nasal tumor virus, a retrovirus associated with transmissible intranasal tumors of sheep

Abstract

The sequence of the complete genome of ovine enzootic nasal tumor virus, an exogenous retrovirus associated exclusively with contagious intranasal tumors of sheep, was determined. The genome is 7,434 nucleotides long and exhibits a genetic organization characteristic of type B and D oncoviruses. Enzootic nasal tumor virus is closely related to the Jaagsiekte sheep retrovirus and to sheep endogenous retroviruses.

FIG. 1

Schematic diagram of the ENTV provirus showing (i) sequence derived from cDNA library clones and (ii) PCR products generated to complete the sequencing of ENTV.

FIG. 2

Complete nucleotide sequence of the ENTV genome together with the deduced amino acid sequences of the open reading frames. The limits of U3, R, and U5 are indicated by arrows. The inverted repeats (IR), primer binding site (PBS), and polypurine tract (PPT) are indicated by underlines. The consensus protease cleavage site for env SU and TM is indicated by ∇.

FIG. 2

Complete nucleotide sequence of the ENTV genome together with the deduced amino acid sequences of the open reading frames. The limits of U3, R, and U5 are indicated by arrows. The inverted repeats (IR), primer binding site (PBS), and polypurine tract (PPT) are indicated by underlines. The consensus protease cleavage site for env SU and TM is indicated by ∇.

FIG. 2

Complete nucleotide sequence of the ENTV genome together with the deduced amino acid sequences of the open reading frames. The limits of U3, R, and U5 are indicated by arrows. The inverted repeats (IR), primer binding site (PBS), and polypurine tract (PPT) are indicated by underlines. The consensus protease cleavage site for env SU and TM is indicated by ∇.

FIG. 3

Genetic organization of ENTV. Stop codons in the three reading frames are represented by long vertical bars; methionine residues are represented by short vertical bars.

FIG. 4

Alignment of the LTR sequences of ENTV and JSRV. The JSRV sequence shown is that of York et al. (38). Sequences of the LTR primers are underlined. Gaps in alignment are shown by dashes; dots represents identity.

FIG. 5

Phylogenetic trees of (A) gag and (B) env SU nucleotide sequences of ENTV, baboon endogenous retrovirus (BaERV) (18), bovine immunodeficiency virus (BIV) (11), equine infectious anemia virus (EIAV) (19), JSRV (38), MMTV (24), simian SRV-1 type D retrovirus (SRV-1) (27), MPMV (33), maedi-visna virus (MVV) (28), and Moloney murine leukemia virus (MoMLV) (32). The sequences were aligned by using GCG Eclustalw, and unrooted trees were constructed by the neighbor-joining method of Saitou and Nei (30) (Clustree). Horizontal branch lengths are proportional to evolutionary distances as estimated by percent divergence.