Avian endogenous retrovirus EAV-HP shares regions of identity with avian leukosis virus subgroup J and the avian retrotransposon ART-CH.
The existence of novel endogenous retrovirus elements in the chicken genome, designated EAV-HP, with close sequence identity to the env gene of avian leukosis virus (ALV) subgroup J has been reported (L. M. Smith, A. A. Toye, K. Howes, N. Bumstead, L. N. Payne, and K. Venugopal, J. Gen. Virol. 80:261-268, 1999). To resolve the genome structure of these retroviral elements, we have determined the complete sequence of two proviral clones of EAV-HP from a line N chicken genomic DNA yeast artificial chromosome library and from a meat-type chicken line 21 lambda library. The EAV-HP sequences from the two lines were 98% identical and had a typical provirus structure. The two EAV-HP clones showed identical large deletions spanning part of the gag, the entire pol, and part of the env genes. The env region of the EAV-HP clones was 97% identical to the env sequence of HPRS-103, the prototype subgroup J ALV. The 5' region of EAV-HP comprising the R and U5 regions of the long terminal repeat (LTR), the untranslated leader, and the 5' end of the putative gag region were 97% identical to the avian retrotransposon sequence, ART-CH. The remaining gag sequence shared less than 60% identity with other ALV sequences. The U3 region of the LTR was distinct from those of other retroviruses but contained some of the conserved motifs required for functioning as a promoter. To examine the ability of this endogenous retroviral LTR to function as a transcriptional promoter, the EAV-HP and HPRS-103 LTR U3 regions were compared in a luciferase reporter gene assay. The low luciferase activity detected with the EAV-HP LTR U3 constructs, at levels close to those observed for a control vector lacking the promoter or enhancer elements, suggested that these elements function as a weak promoter, possibly accounting for their low expression levels in chicken embryos.
Sacco
M A
MA
Institute for Animal Health, Compton, Newbury, Berkshire RG20 7NN, United Kingdom.
Flannery
D M
DM
Howes
K
K
Venugopal
K
K
D020121:5' Untranslated Regions / Q000235:genetics; D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D001354:Avian Leukosis Virus / Q000145:classification / Q000235:genetics*; D001483:Base Sequence; D002642:Chick Embryo; D020077:Endogenous Retroviruses / Q000235:genetics*; D017353:Gene Deletion; D015752:Genes, env / Q000235:genetics; D015750:Genes, gag / Q000235:genetics; D015751:Genes, pol / Q000235:genetics; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D011533:Proviruses / Q000235:genetics*; D018626:Retroelements / Q000235:genetics*; D012191:Retroviridae Proteins / Q000737:chemistry / Q000235:genetics; D016415:Sequence Alignment; D020079:Terminal Repeat Sequences / Q000235:genetics; D014158:Transcription, Genetic
D020121:5' Untranslated Regions; D018626:Retroelements; D012191:Retroviridae Proteins