title: HERV-F (XA34) is a full-length human endogenous retrovirus expressed in placental and fetal tissues.
abstract: The complete sequence of XA34 was identified from a 107 kb genomic clone originating from the human chromosome 7q31.1-q31.3. The 7.1 kb human endogenous retrovirus (HERV) contains LTR's, gag, pol and env, and a pol sequence which is identical to the 2.3 kb XA34 cDNA clone which we previously isolated from a human glioma cDNA library (Widegren et al., 1996). The HERV is located in a reversed orientation within an intron-sequence of a gene similar to mouse adseverin(D5). The gag and protease regions are intact. However, the pol and env regions are truncated by a deletion which removes the C-terminal end of the integrase and the complete surface protein. The HERV sequence is bordered by a five base-pair direct repeat and has the TG...CA structure. Over the complete HERV genome, XA34 is very similar to members of the HERV-F family and shares the same primer binding site which is homologous to phenylalanine (F) tRNA. Therefore, XA34 is termed HERV-F(XA34). HERV-F(XA34) has an open reading frame (ORF) of 1000 bp in the gag region which starts with Met-Gly in a favorable context and stops in the capsid protein. A strong mRNA expression of HERV-F(XA34) is demonstrated in placental tissue, mainly residing in two transcripts of approximately 7.5 and 8.5-9 kb respectively. Analyses of expressed sequence tags (ESTs) have identified the expression of HERV-F(XA34) sequences in placental tissue, fetal liver/spleen, olfactory epithelium and in an epithelial skin tumor. EST analysis has also identified splice variants of HERV-F(XA34), in which the gag, pol and most of the env regions are spliced out. These splice variants contain a short ORF encoded in the region from the C-terminal portion of env to the 3'-LTR. In addition, ESTs identical to HERV-Fb have been identified in retinal, fetal liver/spleen and brain tissue as well as Jurkat cells. The analyses indicate that the 5'-LTR of HERV-Fb may function as an alternative poly A site of a Krüppel related zinc finger gene (ZNF195).
authors.affiliation: University of Lund, Department of Cell and Molecular Biology, Sweden.
authors.forename: C
authors.initials: C
authors.lastname: Kjellman
authors.forename: H O
authors.initials: HO
authors.lastname: Sjögren
authors.forename: L G
authors.initials: LG
authors.lastname: Salford
authors.forename: B
authors.initials: B
authors.lastname: Widegren
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D015152:Blotting, Northern; D004247:DNA / Q000235:genetics; D020077:Endogenous Retroviruses / Q000235:genetics*; D020224:Expressed Sequence Tags; D005260:Female; D005333:Fetus / Q000378:metabolism*; D015870:Gene Expression; D005814:Genes, Viral; D006801:Humans; D008969:Molecular Sequence Data; D010920:Placenta / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D012689:Sequence Homology, Nucleic Acid; D020079:Terminal Repeat Sequences; D014018:Tissue Distribution
chemical_list: D012333:RNA, Messenger; D004247:DNA