SIRE-1, a copia/Ty1-like retroelement from soybean, encodes a retroviral envelope-like protein.
The soybean genome hosts a family of several hundred, relatively homogeneous copies of a large, copia/Ty1-like retroelement designated SIRE-1. A copy of this element has been recovered from a Glycine max genomic library. DNA sequence analysis of two SIRE-1 subclones revealed that SIRE-1 contains a long, uninterrupted, ORF between the 3' end of the pol ORF and the 3' long terminal repeat (LTR), a region that harbors the env gene in retroviral genomes. Conceptual translation of this second ORF produces a 70-kDa protein. Computer analyses of the amino acid sequence predicted patterns of transmembrane domains, alpha-helices, and coiled coils strikingly similar to those found in mammalian retroviral envelope proteins. In addition, a 65-residue, proline-rich domain is characterized by a strong amino acid compositional bias virtually identical to that of the 60-amino acid, proline-rich neutralization domain of the feline leukemia virus surface protein. The assignment of SIRE-1 to the copia/Ty1 family was confirmed by comparison of the conceptual translation of its reverse transcriptase-like domain with those of other retroelements. This finding suggests the presence of a proretrovirus in a plant genome and is the strongest evidence to date for the existence of a retrovirus-like genome closely related to copia/Ty1 retrotransposons.
Laten
H M
HM
Biology Department, Loyola University Chicago, 6525 North Sheridan Road, Chicago, IL 60626, USA. hlaten@orion.it.luc.edu
Majumdar
A
A
Gaucher
E A
EA
D000595:Amino Acid Sequence; D000818:Animals; D002415:Cats; D003001:Cloning, Molecular; D004251:DNA Transposable Elements / Q000235:genetics*; D018745:Genome, Plant; D016679:Genome, Viral; D008969:Molecular Sequence Data; D012190:Retroviridae / Q000235:genetics*; D016415:Sequence Alignment; D017421:Sequence Analysis; D013025:Glycine max / Q000235:genetics*; D014759:Viral Envelope Proteins / Q000235:genetics*
D004251:DNA Transposable Elements; D014759:Viral Envelope Proteins