Identification of the Rem-responsive element of mouse mammary tumor virus.
Mouse mammary tumor virus (MMTV) has previously been shown to encode a functional homolog of the human immunodeficiency virus-1 (HIV-1) nuclear export protein Rev, termed Rem. Here, we show that deletion of the rem gene from a MMTV molecular clone interfered with the nucleo-cytoplasmic transport of genomic length viral mRNA and resulted in a loss of viral capsid (Gag) protein production. Interestingly, nuclear export of single-spliced env mRNA was only moderately affected, suggesting that this transcript is, at least to some extent, transported via a distinct, Rem-independent export mechanism. To identify and characterize a cis-acting RNA element required for Rem responsiveness (RmRE), extensive computational and functional analyses were performed. By these means a region of 490 nt corresponding to positions nt 8517-nt 9006 in the MMTV reference strain was identified as RmRE. Deletion of this fragment, which spans the env-U3 junction region, abolished Gag expression. Furthermore, insertion of this sequence into a heterologous HIV-1-based reporter construct restored, in the presence of Rem, HIV-1 Gag expression to levels determined for the Rev/RRE export system. These results clearly demonstrate that the identified region, whose geometry resembles that of other retroviral-responsive elements, is capable to functionally substitute, in the presence of Rem, for Rev/RRE and thus provide unequivocal evidence that MMTV is a complex retrovirus.
Müllner
Matthias
M
Department of Pathobiology, Institute of Virology, University of Veterinary Medicine Vienna, Austria.
Salmons
Brian
B
Günzburg
Walter H
WH
Indik
Stanislav
S
D021581:Active Transport, Cell Nucleus; D000818:Animals; D001665:Binding Sites; D002415:Cats; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D019295:Computational Biology; D017930:Genes, Reporter; D015497:HIV-1 / Q000235:genetics; D008324:Mammary Tumor Virus, Mouse / Q000235:genetics*; D012367:RNA, Viral / Q000737:chemistry* / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000378:metabolism*; D038621:Regulatory Sequences, Ribonucleic Acid; D017384:Sequence Deletion; D014764:Viral Proteins / Q000378:metabolism*; D054301:gag Gene Products, Human Immunodeficiency Virus / Q000235:genetics / Q000378:metabolism
D012367:RNA, Viral; D016601:RNA-Binding Proteins; D038621:Regulatory Sequences, Ribonucleic Acid; D014764:Viral Proteins; D054301:gag Gene Products, Human Immunodeficiency Virus