title: Transcriptional initiation and postinitiation effects of murine leukemia virus long terminal repeat R-region sequences.
abstract: Sequences within the R components of the long terminal repeats (LTRs) of several retroviruses are known to be involved at various steps in expression of the viral genomes. A series of experiments was performed to test whether sequences within the R regions of the murine leukemia viruses Akv and SL3-3 affect viral expression. By using plasmid clones of the viral LTRs linked to a reporter gene, deletion of the R region was found to decrease expression to variable extents in a series of mammalian cell lines, with the largest effects being detected in murine fibroblasts. R-region sequences from the human immunodeficiency virus type 1 LTR or a random sequence were unable to substitute for the murine leukemia virus sequences. Transcripts from the R-region-deleted templates were initiated at the proper site in the LTR, but their levels were decreased at least 10-fold. Nuclear run-on assays showed that the decrease caused by the R-region deletions was due, in part, to an effect on RNA polymerase loading, suggesting an effect on transcriptional initiation. The remainder of the activity was presumably due to a posttranscriptional effect. Analysis of the R-region sequences of murine leukemia viruses and related retroviruses led to the prediction of a conserved secondary structure in the transcribed RNA that might have a role in activity. We conclude that R-region sequences are of importance for the expression of a variety of retroviruses.
authors.affiliation: Department of Molecular Genetics, Albert Einstein College of Medicine, Bronx, New York 10461.
authors.forename: L A
authors.initials: LA
authors.lastname: Cupelli
authors.forename: J
authors.initials: J
authors.lastname: Lenz
mesh_terms: D016475:3T3 Cells; D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D002467:Cell Nucleus / Q000502:physiology; D015500:Chloramphenicol O-Acetyltransferase / Q000235:genetics / Q000378:metabolism; D002872:Chromosome Deletion; D006801:Humans; D009052:Leukemia Virus, Murine / Q000235:genetics*; D051379:Mice; D008815:Mice, Inbred Strains; D008961:Models, Structural; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D009690:Nucleic Acid Conformation; D009838:Oligodeoxyribonucleotides; D010957:Plasmids; D012333:RNA, Messenger / Q000032:analysis / Q000235:genetics; D012091:Repetitive Sequences, Nucleic Acid; D015183:Restriction Mapping; D014158:Transcription, Genetic; D014162:Transfection
chemical_list: D009838:Oligodeoxyribonucleotides; D012333:RNA, Messenger; D015500:Chloramphenicol O-Acetyltransferase