title: DNA-binding proteins that interact with the long terminal repeat of radiation leukemia virus.
abstract: We used the electrophoretic mobility shift assay to identify the interactions of nuclear proteins with the long terminal repeat of leukemogenic, thymotropic BL/VL3 radiation leukemia virus (RadLV). In the promoter region, we identified a CCAAT box-binding protein (CBP) that has the same binding characteristics as the CCAAT box-binding protein that binds to the Moloney murine sarcoma virus promoter and most likely represents the CP1 factor. In the upstream enhancer region unique to BL/VL3, we detected several sequence-specific complexes, one with T-lymphocyte extracts but not with fibroblast extracts. This U3 region, UEB, may be important for the T-cell specificity of BL/VL3 RadLV. In the enhancer, which has been uniquely rearranged in this virus, we identified three specific protein-binding sites. Two of them showed characteristics of the LVb and core binding sites previously described for other murine retroviruses. But one binding site, identified as Rad-1, is unique to BL/VL3 RadLV and was found downstream, only 1 nucleotide from the core sequence. Rad-1 has a corelike motif on the minus strand, and the factor that binds to it could be competed by a BL/VL3 core-containing fragment. Moreover, the protein-DNA contacts involve the typical three core Gs separated by one T. These results suggest that Rad-1 binds a factor identical or similar to the core-binding factor. Our data suggest that the LVb, core, and Rad-1 motifs may be sufficient for this enhancer, most likely in association with other U3 long terminal repeat sequences, to promote a high rate of transcription of BL/VL3 RadLV in its specific target cells (thymocytes).
authors.affiliation: Laboratory of Molecular Biology, Institut de recherches cliniques de Montréal, Quebec, Canada.
authors.forename: I
authors.initials: I
authors.lastname: Gorska-Flipot
authors.forename: P
authors.initials: P
authors.lastname: Jolicoeur
mesh_terms: D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D004279:DNA, Viral / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism*; D009052:Leukemia Virus, Murine / Q000235:genetics*; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D012091:Repetitive Sequences, Nucleic Acid; D012689:Sequence Homology, Nucleic Acid
chemical_list: D004279:DNA, Viral; D004268:DNA-Binding Proteins