Characterization of a family of related cellular transcription factors which can modulate human immunodeficiency virus type 1 transcription in vitro.
LBP-1 is a cellular protein which binds strongly to sequences around the human immunodeficiency virus type 1 (HIV-1) initiation site and weakly over the TATA box. We have previously shown that LBP-1 represses HIV-1 transcription by inhibiting the binding of TFIID to the TATA box. Four similar but distinct cDNAs encoding LBP-1 (LBP-1a, -b, -c, and -d) have been isolated. These are products of two related genes, and each gene encodes two alternatively spliced products. Comparison of the amino acid sequence of LBP-1 with entries in the available protein data bases revealed the identity of LBP-1c to alpha-CP2, an alpha-globin transcription factor. These proteins are also homologous to Drosophila melanogaster Elf-1/NTF-1, an essential transcriptional activator that functions during Drosophila embryogenesis. Three of the recombinant LBP-1 isoforms show DNA binding specificity identical to that of native LBP-1 and bind DNA as a multimer. In addition, antisera raised against recombinant LBP-1 recognize native LBP-1 from HeLa nuclear extract. Functional analyses in a cell-free transcription system demonstrate that recombinant LBP-1 specifically represses transcription from a wild-type HIV-1 template but not from an LBP-1 mutant template. Moreover, LBP-1 can function as an activator both in vivo and in vitro, depending on the promoter context. Interestingly, one isoform of LBP-1 which is missing the region of the Elf-1/NTF-1 homology is unable to bind DNA itself and, presumably through heteromer formation, inhibits binding of the other forms of LBP-1, suggesting that it may function as a dominant negative regulator.
Yoon
J B
JB
Laboratory of Biochemistry and Molecular Biology, Rockefeller University, New York, New York 10021.
Li
G
G
Roeder
R G
RG
D000595:Amino Acid Sequence; D001483:Base Sequence; D001665:Binding Sites; D003001:Cloning, Molecular; D017931:DNA Primers / Q000737:chemistry; D004268:DNA-Binding Proteins / Q000235:genetics*; D015967:Gene Expression Regulation, Viral; D005796:Genes; D015497:HIV-1 / Q000235:genetics*; D006367:HeLa Cells; D006801:Humans; D008969:Molecular Sequence Data; D011994:Recombinant Proteins; D012097:Repressor Proteins / Q000235:genetics*; D015183:Restriction Mapping; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D014157:Transcription Factors / Q000235:genetics*; D014158:Transcription, Genetic
D017931:DNA Primers; D004268:DNA-Binding Proteins; D011994:Recombinant Proteins; D012097:Repressor Proteins; D014157:Transcription Factors; C085968:UBP1 protein, human