A tobacco bZip transcription activator (TAF-1) binds to a G-box-like motif conserved in plant genes.
Tobacco nuclear extract contains a factor that binds specifically to the motif I sequence (5'-GTACGTGGCG-3') conserved among rice rab genes and cotton lea genes. We isolated from a tobacco cDNA expression library, a partial cDNA clone encoding a truncated derivative of a protein designated as TAF-1. The truncated TAF-1 (Mr = 26,000) contains an acidic region at its N-terminus and a bZip motif at its C-terminus. Using a panel of motif I mutants as probes, we showed that the truncated TAF-1 and the tobacco nuclear factor for motif I have similar, it not identical, binding specificities. In particular, both show high-affinity binding to the perfect palindrome 5'-GCCACGTGGC-3' which is also known as the G-box motif. TAF-1 mRNA is highly expressed in root, but the level is at least 10 times lower in stem and leaf. Consistent with this observation, we found that a motif I tetramer, when fused to the -90 derivative of the CaMV 35S promoter, is inactive in leaf of transgenic tobacco. The activity, however, can be elevated by transient expression of the truncated TAF-1. We conclude from these results that TAF-1 can bind to the G-box and related motifs and that it functions as a transcription activator.
Oeda
K
K
Laboratory of Plant Molecular Biology, Rockefeller University, New York 10021-6399.
Salinas
J
J
Chua
N H
NH
D000595:Amino Acid Sequence; D001483:Base Sequence; D022762:CCAAT-Enhancer-Binding Proteins; D003001:Cloning, Molecular; D004268:DNA-Binding Proteins / Q000235:genetics*; D015870:Gene Expression; D005966:Glucuronidase / Q000096:biosynthesis / Q000235:genetics*; D016350:Leucine Zippers / Q000235:genetics*; D051839:NFI Transcription Factors; D009687:Nuclear Proteins / Q000235:genetics*; D010940:Plant Proteins / Q000235:genetics*; D010947:Plants, Toxic; D011485:Protein Binding; D012333:RNA, Messenger / Q000378:metabolism; D012689:Sequence Homology, Nucleic Acid; D014026:Nicotiana / Q000235:genetics*; D015534:Trans-Activators / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D014157:Transcription Factors; D051840:Y-Box-Binding Protein 1
D022762:CCAAT-Enhancer-Binding Proteins; D004268:DNA-Binding Proteins; D051839:NFI Transcription Factors; D009687:Nuclear Proteins; D010940:Plant Proteins; D012333:RNA, Messenger; D015534:Trans-Activators; D014157:Transcription Factors; D051840:Y-Box-Binding Protein 1; C070856:YBX1 protein, human; D005966:Glucuronidase